rp-hal-boards/rp2040-hal/examples/rom_funcs.rs

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//! # 'ROM Functions' Example
//!
//! This application demonstrates how to call functions in the RP2040's boot ROM.
//!
//! It may need to be adapted to your particular board layout and/or pin assignment.
//!
//! See the `Cargo.toml` file for Copyright and licence details.
#![no_std]
#![no_main]
// The macro for our start-up function
use cortex_m_rt::entry;
// Ensure we halt the program on panic (if we don't mention this crate it won't
// be linked)
use panic_halt as _;
// Alias for our HAL crate
use rp2040_hal as hal;
// A shorter alias for the Peripheral Access Crate, which provides low-level
// register access
use hal::pac;
// Some traits we need
use core::fmt::Write;
/// The linker will place this boot block at the start of our program image. We
// need this to help the ROM bootloader get our code up and running.
#[link_section = ".boot2"]
#[used]
2021-10-18 20:58:38 +11:00
pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_W25Q080;
/// External high-speed crystal on the Raspberry Pi Pico board is 12 MHz. Adjust
/// if your board has a different frequency
const XTAL_FREQ_HZ: u32 = 12_000_000u32;
/// Our Cortex-M systick goes from this value down to zero. For our timer maths
/// to work, this value must be of the form `2**N - 1`.
const SYSTICK_RELOAD: u32 = 0x00FF_FFFF;
/// Entry point to our bare-metal application.
///
/// The `#[entry]` macro ensures the Cortex-M start-up code calls this function
/// as soon as all global variables are initialised.
///
/// The function configures the RP2040 peripherals, then writes to the UART in
/// an inifinite loop.
#[entry]
fn main() -> ! {
// Grab our singleton objects
let mut pac = pac::Peripherals::take().unwrap();
let mut core = pac::CorePeripherals::take().unwrap();
// Set up