mirror of
https://github.com/italicsjenga/gba.git
synced 2024-12-23 19:01:30 +11:00
hello world chapter is complete
This commit is contained in:
Lokathor
parent
f838103528
commit
0b9d8e9b29
|
|
@ -30,7 +30,7 @@ do this stuff.
|
|||
dots as well as other support files:
|
||||
* crt0.s
|
||||
* linker.ld
|
||||
* thumbv4-nintendo-agb.json
|
||||
* thumbv4-none-agb.json
|
||||
* build.rs
|
||||
|
||||
5) Run `arm-none-eabi-as crt0.s -o crt0.o` to build the `crt0.s` into a `crt0.o`
|
||||
|
|
@ -38,7 +38,7 @@ do this stuff.
|
|||
`build.bat` file it's set to simply run every single time because it's a
|
||||
cheap enough operation.
|
||||
|
||||
6) Build with `cargo xbuild --target thumbv4-nintendo-agb.json`
|
||||
6) Build with `cargo xbuild --target thumbv4-none-agb.json`
|
||||
* The file extension is significant, and `cargo xbuild` takes it as a flag to
|
||||
compile dependencies with the same sysroot, so you can include crates
|
||||
normally. Well, crates that can run inside a GBA at least (Which means they
|
||||
|
|
@ -47,7 +47,7 @@ do this stuff.
|
|||
helpful because it has debug symbols).
|
||||
|
||||
7) Also you can patch up the output to be a "real" ROM file:
|
||||
* `arm-none-eabi-objcopy -O binary target/thumbv4-nintendo-agb/debug/gbatest target/output.gba`
|
||||
* `arm-none-eabi-objcopy -O binary target/thumbv4-none-agb/debug/gbatest target/output.gba`
|
||||
* `gbafix target/output.gba`
|
||||
|
||||
8) Alternately, you can use the provided `build.bat` file (or write a similar
|
||||
|
|
|
|||
|
|
@ -8,3 +8,4 @@
|
|||
* [IO Registers](ch1/io_registers.md)
|
||||
* [The Display Control](ch1/the_display_control.md)
|
||||
* [Video Memory Intro](ch1/video_memory_intro.md)
|
||||
* [hello2](ch1/hello2.md)
|
||||
|
|
|
|||
|
|
@ -37,10 +37,12 @@ Now you'll need some particular files each time you want to start a new project.
|
|||
You can find them in the root of the [rust-console/gba
|
||||
repo](https://github.com/rust-console/gba).
|
||||
|
||||
* `thumbv4-nintendo-agb.json` describes the overall GBA to cargo-xbuild so it
|
||||
knows what to do. This is actually a somewhat made up target name since
|
||||
there's no official target name, but this is the best name to pick based on
|
||||
[how target names are decided](https://wiki.osdev.org/Target_Triplet).
|
||||
* `thumbv4-none-agb.json` describes the overall GBA to cargo-xbuild so it knows
|
||||
what to do. This is actually a somewhat made up target name since there's no
|
||||
official target name. The GBA is essentially the same as a normal
|
||||
`thumbv4-none-eabi` device, but we give it the "agb" signifier so that later
|
||||
on we'll be able to use rust's `cfg` ability to allow our code to know if it's
|
||||
specifically targeting a GBA or some other similar device (like an NDS).
|
||||
* `crt0.s` describes some ASM startup stuff. If you have more ASM to place here
|
||||
later on this is where you can put it. You also need to build it into a
|
||||
`crt0.o` file before it can actually be used, but we'll cover that below.
|
||||
|
|
@ -57,7 +59,7 @@ Once you've got something to build, you perform the following steps:
|
|||
might as well do it every time so that you never forget to because it's a
|
||||
practically instant operation.
|
||||
|
||||
* `cargo xbuild --target thumbv4-nintendo-agb.json`
|
||||
* `cargo xbuild --target thumbv4-none-agb.json`
|
||||
* This builds your Rust source. It accepts _most of_ the normal options, such
|
||||
as `--release`, and options, such as `--bin foo` or `--examples`, that you'd
|
||||
expect `cargo` to accept.
|
||||
|
|
@ -83,7 +85,7 @@ emulators can also do it.
|
|||
However, if you want a "real" ROM that works in all emulators and that you could
|
||||
transfer to a flash cart there's a little more to do.
|
||||
|
||||
* `arm-none-eabi-objcopy -O binary target/thumbv4-nintendo-agb/MODE/BIN_NAME target/ROM_NAME.gba`
|
||||
* `arm-none-eabi-objcopy -O binary target/thumbv4-none-agb/MODE/BIN_NAME target/ROM_NAME.gba`
|
||||
* This will perform an [objcopy](https://linux.die.net/man/1/objcopy) on our
|
||||
program. Here I've named the program `arm-none-eabi-objcopy`, which is what
|
||||
devkitpro calls their version of `objcopy` that's specific to the GBA in the
|
||||
|
|
@ -97,7 +99,7 @@ transfer to a flash cart there's a little more to do.
|
|||
`cargo` arranges stuff in the `target/` directory, and between RLS and
|
||||
`cargo doc` and stuff it gets kinda crowded, so it goes like this:
|
||||
* Since our program was built for a non-local target, first we've got a
|
||||
directory named for that target, `thumbv4-nintendo-agb/`
|
||||
directory named for that target, `thumbv4-none-agb/`
|
||||
* Next, the "MODE" is either `debug/` or `release/`, depending on if we had
|
||||
the `--release` flag included. You'll probably only be packing release
|
||||
mode programs all the way into GBA roms, but it works with either mode.
|
||||
|
|
|
|||
|
|
@ -177,3 +177,8 @@ If you ever use volatile stuff on other platforms it's important to note that
|
|||
volatile doesn't make things thread-safe, you still need atomic for that.
|
||||
However, the GBA doesn't have threads, so we don't have to worry about thread
|
||||
safety concerns.
|
||||
|
||||
Accordingly, our first bit of code for our library will be a _newtype_ over a
|
||||
normal `*mut T` so that it has volatile reads and writes as the default. We'll
|
||||
cover the details later on when we try writing a `hello2` program, once we know
|
||||
more of what's going on.
|
||||
|
|
|
|||
114
book/src/ch1/hello2.md
Normal file
114
book/src/ch1/hello2.md
Normal file
|
|
@ -0,0 +1,114 @@
|
|||
# hello2
|
||||
|
||||
Okay so let's have a look again:
|
||||
|
||||
`hello1`
|
||||
|
||||
```rust
|
||||
#![feature(start)]
|
||||
#![no_std]
|
||||
|
||||
#[cfg(not(test))]
|
||||
#[panic_handler]
|
||||
fn panic(_info: &core::panic::PanicInfo) -> ! {
|
||||
loop {}
|
||||
}
|
||||
|
||||
#[start]
|
||||
fn main(_argc: isize, _argv: *const *const u8) -> isize {
|
||||
unsafe {
|
||||
(0x04000000 as *mut u16).write_volatile(0x0403);
|
||||
(0x06000000 as *mut u16).offset(120 + 80 * 240).write_volatile(0x001F);
|
||||
(0x06000000 as *mut u16).offset(136 + 80 * 240).write_volatile(0x03E0);
|
||||
(0x06000000 as *mut u16).offset(120 + 96 * 240).write_volatile(0x7C00);
|
||||
loop {}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Now let's clean this up so that it's clearer what's going on.
|
||||
|
||||
First we'll label that display control stuff:
|
||||
|
||||
```rust
|
||||
pub const DISPCNT: *mut u16 = 0x04000000 as *mut u16;
|
||||
pub const MODE3: u16 = 3;
|
||||
pub const BG2: u16 = 0b100_0000_0000;
|
||||
```
|
||||
|
||||
Next we make some const values for the actual pixel drawing
|
||||
|
||||
```rust
|
||||
pub const VRAM: usize = 0x06000000;
|
||||
pub const SCREEN_WIDTH: isize = 240;
|
||||
```
|
||||
|
||||
And then we want a small helper function for putting together a color value.
|
||||
|
||||
Happily, this one can even be declared as a const function. At the time of
|
||||
writing, we've got the "minimal const fn" support in nightly. It really is quite
|
||||
limited, but I'm happy to let rustc and LLVM pre-compute as much as they can
|
||||
when it comes to the GBA's tiny CPU.
|
||||
|
||||
```rust
|
||||
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
|
||||
blue << 10 | green << 5 | red
|
||||
}
|
||||
```
|
||||
|
||||
Finally, we'll make a function for drawing a pixel in Mode 3. Even though it's
|
||||
just a one-liner, having the "important parts" be labeled as function arguments
|
||||
usually helps you think about it a lot better.
|
||||
|
||||
```rust
|
||||
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
|
||||
(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write_volatile(color);
|
||||
}
|
||||
```
|
||||
|
||||
So now we've got this:
|
||||
|
||||
`hello2`
|
||||
|
||||
```rust
|
||||
#![feature(start)]
|
||||
#![no_std]
|
||||
|
||||
#[cfg(not(test))]
|
||||
#[panic_handler]
|
||||
fn panic(_info: &core::panic::PanicInfo) -> ! {
|
||||
loop {}
|
||||
}
|
||||
|
||||
#[start]
|
||||
fn main(_argc: isize, _argv: *const *const u8) -> isize {
|
||||
unsafe {
|
||||
DISPCNT.write_volatile(MODE3 | BG2);
|
||||
mode3_pixel(120, 80, rgb16(31, 0, 0));
|
||||
mode3_pixel(136, 80, rgb16(0, 31, 0));
|
||||
mode3_pixel(120, 96, rgb16(0, 0, 31));
|
||||
loop {}
|
||||
}
|
||||
}
|
||||
|
||||
pub const DISPCNT: *mut u16 = 0x04000000 as *mut u16;
|
||||
pub const MODE3: u16 = 3;
|
||||
pub const BG2: u16 = 0b100_0000_0000;
|
||||
|
||||
pub const VRAM: usize = 0x06000000;
|
||||
pub const SCREEN_WIDTH: isize = 240;
|
||||
|
||||
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
|
||||
blue << 10 | green << 5 | red
|
||||
}
|
||||
|
||||
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
|
||||
(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write_volatile(color);
|
||||
}
|
||||
```
|
||||
|
||||
Exact same program that we started with, but much easier to read.
|
||||
|
||||
Of course, in the full `gba` crate that this book is a part of we have these and
|
||||
other elements all labeled and sorted out for you. Still, for educational
|
||||
purposes it's often best to do it yourself at least once.
|
||||
|
|
@ -27,9 +27,10 @@ own demos and chapters later on, so that's all we'll say about them for now.
|
|||
Modes 3, 4, and 5 are "Bitmap" modes. These let you write individual pixels to
|
||||
locations on the screen.
|
||||
|
||||
* **Mode 3** is full resolution (240w x 160h) RBG15 color. You might not be used to
|
||||
RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
|
||||
bits for each color channel, and the highest bit is totally ignored.
|
||||
* **Mode 3** is full resolution (240w x 160h) RBG15 color. You might not be used
|
||||
to RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
|
||||
bits for each color channel stored within a `u16` value, and the highest bit is
|
||||
simply ignored.
|
||||
* **Mode 4** is full resolution paletted color. Instead of being a `u16` color, each
|
||||
pixel value is a `u8` palette index entry, and then the display uses the
|
||||
palette memory (which we'll talk about later) to store the actual color data.
|
||||
|
|
@ -99,3 +100,6 @@ First let's [convert that to
|
|||
binary](https://www.wolframalpha.com/input/?i=0x0403), and we get
|
||||
`0b100_0000_0011`. So, that's setting Mode 3 with background 2 enabled and
|
||||
nothing else special.
|
||||
|
||||
However, I think we can do better than that. This is a prime target for more
|
||||
newtyping as we attempt a `hello2` program.
|
||||
|
|
|
|||
|
|
@ -18,20 +18,96 @@ don't know to follow the special rules.
|
|||
|
||||
## RGB15
|
||||
|
||||
TODO
|
||||
As I said before, RGB15 stores a color within a `u16` value using 5 bits for
|
||||
each color channel.
|
||||
|
||||
```rust
|
||||
pub const RED: u16 = 0b0_00000_00000_11111;
|
||||
pub const GREEN: u16 = 0b0_00000_11111_00000;
|
||||
pub const BLUE: u16 = 0b0_11111_00000_00000;
|
||||
```
|
||||
|
||||
In Mode 3 and Mode 5 we write direct color values into VRAM, and in Mode 4 we
|
||||
write palette index values, and then the color values go into the PALRAM.
|
||||
|
||||
## Mode 3
|
||||
|
||||
TODO
|
||||
Mode 3 is pretty easy. We have a full resolution grid of rgb15 pixels. There's
|
||||
160 rows of 240 pixels each, with the base address being the top left corner. A
|
||||
particular pixel uses normal "2d indexing" math:
|
||||
|
||||
```rust
|
||||
let row_five_col_seven = 5 + (7 * SCREEN_WIDTH);
|
||||
```
|
||||
|
||||
To draw a pixel, we just write a value at the address for the row and col that
|
||||
we want to draw to.
|
||||
|
||||
## Mode 4
|
||||
|
||||
TODO
|
||||
Mode 4 introduces page flipping. Instead of one giant page at `0x0600_0000`,
|
||||
there's Page 0 at `0x0600_0000` and then Page 1 at `0x0600_A000`. The resolution
|
||||
for each page is the same as above, but instead of writing `u16` values, the
|
||||
memory is treated as `u8` indexes into PALRAM. The PALRAM starts at
|
||||
`0x0500_0000`, and there's enough space for 256 palette entries (each a `u16`).
|
||||
|
||||
To set the color of a palette entry we just do a normal `u16` write_volatile.
|
||||
|
||||
```rust
|
||||
(0x0500_0000 as *mut u16).offset(target_index).write_volatile(new_color)
|
||||
```
|
||||
|
||||
To draw a pixel we set the palette entry that we want the pixel to use. However,
|
||||
we must remember the "minimum size" write limitation that applies to VRAM. So,
|
||||
if we want to change just a single pixel at a time we must
|
||||
|
||||
1) Read the full `u16` it's a part of.
|
||||
2) Clear the half of the `u16` we're going to replace
|
||||
3) Write the half of the `u16` we're going to replace with the new value
|
||||
4) Write that result back to the address.
|
||||
|
||||
So, the math for finding a byte offset is the same as Mode 3 (since they're both
|
||||
a 2d grid). If the byte offset is EVEN it'll be the high bits of the `u16` at
|
||||
half the byte offset rounded down. If the offset is ODD it'll be the low bits of
|
||||
the `u16` at half the byte.
|
||||
|
||||
Does that make sense?
|
||||
|
||||
* If we want to write pixel (0,0) the byte offset is 0, so we change the high
|
||||
bits of `u16` offset 0. Then we want to write to (1,0), so the byte offset is
|
||||
1, so we change the low bits of `u16` offset 0. The pixels are next to each
|
||||
other, and the target bytes are next to each other, good so far.
|
||||
* If we want to write to (5,6) that'd be byte `5 + 6 * 240 = 1445`, so we'd
|
||||
target the low bits of `u16` offset `floor(1445/2) = 722`.
|
||||
|
||||
As you can see, trying to write individual pixels in Mode 4 is mostly a bad
|
||||
time. Fret not! We don't _have_ to write individual bytes. If our data is
|
||||
arranged correctly ahead of time we can just write `u16` or `u32` values
|
||||
directly. The video hardware doesn't care, it'll get along just fine.
|
||||
|
||||
## Mode 5
|
||||
|
||||
TODO
|
||||
Mode 5 is also a two page mode, but instead of compressing the size of a pixel's
|
||||
data to fit in two pages, we compress the resolution.
|
||||
|
||||
Mode 5 is full `u16` color, but only 160w x 128h per page.
|
||||
|
||||
## In Conclusion...
|
||||
|
||||
TODO
|
||||
So what got written into VRAM in `hello1`?
|
||||
|
||||
```rust
|
||||
(0x06000000 as *mut u16).offset(120 + 80 * 240).write_volatile(0x001F);
|
||||
(0x06000000 as *mut u16).offset(136 + 80 * 240).write_volatile(0x03E0);
|
||||
(0x06000000 as *mut u16).offset(120 + 96 * 240).write_volatile(0x7C00);
|
||||
```
|
||||
|
||||
So at pixels `(120,80)`, `(136,80)`, and `(120,96)` we write three values. Once
|
||||
again we probably need to [convert them](https://www.wolframalpha.com/) into
|
||||
binary to make sense of it.
|
||||
|
||||
* 0x001F: 0b11111
|
||||
* 0x03E0: 0b11111_00000
|
||||
* 0x7C00: 0b11111_00000_00000
|
||||
|
||||
Ah, of course, a red pixel, a green pixel, and a blue pixel.
|
||||
|
|
|
|||
|
|
@ -3,12 +3,12 @@
|
|||
arm-none-eabi-as crt0.s -o crt0.o
|
||||
|
||||
@rem Build all examples, both debug and release
|
||||
cargo xbuild --examples --target thumbv4-nintendo-agb.json
|
||||
cargo xbuild --examples --target thumbv4-nintendo-agb.json --release
|
||||
cargo xbuild --examples --target thumbv4-none-agb.json
|
||||
cargo xbuild --examples --target thumbv4-none-agb.json --release
|
||||
|
||||
@echo Packing examples into ROM files...
|
||||
@for %%I in (.\examples\*.*) do @(
|
||||
echo %%~nI
|
||||
arm-none-eabi-objcopy -O binary target/thumbv4-nintendo-agb/release/examples/%%~nI target/example-%%~nI.gba >nul
|
||||
arm-none-eabi-objcopy -O binary target/thumbv4-none-agb/release/examples/%%~nI target/example-%%~nI.gba >nul
|
||||
gbafix target/example-%%~nI.gba >nul
|
||||
)
|
||||
|
|
|
|||
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html" class="active"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html" class="active"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="../ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
@ -169,8 +169,12 @@ cargo will figure it all out for you.</p>
|
|||
You can find them in the root of the <a href="https://github.com/rust-console/gba">rust-console/gba
|
||||
repo</a>.</p>
|
||||
<ul>
|
||||
<li><code>thumbv4-nintendo-agb.json</code> describes the overall GBA to cargo-xbuild so it knows
|
||||
what to do.</li>
|
||||
<li><code>thumbv4-none-agb.json</code> describes the overall GBA to cargo-xbuild so it knows
|
||||
what to do. This is actually a somewhat made up target name since there's no
|
||||
official target name. The GBA is essentially the same as a normal
|
||||
<code>thumbv4-none-eabi</code> device, but we give it the "agb" signifier so that later
|
||||
on we'll be able to use rust's <code>cfg</code> ability to allow our code to know if it's
|
||||
specifically targeting a GBA or some other similar device (like an NDS).</li>
|
||||
<li><code>crt0.s</code> describes some ASM startup stuff. If you have more ASM to place here
|
||||
later on this is where you can put it. You also need to build it into a
|
||||
<code>crt0.o</code> file before it can actually be used, but we'll cover that below.</li>
|
||||
|
|
@ -190,7 +194,7 @@ practically instant operation.</li>
|
|||
</ul>
|
||||
</li>
|
||||
<li>
|
||||
<p><code>cargo xbuild --target thumbv4-nintendo-agb.json</code></p>
|
||||
<p><code>cargo xbuild --target thumbv4-none-agb.json</code></p>
|
||||
<ul>
|
||||
<li>This builds your Rust source. It accepts <em>most of</em> the normal options, such
|
||||
as <code>--release</code>, and options, such as <code>--bin foo</code> or <code>--examples</code>, that you'd
|
||||
|
|
@ -219,7 +223,7 @@ emulators can also do it.</p>
|
|||
transfer to a flash cart there's a little more to do.</p>
|
||||
<ul>
|
||||
<li>
|
||||
<p><code>arm-none-eabi-objcopy -O binary target/thumbv4-nintendo-agb/MODE/BIN_NAME target/ROM_NAME.gba</code></p>
|
||||
<p><code>arm-none-eabi-objcopy -O binary target/thumbv4-none-agb/MODE/BIN_NAME target/ROM_NAME.gba</code></p>
|
||||
<ul>
|
||||
<li>This will perform an <a href="https://linux.die.net/man/1/objcopy">objcopy</a> on our
|
||||
program. Here I've named the program <code>arm-none-eabi-objcopy</code>, which is what
|
||||
|
|
@ -235,7 +239,7 @@ bare memory dump of the program.</li>
|
|||
<code>cargo doc</code> and stuff it gets kinda crowded, so it goes like this:
|
||||
<ul>
|
||||
<li>Since our program was built for a non-local target, first we've got a
|
||||
directory named for that target, <code>thumbv4-nintendo-agb/</code></li>
|
||||
directory named for that target, <code>thumbv4-none-agb/</code></li>
|
||||
<li>Next, the "MODE" is either <code>debug/</code> or <code>release/</code>, depending on if we had
|
||||
the <code>--release</code> flag included. You'll probably only be packing release
|
||||
mode programs all the way into GBA roms, but it works with either mode.</li>
|
||||
|
|
|
|||
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html" class="active"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html" class="active"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="../ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
@ -293,6 +293,10 @@ write to <code>d</code> will <em>always</em> happen after the write to <code>c</
|
|||
volatile doesn't make things thread-safe, you still need atomic for that.
|
||||
However, the GBA doesn't have threads, so we don't have to worry about thread
|
||||
safety concerns.</p>
|
||||
<p>Accordingly, our first bit of code for our library will be a <em>newtype</em> over a
|
||||
normal <code>*mut T</code> so that it has volatile reads and writes as the default. We'll
|
||||
cover the details later on when we try writing a <code>hello2</code> program, once we know
|
||||
more of what's going on.</p>
|
||||
|
||||
</main>
|
||||
|
||||
|
|
|
|||
289
docs/ch1/hello2.html
Normal file
289
docs/ch1/hello2.html
Normal file
|
|
@ -0,0 +1,289 @@
|
|||
<!DOCTYPE HTML>
|
||||
<html lang="en" class="sidebar-visible no-js">
|
||||
<head>
|
||||
<!-- Book generated using mdBook -->
|
||||
<meta charset="UTF-8">
|
||||
<title>hello2 - Rust GBA Tutorials</title>
|
||||
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
|
||||
<meta name="description" content="">
|
||||
<meta name="viewport" content="width=device-width, initial-scale=1">
|
||||
<meta name="theme-color" content="#ffffff" />
|
||||
|
||||
<link rel="shortcut icon" href="../favicon.png">
|
||||
<link rel="stylesheet" href="../css/variables.css">
|
||||
<link rel="stylesheet" href="../css/general.css">
|
||||
<link rel="stylesheet" href="../css/chrome.css">
|
||||
<link rel="stylesheet" href="../css/print.css" media="print">
|
||||
|
||||
<!-- Fonts -->
|
||||
<link rel="stylesheet" href="../FontAwesome/css/font-awesome.css">
|
||||
<link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css">
|
||||
<link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css">
|
||||
|
||||
<!-- Highlight.js Stylesheets -->
|
||||
<link rel="stylesheet" href="../highlight.css">
|
||||
<link rel="stylesheet" href="../tomorrow-night.css">
|
||||
<link rel="stylesheet" href="../ayu-highlight.css">
|
||||
|
||||
<!-- Custom theme stylesheets -->
|
||||
|
||||
|
||||
|
||||
</head>
|
||||
<body class="light">
|
||||
<!-- Provide site root to javascript -->
|
||||
<script type="text/javascript">var path_to_root = "../";</script>
|
||||
|
||||
<!-- Work around some values being stored in localStorage wrapped in quotes -->
|
||||
<script type="text/javascript">
|
||||
try {
|
||||
var theme = localStorage.getItem('mdbook-theme');
|
||||
var sidebar = localStorage.getItem('mdbook-sidebar');
|
||||
|
||||
if (theme.startsWith('"') && theme.endsWith('"')) {
|
||||
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
|
||||
}
|
||||
|
||||
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
|
||||
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
|
||||
}
|
||||
} catch (e) { }
|
||||
</script>
|
||||
|
||||
<!-- Set the theme before any content is loaded, prevents flash -->
|
||||
<script type="text/javascript">
|
||||
var theme;
|
||||
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
|
||||
if (theme === null || theme === undefined) { theme = 'light'; }
|
||||
document.body.className = theme;
|
||||
document.querySelector('html').className = theme + ' js';
|
||||
</script>
|
||||
|
||||
<!-- Hide / unhide sidebar before it is displayed -->
|
||||
<script type="text/javascript">
|
||||
var html = document.querySelector('html');
|
||||
var sidebar = 'hidden';
|
||||
if (document.body.clientWidth >= 1080) {
|
||||
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
|
||||
sidebar = sidebar || 'visible';
|
||||
}
|
||||
html.classList.remove('sidebar-visible');
|
||||
html.classList.add("sidebar-" + sidebar);
|
||||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="../ch1/hello2.html" class="active"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
||||
<div class="page">
|
||||
|
||||
<div id="menu-bar" class="menu-bar">
|
||||
<div id="menu-bar-sticky-container">
|
||||
<div class="left-buttons">
|
||||
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
|
||||
<i class="fa fa-bars"></i>
|
||||
</button>
|
||||
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
|
||||
<i class="fa fa-paint-brush"></i>
|
||||
</button>
|
||||
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
|
||||
<li role="none"><button role="menuitem" class="theme" id="light">Light <span class="default">(default)</span></button></li>
|
||||
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
|
||||
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
|
||||
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
|
||||
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
|
||||
</ul>
|
||||
|
||||
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
|
||||
<i class="fa fa-search"></i>
|
||||
</button>
|
||||
|
||||
</div>
|
||||
|
||||
<h1 class="menu-title">Rust GBA Tutorials</h1>
|
||||
|
||||
<div class="right-buttons">
|
||||
<a href="../print.html" title="Print this book" aria-label="Print this book">
|
||||
<i id="print-button" class="fa fa-print"></i>
|
||||
</a>
|
||||
</div>
|
||||
</div>
|
||||
</div>
|
||||
|
||||
|
||||
<div id="search-wrapper" class="hidden">
|
||||
<form id="searchbar-outer" class="searchbar-outer">
|
||||
<input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
|
||||
</form>
|
||||
<div id="searchresults-outer" class="searchresults-outer hidden">
|
||||
<div id="searchresults-header" class="searchresults-header"></div>
|
||||
<ul id="searchresults">
|
||||
</ul>
|
||||
</div>
|
||||
</div>
|
||||
|
||||
|
||||
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
|
||||
<script type="text/javascript">
|
||||
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
|
||||
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
|
||||
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
|
||||
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
|
||||
});
|
||||
</script>
|
||||
|
||||
<div id="content" class="content">
|
||||
<main>
|
||||
<a class="header" href="#hello2" id="hello2"><h1>hello2</h1></a>
|
||||
<p>Okay so let's have a look again:</p>
|
||||
<p><code>hello1</code></p>
|
||||
<pre><pre class="playpen"><code class="language-rust">#![feature(start)]
|
||||
#![no_std]
|
||||
|
||||
#[cfg(not(test))]
|
||||
#[panic_handler]
|
||||
fn panic(_info: &core::panic::PanicInfo) -> ! {
|
||||
loop {}
|
||||
}
|
||||
|
||||
#[start]
|
||||
fn main(_argc: isize, _argv: *const *const u8) -> isize {
|
||||
unsafe {
|
||||
(0x04000000 as *mut u16).write_volatile(0x0403);
|
||||
(0x06000000 as *mut u16).offset(120 + 80 * 240).write_volatile(0x001F);
|
||||
(0x06000000 as *mut u16).offset(136 + 80 * 240).write_volatile(0x03E0);
|
||||
(0x06000000 as *mut u16).offset(120 + 96 * 240).write_volatile(0x7C00);
|
||||
loop {}
|
||||
}
|
||||
}
|
||||
</code></pre></pre>
|
||||
<p>Now let's clean this up so that it's clearer what's going on.</p>
|
||||
<p>First we'll label that display control stuff:</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub const DISPCNT: *mut u16 = 0x04000000 as *mut u16;
|
||||
pub const MODE3: u16 = 3;
|
||||
pub const BG2: u16 = 0b100_0000_0000;
|
||||
#}</code></pre></pre>
|
||||
<p>Next we make some const values for the actual pixel drawing</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub const VRAM: usize = 0x06000000;
|
||||
pub const SCREEN_WIDTH: isize = 240;
|
||||
#}</code></pre></pre>
|
||||
<p>And then we want a small helper function for putting together a color value.</p>
|
||||
<p>Happily, this one can even be declared as a const function. At the time of
|
||||
writing, we've got the "minimal const fn" support in nightly. It really is quite
|
||||
limited, but I'm happy to let rustc and LLVM pre-compute as much as they can
|
||||
when it comes to the GBA's tiny CPU.</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
|
||||
blue << 10 | green << 5 | red
|
||||
}
|
||||
#}</code></pre></pre>
|
||||
<p>Finally, we'll make a function for drawing a pixel in Mode 3. Even though it's
|
||||
just a one-liner, having the "important parts" be labeled as function arguments
|
||||
usually helps you think about it a lot better.</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
|
||||
(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write_volatile(color);
|
||||
}
|
||||
#}</code></pre></pre>
|
||||
<p>So now we've got this:</p>
|
||||
<p><code>hello2</code></p>
|
||||
<pre><pre class="playpen"><code class="language-rust">#![feature(start)]
|
||||
#![no_std]
|
||||
|
||||
#[cfg(not(test))]
|
||||
#[panic_handler]
|
||||
fn panic(_info: &core::panic::PanicInfo) -> ! {
|
||||
loop {}
|
||||
}
|
||||
|
||||
#[start]
|
||||
fn main(_argc: isize, _argv: *const *const u8) -> isize {
|
||||
unsafe {
|
||||
DISPCNT.write_volatile(MODE3 | BG2);
|
||||
mode3_pixel(120, 80, rgb16(31, 0, 0));
|
||||
mode3_pixel(136, 80, rgb16(0, 31, 0));
|
||||
mode3_pixel(120, 96, rgb16(0, 0, 31));
|
||||
loop {}
|
||||
}
|
||||
}
|
||||
|
||||
pub const DISPCNT: *mut u16 = 0x04000000 as *mut u16;
|
||||
pub const MODE3: u16 = 3;
|
||||
pub const BG2: u16 = 0b100_0000_0000;
|
||||
|
||||
pub const VRAM: usize = 0x06000000;
|
||||
pub const SCREEN_WIDTH: isize = 240;
|
||||
|
||||
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
|
||||
blue << 10 | green << 5 | red
|
||||
}
|
||||
|
||||
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
|
||||
(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write_volatile(color);
|
||||
}
|
||||
</code></pre></pre>
|
||||
|
||||
</main>
|
||||
|
||||
<nav class="nav-wrapper" aria-label="Page navigation">
|
||||
<!-- Mobile navigation buttons -->
|
||||
|
||||
<a rel="prev" href="../ch1/video_memory_intro.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
||||
<i class="fa fa-angle-left"></i>
|
||||
</a>
|
||||
|
||||
|
||||
|
||||
|
||||
<div style="clear: both"></div>
|
||||
</nav>
|
||||
</div>
|
||||
</div>
|
||||
|
||||
<nav class="nav-wide-wrapper" aria-label="Page navigation">
|
||||
|
||||
<a href="../ch1/video_memory_intro.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
||||
<i class="fa fa-angle-left"></i>
|
||||
</a>
|
||||
|
||||
|
||||
|
||||
</nav>
|
||||
|
||||
</div>
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
<script src="../elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
|
||||
<script src="../mark.min.js" type="text/javascript" charset="utf-8"></script>
|
||||
<script src="../searcher.js" type="text/javascript" charset="utf-8"></script>
|
||||
|
||||
|
||||
<script src="../clipboard.min.js" type="text/javascript" charset="utf-8"></script>
|
||||
<script src="../highlight.js" type="text/javascript" charset="utf-8"></script>
|
||||
<script src="../book.js" type="text/javascript" charset="utf-8"></script>
|
||||
|
||||
<!-- Custom JS scripts -->
|
||||
|
||||
|
||||
|
||||
|
||||
</body>
|
||||
</html>
|
||||
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html" class="active"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html" class="active"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="../ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
|
|||
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html" class="active"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html" class="active"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="../ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
|
|||
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html" class="active"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html" class="active"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="../ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
@ -157,9 +157,10 @@ own demos and chapters later on, so that's all we'll say about them for now.</p>
|
|||
<p>Modes 3, 4, and 5 are "Bitmap" modes. These let you write individual pixels to
|
||||
locations on the screen.</p>
|
||||
<ul>
|
||||
<li><strong>Mode 3</strong> is full resolution (240w x 160h) RBG15 color. You might not be used to
|
||||
RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
|
||||
bits for each color channel, and the highest bit is totally ignored.</li>
|
||||
<li><strong>Mode 3</strong> is full resolution (240w x 160h) RBG15 color. You might not be used
|
||||
to RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
|
||||
bits for each color channel stored within a <code>u16</code> value, and the highest bit is
|
||||
simply ignored.</li>
|
||||
<li><strong>Mode 4</strong> is full resolution paletted color. Instead of being a <code>u16</code> color, each
|
||||
pixel value is a <code>u8</code> palette index entry, and then the display uses the
|
||||
palette memory (which we'll talk about later) to store the actual color data.
|
||||
|
|
@ -172,9 +173,10 @@ reduced resolution to compensate (video memory is only so big!). The screen is
|
|||
effectively only 160w x 128h in this mode.</li>
|
||||
</ul>
|
||||
<a class="header" href="#cgb-mode" id="cgb-mode"><h2>CGB Mode</h2></a>
|
||||
<p>Bit 3 is read only. It's on if you're running in CGB mode. Since we're making
|
||||
GBA games you'd think that it'll never be on at all, but I guess you can change
|
||||
it with BIOS stuff. Still, basically not an important bit.</p>
|
||||
<p>Bit 3 is effectively read only. Technically it can be flipped using a BIOS call,
|
||||
but when you write to the display control normally it won't write to this bit,
|
||||
so we'll call it effectively read only.</p>
|
||||
<p>This bit is on if the CPU is in CGB mode.</p>
|
||||
<a class="header" href="#page-flipping" id="page-flipping"><h2>Page Flipping</h2></a>
|
||||
<p>Bit 4 lets you pick which page to use. This is only relevent in video modes 4 or
|
||||
5, and is just ignored otherwise. It's very easy to remember: when the bit is 0
|
||||
|
|
@ -213,6 +215,8 @@ some nifty graphical effects.</p>
|
|||
binary</a>, and we get
|
||||
<code>0b100_0000_0011</code>. So, that's setting Mode 3 with background 2 enabled and
|
||||
nothing else special.</p>
|
||||
<p>However, I think we can do better than that. This is a prime target for more
|
||||
newtyping as we attempt a <code>hello2</code> program.</p>
|
||||
|
||||
</main>
|
||||
|
||||
|
|
|
|||
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html" class="active"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="../ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="../ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="../ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="../ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="../ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="../ch1/video_memory_intro.html" class="active"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="../ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
@ -151,15 +151,88 @@ trying to set an individual byte, and we also have to be careful if we use
|
|||
<code>memcopy</code> or <code>memset</code> as well, because they're byte oriented by default and
|
||||
don't know to follow the special rules.</p>
|
||||
<a class="header" href="#rgb15" id="rgb15"><h2>RGB15</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>As I said before, RGB15 stores a color within a <code>u16</code> value using 5 bits for
|
||||
each color channel.</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub const RED: u16 = 0b0_00000_00000_11111;
|
||||
pub const GREEN: u16 = 0b0_00000_11111_00000;
|
||||
pub const BLUE: u16 = 0b0_11111_00000_00000;
|
||||
#}</code></pre></pre>
|
||||
<p>In Mode 3 and Mode 5 we write direct color values into VRAM, and in Mode 4 we
|
||||
write palette index values, and then the color values go into the PALRAM.</p>
|
||||
<a class="header" href="#mode-3" id="mode-3"><h2>Mode 3</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>Mode 3 is pretty easy. We have a full resolution grid of rgb15 pixels. There's
|
||||
160 rows of 240 pixels each, with the base address being the top left corner. A
|
||||
particular pixel uses normal "2d indexing" math:</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
let row_five_col_seven = 5 + (7 * SCREEN_WIDTH);
|
||||
#}</code></pre></pre>
|
||||
<p>To draw a pixel, we just write a value at the address for the row and col that
|
||||
we want to draw to.</p>
|
||||
<a class="header" href="#mode-4" id="mode-4"><h2>Mode 4</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>Mode 4 introduces page flipping. Instead of one giant page at <code>0x0600_0000</code>,
|
||||
there's Page 0 at <code>0x0600_0000</code> and then Page 1 at <code>0x0600_A000</code>. The resolution
|
||||
for each page is the same as above, but instead of writing <code>u16</code> values, the
|
||||
memory is treated as <code>u8</code> indexes into PALRAM. The PALRAM starts at
|
||||
<code>0x0500_0000</code>, and there's enough space for 256 palette entries (each a <code>u16</code>).</p>
|
||||
<p>To set the color of a palette entry we just do a normal <code>u16</code> write_volatile.</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
(0x0500_0000 as *mut u16).offset(target_index).write_volatile(new_color)
|
||||
#}</code></pre></pre>
|
||||
<p>To draw a pixel we set the palette entry that we want the pixel to use. However,
|
||||
we must remember the "minimum size" write limitation that applies to VRAM. So,
|
||||
if we want to change just a single pixel at a time we must</p>
|
||||
<ol>
|
||||
<li>Read the full <code>u16</code> it's a part of.</li>
|
||||
<li>Clear the half of the <code>u16</code> we're going to replace</li>
|
||||
<li>Write the half of the <code>u16</code> we're going to replace with the new value</li>
|
||||
<li>Write that result back to the address.</li>
|
||||
</ol>
|
||||
<p>So, the math for finding a byte offset is the same as Mode 3 (since they're both
|
||||
a 2d grid). If the byte offset is EVEN it'll be the high bits of the <code>u16</code> at
|
||||
half the byte offset rounded down. If the offset is ODD it'll be the low bits of
|
||||
the <code>u16</code> at half the byte.</p>
|
||||
<p>Does that make sense?</p>
|
||||
<ul>
|
||||
<li>If we want to write pixel (0,0) the byte offset is 0, so we change the high
|
||||
bits of <code>u16</code> offset 0. Then we want to write to (1,0), so the byte offset is
|
||||
1, so we change the low bits of <code>u16</code> offset 0. The pixels are next to each
|
||||
other, and the target bytes are next to each other, good so far.</li>
|
||||
<li>If we want to write to (5,6) that'd be byte <code>5 + 6 * 240 = 1445</code>, so we'd
|
||||
target the low bits of <code>u16</code> offset <code>floor(1445/2) = 722</code>.</li>
|
||||
</ul>
|
||||
<p>As you can see, trying to write individual pixels in Mode 4 is mostly a bad
|
||||
time. Fret not! We don't <em>have</em> to write individual bytes. If our data is
|
||||
arranged correctly ahead of time we can just write <code>u16</code> or <code>u32</code> values
|
||||
directly. The video hardware doesn't care, it'll get along just fine.</p>
|
||||
<a class="header" href="#mode-5" id="mode-5"><h2>Mode 5</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>Mode 5 is also a two page mode, but instead of compressing the size of a pixel's
|
||||
data to fit in two pages, we compress the resolution.</p>
|
||||
<p>Mode 5 is full <code>u16</code> color, but only 160w x 128h per page.</p>
|
||||
<a class="header" href="#in-conclusion" id="in-conclusion"><h2>In Conclusion...</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>So what got written into VRAM in <code>hello1</code>?</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
(0x06000000 as *mut u16).offset(120 + 80 * 240).write_volatile(0x001F);
|
||||
(0x06000000 as *mut u16).offset(136 + 80 * 240).write_volatile(0x03E0);
|
||||
(0x06000000 as *mut u16).offset(120 + 96 * 240).write_volatile(0x7C00);
|
||||
#}</code></pre></pre>
|
||||
<p>So at pixels <code>(120,80)</code>, <code>(136,80)</code>, and <code>(120,96)</code> we write three values. Once
|
||||
again we probably need to <a href="https://www.wolframalpha.com/">convert them</a> into
|
||||
binary to make sense of it.</p>
|
||||
<ul>
|
||||
<li>0x001F: 0b11111</li>
|
||||
<li>0x03E0: 0b11111_00000</li>
|
||||
<li>0x7C00: 0b11111_00000_00000</li>
|
||||
</ul>
|
||||
<p>Ah, of course, a red pixel, a green pixel, and a blue pixel.</p>
|
||||
|
||||
</main>
|
||||
|
||||
|
|
@ -172,6 +245,10 @@ don't know to follow the special rules.</p>
|
|||
|
||||
|
||||
|
||||
<a rel="next" href="../ch1/hello2.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
||||
<i class="fa fa-angle-right"></i>
|
||||
</a>
|
||||
|
||||
|
||||
<div style="clear: both"></div>
|
||||
</nav>
|
||||
|
|
@ -186,6 +263,10 @@ don't know to follow the special rules.</p>
|
|||
|
||||
|
||||
|
||||
<a href="../ch1/hello2.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
||||
<i class="fa fa-angle-right"></i>
|
||||
</a>
|
||||
|
||||
</nav>
|
||||
|
||||
</div>
|
||||
|
|
|
|||
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
|
|||
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="introduction.html" class="active"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="introduction.html" class="active"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
|
|||
217
docs/print.html
217
docs/print.html
|
|
@ -72,7 +72,7 @@
|
|||
</script>
|
||||
|
||||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||||
<ol class="chapter"><li><a href="introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li></ol></li></ol>
|
||||
<ol class="chapter"><li><a href="introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><a href="ch0/index.html"><strong aria-hidden="true">2.</strong> Ch 0: Development Setup</a></li><li><a href="ch1/index.html"><strong aria-hidden="true">3.</strong> Ch 1: Hello GBA</a></li><li><ol class="section"><li><a href="ch1/hello1.html"><strong aria-hidden="true">3.1.</strong> hello1</a></li><li><a href="ch1/io_registers.html"><strong aria-hidden="true">3.2.</strong> IO Registers</a></li><li><a href="ch1/the_display_control.html"><strong aria-hidden="true">3.3.</strong> The Display Control</a></li><li><a href="ch1/video_memory_intro.html"><strong aria-hidden="true">3.4.</strong> Video Memory Intro</a></li><li><a href="ch1/hello2.html"><strong aria-hidden="true">3.5.</strong> hello2</a></li></ol></li></ol>
|
||||
</nav>
|
||||
|
||||
<div id="page-wrapper" class="page-wrapper">
|
||||
|
|
@ -181,8 +181,12 @@ cargo will figure it all out for you.</p>
|
|||
You can find them in the root of the <a href="https://github.com/rust-console/gba">rust-console/gba
|
||||
repo</a>.</p>
|
||||
<ul>
|
||||
<li><code>thumbv4-nintendo-agb.json</code> describes the overall GBA to cargo-xbuild so it knows
|
||||
what to do.</li>
|
||||
<li><code>thumbv4-none-agb.json</code> describes the overall GBA to cargo-xbuild so it knows
|
||||
what to do. This is actually a somewhat made up target name since there's no
|
||||
official target name. The GBA is essentially the same as a normal
|
||||
<code>thumbv4-none-eabi</code> device, but we give it the "agb" signifier so that later
|
||||
on we'll be able to use rust's <code>cfg</code> ability to allow our code to know if it's
|
||||
specifically targeting a GBA or some other similar device (like an NDS).</li>
|
||||
<li><code>crt0.s</code> describes some ASM startup stuff. If you have more ASM to place here
|
||||
later on this is where you can put it. You also need to build it into a
|
||||
<code>crt0.o</code> file before it can actually be used, but we'll cover that below.</li>
|
||||
|
|
@ -202,7 +206,7 @@ practically instant operation.</li>
|
|||
</ul>
|
||||
</li>
|
||||
<li>
|
||||
<p><code>cargo xbuild --target thumbv4-nintendo-agb.json</code></p>
|
||||
<p><code>cargo xbuild --target thumbv4-none-agb.json</code></p>
|
||||
<ul>
|
||||
<li>This builds your Rust source. It accepts <em>most of</em> the normal options, such
|
||||
as <code>--release</code>, and options, such as <code>--bin foo</code> or <code>--examples</code>, that you'd
|
||||
|
|
@ -231,7 +235,7 @@ emulators can also do it.</p>
|
|||
transfer to a flash cart there's a little more to do.</p>
|
||||
<ul>
|
||||
<li>
|
||||
<p><code>arm-none-eabi-objcopy -O binary target/thumbv4-nintendo-agb/MODE/BIN_NAME target/ROM_NAME.gba</code></p>
|
||||
<p><code>arm-none-eabi-objcopy -O binary target/thumbv4-none-agb/MODE/BIN_NAME target/ROM_NAME.gba</code></p>
|
||||
<ul>
|
||||
<li>This will perform an <a href="https://linux.die.net/man/1/objcopy">objcopy</a> on our
|
||||
program. Here I've named the program <code>arm-none-eabi-objcopy</code>, which is what
|
||||
|
|
@ -247,7 +251,7 @@ bare memory dump of the program.</li>
|
|||
<code>cargo doc</code> and stuff it gets kinda crowded, so it goes like this:
|
||||
<ul>
|
||||
<li>Since our program was built for a non-local target, first we've got a
|
||||
directory named for that target, <code>thumbv4-nintendo-agb/</code></li>
|
||||
directory named for that target, <code>thumbv4-none-agb/</code></li>
|
||||
<li>Next, the "MODE" is either <code>debug/</code> or <code>release/</code>, depending on if we had
|
||||
the <code>--release</code> flag included. You'll probably only be packing release
|
||||
mode programs all the way into GBA roms, but it works with either mode.</li>
|
||||
|
|
@ -443,6 +447,10 @@ write to <code>d</code> will <em>always</em> happen after the write to <code>c</
|
|||
volatile doesn't make things thread-safe, you still need atomic for that.
|
||||
However, the GBA doesn't have threads, so we don't have to worry about thread
|
||||
safety concerns.</p>
|
||||
<p>Accordingly, our first bit of code for our library will be a <em>newtype</em> over a
|
||||
normal <code>*mut T</code> so that it has volatile reads and writes as the default. We'll
|
||||
cover the details later on when we try writing a <code>hello2</code> program, once we know
|
||||
more of what's going on.</p>
|
||||
<a class="header" href="#io-registers" id="io-registers"><h1>IO Registers</h1></a>
|
||||
<p>The GBA has a large number of <strong>IO Registers</strong> (not to be confused with CPU
|
||||
registers). These are special memory locations from <code>0x04000000</code> to
|
||||
|
|
@ -498,9 +506,10 @@ own demos and chapters later on, so that's all we'll say about them for now.</p>
|
|||
<p>Modes 3, 4, and 5 are "Bitmap" modes. These let you write individual pixels to
|
||||
locations on the screen.</p>
|
||||
<ul>
|
||||
<li><strong>Mode 3</strong> is full resolution (240w x 160h) RBG15 color. You might not be used to
|
||||
RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
|
||||
bits for each color channel, and the highest bit is totally ignored.</li>
|
||||
<li><strong>Mode 3</strong> is full resolution (240w x 160h) RBG15 color. You might not be used
|
||||
to RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
|
||||
bits for each color channel stored within a <code>u16</code> value, and the highest bit is
|
||||
simply ignored.</li>
|
||||
<li><strong>Mode 4</strong> is full resolution paletted color. Instead of being a <code>u16</code> color, each
|
||||
pixel value is a <code>u8</code> palette index entry, and then the display uses the
|
||||
palette memory (which we'll talk about later) to store the actual color data.
|
||||
|
|
@ -513,9 +522,10 @@ reduced resolution to compensate (video memory is only so big!). The screen is
|
|||
effectively only 160w x 128h in this mode.</li>
|
||||
</ul>
|
||||
<a class="header" href="#cgb-mode" id="cgb-mode"><h2>CGB Mode</h2></a>
|
||||
<p>Bit 3 is read only. It's on if you're running in CGB mode. Since we're making
|
||||
GBA games you'd think that it'll never be on at all, but I guess you can change
|
||||
it with BIOS stuff. Still, basically not an important bit.</p>
|
||||
<p>Bit 3 is effectively read only. Technically it can be flipped using a BIOS call,
|
||||
but when you write to the display control normally it won't write to this bit,
|
||||
so we'll call it effectively read only.</p>
|
||||
<p>This bit is on if the CPU is in CGB mode.</p>
|
||||
<a class="header" href="#page-flipping" id="page-flipping"><h2>Page Flipping</h2></a>
|
||||
<p>Bit 4 lets you pick which page to use. This is only relevent in video modes 4 or
|
||||
5, and is just ignored otherwise. It's very easy to remember: when the bit is 0
|
||||
|
|
@ -554,6 +564,8 @@ some nifty graphical effects.</p>
|
|||
binary</a>, and we get
|
||||
<code>0b100_0000_0011</code>. So, that's setting Mode 3 with background 2 enabled and
|
||||
nothing else special.</p>
|
||||
<p>However, I think we can do better than that. This is a prime target for more
|
||||
newtyping as we attempt a <code>hello2</code> program.</p>
|
||||
<a class="header" href="#video-memory-intro" id="video-memory-intro"><h1>Video Memory Intro</h1></a>
|
||||
<p>The GBA's Video RAM is 96k stretching from <code>0x0600_0000</code> to <code>0x0601_7FFF</code>.</p>
|
||||
<p>The Video RAM can only be accessed totally freely during a Vertical Blank
|
||||
|
|
@ -569,15 +581,186 @@ trying to set an individual byte, and we also have to be careful if we use
|
|||
<code>memcopy</code> or <code>memset</code> as well, because they're byte oriented by default and
|
||||
don't know to follow the special rules.</p>
|
||||
<a class="header" href="#rgb15" id="rgb15"><h2>RGB15</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>As I said before, RGB15 stores a color within a <code>u16</code> value using 5 bits for
|
||||
each color channel.</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub const RED: u16 = 0b0_00000_00000_11111;
|
||||
pub const GREEN: u16 = 0b0_00000_11111_00000;
|
||||
pub const BLUE: u16 = 0b0_11111_00000_00000;
|
||||
#}</code></pre></pre>
|
||||
<p>In Mode 3 and Mode 5 we write direct color values into VRAM, and in Mode 4 we
|
||||
write palette index values, and then the color values go into the PALRAM.</p>
|
||||
<a class="header" href="#mode-3" id="mode-3"><h2>Mode 3</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>Mode 3 is pretty easy. We have a full resolution grid of rgb15 pixels. There's
|
||||
160 rows of 240 pixels each, with the base address being the top left corner. A
|
||||
particular pixel uses normal "2d indexing" math:</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
let row_five_col_seven = 5 + (7 * SCREEN_WIDTH);
|
||||
#}</code></pre></pre>
|
||||
<p>To draw a pixel, we just write a value at the address for the row and col that
|
||||
we want to draw to.</p>
|
||||
<a class="header" href="#mode-4" id="mode-4"><h2>Mode 4</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>Mode 4 introduces page flipping. Instead of one giant page at <code>0x0600_0000</code>,
|
||||
there's Page 0 at <code>0x0600_0000</code> and then Page 1 at <code>0x0600_A000</code>. The resolution
|
||||
for each page is the same as above, but instead of writing <code>u16</code> values, the
|
||||
memory is treated as <code>u8</code> indexes into PALRAM. The PALRAM starts at
|
||||
<code>0x0500_0000</code>, and there's enough space for 256 palette entries (each a <code>u16</code>).</p>
|
||||
<p>To set the color of a palette entry we just do a normal <code>u16</code> write_volatile.</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
(0x0500_0000 as *mut u16).offset(target_index).write_volatile(new_color)
|
||||
#}</code></pre></pre>
|
||||
<p>To draw a pixel we set the palette entry that we want the pixel to use. However,
|
||||
we must remember the "minimum size" write limitation that applies to VRAM. So,
|
||||
if we want to change just a single pixel at a time we must</p>
|
||||
<ol>
|
||||
<li>Read the full <code>u16</code> it's a part of.</li>
|
||||
<li>Clear the half of the <code>u16</code> we're going to replace</li>
|
||||
<li>Write the half of the <code>u16</code> we're going to replace with the new value</li>
|
||||
<li>Write that result back to the address.</li>
|
||||
</ol>
|
||||
<p>So, the math for finding a byte offset is the same as Mode 3 (since they're both
|
||||
a 2d grid). If the byte offset is EVEN it'll be the high bits of the <code>u16</code> at
|
||||
half the byte offset rounded down. If the offset is ODD it'll be the low bits of
|
||||
the <code>u16</code> at half the byte.</p>
|
||||
<p>Does that make sense?</p>
|
||||
<ul>
|
||||
<li>If we want to write pixel (0,0) the byte offset is 0, so we change the high
|
||||
bits of <code>u16</code> offset 0. Then we want to write to (1,0), so the byte offset is
|
||||
1, so we change the low bits of <code>u16</code> offset 0. The pixels are next to each
|
||||
other, and the target bytes are next to each other, good so far.</li>
|
||||
<li>If we want to write to (5,6) that'd be byte <code>5 + 6 * 240 = 1445</code>, so we'd
|
||||
target the low bits of <code>u16</code> offset <code>floor(1445/2) = 722</code>.</li>
|
||||
</ul>
|
||||
<p>As you can see, trying to write individual pixels in Mode 4 is mostly a bad
|
||||
time. Fret not! We don't <em>have</em> to write individual bytes. If our data is
|
||||
arranged correctly ahead of time we can just write <code>u16</code> or <code>u32</code> values
|
||||
directly. The video hardware doesn't care, it'll get along just fine.</p>
|
||||
<a class="header" href="#mode-5" id="mode-5"><h2>Mode 5</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>Mode 5 is also a two page mode, but instead of compressing the size of a pixel's
|
||||
data to fit in two pages, we compress the resolution.</p>
|
||||
<p>Mode 5 is full <code>u16</code> color, but only 160w x 128h per page.</p>
|
||||
<a class="header" href="#in-conclusion-1" id="in-conclusion-1"><h2>In Conclusion...</h2></a>
|
||||
<p>TODO</p>
|
||||
<p>So what got written into VRAM in <code>hello1</code>?</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
(0x06000000 as *mut u16).offset(120 + 80 * 240).write_volatile(0x001F);
|
||||
(0x06000000 as *mut u16).offset(136 + 80 * 240).write_volatile(0x03E0);
|
||||
(0x06000000 as *mut u16).offset(120 + 96 * 240).write_volatile(0x7C00);
|
||||
#}</code></pre></pre>
|
||||
<p>So at pixels <code>(120,80)</code>, <code>(136,80)</code>, and <code>(120,96)</code> we write three values. Once
|
||||
again we probably need to <a href="https://www.wolframalpha.com/">convert them</a> into
|
||||
binary to make sense of it.</p>
|
||||
<ul>
|
||||
<li>0x001F: 0b11111</li>
|
||||
<li>0x03E0: 0b11111_00000</li>
|
||||
<li>0x7C00: 0b11111_00000_00000</li>
|
||||
</ul>
|
||||
<p>Ah, of course, a red pixel, a green pixel, and a blue pixel.</p>
|
||||
<a class="header" href="#hello2" id="hello2"><h1>hello2</h1></a>
|
||||
<p>Okay so let's have a look again:</p>
|
||||
<p><code>hello1</code></p>
|
||||
<pre><pre class="playpen"><code class="language-rust">#![feature(start)]
|
||||
#![no_std]
|
||||
|
||||
#[cfg(not(test))]
|
||||
#[panic_handler]
|
||||
fn panic(_info: &core::panic::PanicInfo) -> ! {
|
||||
loop {}
|
||||
}
|
||||
|
||||
#[start]
|
||||
fn main(_argc: isize, _argv: *const *const u8) -> isize {
|
||||
unsafe {
|
||||
(0x04000000 as *mut u16).write_volatile(0x0403);
|
||||
(0x06000000 as *mut u16).offset(120 + 80 * 240).write_volatile(0x001F);
|
||||
(0x06000000 as *mut u16).offset(136 + 80 * 240).write_volatile(0x03E0);
|
||||
(0x06000000 as *mut u16).offset(120 + 96 * 240).write_volatile(0x7C00);
|
||||
loop {}
|
||||
}
|
||||
}
|
||||
</code></pre></pre>
|
||||
<p>Now let's clean this up so that it's clearer what's going on.</p>
|
||||
<p>First we'll label that display control stuff:</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub const DISPCNT: *mut u16 = 0x04000000 as *mut u16;
|
||||
pub const MODE3: u16 = 3;
|
||||
pub const BG2: u16 = 0b100_0000_0000;
|
||||
#}</code></pre></pre>
|
||||
<p>Next we make some const values for the actual pixel drawing</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub const VRAM: usize = 0x06000000;
|
||||
pub const SCREEN_WIDTH: isize = 240;
|
||||
#}</code></pre></pre>
|
||||
<p>And then we want a small helper function for putting together a color value.</p>
|
||||
<p>Happily, this one can even be declared as a const function. At the time of
|
||||
writing, we've got the "minimal const fn" support in nightly. It really is quite
|
||||
limited, but I'm happy to let rustc and LLVM pre-compute as much as they can
|
||||
when it comes to the GBA's tiny CPU.</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
|
||||
blue << 10 | green << 5 | red
|
||||
}
|
||||
#}</code></pre></pre>
|
||||
<p>Finally, we'll make a function for drawing a pixel in Mode 3. Even though it's
|
||||
just a one-liner, having the "important parts" be labeled as function arguments
|
||||
usually helps you think about it a lot better.</p>
|
||||
<pre><pre class="playpen"><code class="language-rust">
|
||||
# #![allow(unused_variables)]
|
||||
#fn main() {
|
||||
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
|
||||
(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write_volatile(color);
|
||||
}
|
||||
#}</code></pre></pre>
|
||||
<p>So now we've got this:</p>
|
||||
<p><code>hello2</code></p>
|
||||
<pre><pre class="playpen"><code class="language-rust">#![feature(start)]
|
||||
#![no_std]
|
||||
|
||||
#[cfg(not(test))]
|
||||
#[panic_handler]
|
||||
fn panic(_info: &core::panic::PanicInfo) -> ! {
|
||||
loop {}
|
||||
}
|
||||
|
||||
#[start]
|
||||
fn main(_argc: isize, _argv: *const *const u8) -> isize {
|
||||
unsafe {
|
||||
DISPCNT.write_volatile(MODE3 | BG2);
|
||||
mode3_pixel(120, 80, rgb16(31, 0, 0));
|
||||
mode3_pixel(136, 80, rgb16(0, 31, 0));
|
||||
mode3_pixel(120, 96, rgb16(0, 0, 31));
|
||||
loop {}
|
||||
}
|
||||
}
|
||||
|
||||
pub const DISPCNT: *mut u16 = 0x04000000 as *mut u16;
|
||||
pub const MODE3: u16 = 3;
|
||||
pub const BG2: u16 = 0b100_0000_0000;
|
||||
|
||||
pub const VRAM: usize = 0x06000000;
|
||||
pub const SCREEN_WIDTH: isize = 240;
|
||||
|
||||
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
|
||||
blue << 10 | green << 5 | red
|
||||
}
|
||||
|
||||
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
|
||||
(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write_volatile(color);
|
||||
}
|
||||
</code></pre></pre>
|
||||
|
||||
</main>
|
||||
|
||||
|
|
|
|||
File diff suppressed because one or more lines are too long
File diff suppressed because one or more lines are too long
34
examples/hello2.rs
Normal file
34
examples/hello2.rs
Normal file
|
|
@ -0,0 +1,34 @@
|
|||
#![feature(start)]
|
||||
#![no_std]
|
||||
|
||||
#[cfg(not(test))]
|
||||
#[panic_handler]
|
||||
fn panic(_info: &core::panic::PanicInfo) -> ! {
|
||||
loop {}
|
||||
}
|
||||
|
||||
#[start]
|
||||
fn main(_argc: isize, _argv: *const *const u8) -> isize {
|
||||
unsafe {
|
||||
DISPCNT.write_volatile(MODE3 | BG2);
|
||||
mode3_pixel(120, 80, rgb16(31, 0, 0));
|
||||
mode3_pixel(136, 80, rgb16(0, 31, 0));
|
||||
mode3_pixel(120, 96, rgb16(0, 0, 31));
|
||||
loop {}
|
||||
}
|
||||
}
|
||||
|
||||
pub const DISPCNT: *mut u16 = 0x04000000 as *mut u16;
|
||||
pub const MODE3: u16 = 3;
|
||||
pub const BG2: u16 = 0b100_0000_0000;
|
||||
|
||||
pub const VRAM: usize = 0x06000000;
|
||||
pub const SCREEN_WIDTH: isize = 240;
|
||||
|
||||
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
|
||||
blue << 10 | green << 5 | red
|
||||
}
|
||||
|
||||
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
|
||||
(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write_volatile(color);
|
||||
}
|
||||
|
|
@ -1,13 +1,13 @@
|
|||
//! Things that I wish were in core, but aren't.
|
||||
|
||||
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
|
||||
#[repr(transparent)]
|
||||
/// A simple wrapper to any `*mut T` so that the basic "read" and "write"
|
||||
/// operations are volatile.
|
||||
///
|
||||
/// Accessing the GBA's IO registers and video ram and specific other places on
|
||||
/// **must** be done with volatile operations. Having this wrapper makes that
|
||||
/// more clear for all the global const values into IO registers.
|
||||
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
|
||||
#[repr(transparent)]
|
||||
pub struct VolatilePtr<T>(pub *mut T);
|
||||
|
||||
impl<T> core::fmt::Pointer for VolatilePtr<T> {
|
||||
|
|
|
|||
|
|
@ -28,5 +28,5 @@ pub mod video_ram;
|
|||
|
||||
/// Combines the Red, Blue, and Green provided into a single color value.
|
||||
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
|
||||
red | green << 5 | blue << 10
|
||||
blue << 10 | green << 5 | red
|
||||
}
|
||||
|
|
|
|||
|
|
@ -28,6 +28,13 @@ pub const SCREEN_HEIGHT: isize = 160;
|
|||
/// value as just being a `usize`.
|
||||
pub const VRAM_BASE_ADDRESS: usize = 0x0600_0000;
|
||||
|
||||
/// Draws a pixel to the screen while in Display Mode 3, with bounds checks.
|
||||
pub fn mode3_pixel(col: isize, row: isize, color: u16) {
|
||||
assert!(col >= 0 && col < SCREEN_WIDTH);
|
||||
assert!(row >= 0 && row < SCREEN_HEIGHT);
|
||||
unsafe { mode3_pixel_unchecked(col, row, color) }
|
||||
}
|
||||
|
||||
/// Draws a pixel to the screen while in Display Mode 3.
|
||||
///
|
||||
/// Coordinates are relative to the top left corner.
|
||||
|
|
@ -39,13 +46,6 @@ pub const VRAM_BASE_ADDRESS: usize = 0x0600_0000;
|
|||
///
|
||||
/// * `col` must be in `0..SCREEN_WIDTH`
|
||||
/// * `row` must be in `0..SCREEN_HEIGHT`
|
||||
pub unsafe fn mode3_plot_unchecked(col: isize, row: isize, color: u16) {
|
||||
pub unsafe fn mode3_pixel_unchecked(col: isize, row: isize, color: u16) {
|
||||
core::ptr::write_volatile((VRAM_BASE_ADDRESS as *mut u16).offset(col + row * SCREEN_WIDTH), color);
|
||||
}
|
||||
|
||||
/// Draws a pixel to the screen while in Display Mode 3, with bounds checks.
|
||||
pub fn mode3_plot(col: isize, row: isize, color: u16) {
|
||||
assert!(col >= 0 && col < SCREEN_WIDTH);
|
||||
assert!(row >= 0 && row < SCREEN_HEIGHT);
|
||||
unsafe { mode3_plot_unchecked(col, row, color) }
|
||||
}
|
||||
|
|
|
|||
|
|
@ -18,7 +18,7 @@
|
|||
"linker": "arm-none-eabi-ld",
|
||||
"linker-flavor": "ld",
|
||||
"linker-is-gnu": true,
|
||||
"llvm-target": "thumbv4-nintendo-agb",
|
||||
"llvm-target": "thumbv4-none-agb",
|
||||
"os": "none",
|
||||
"panic-strategy": "abort",
|
||||
"pre-link-args": {
|
||||
Loading…
Reference in a new issue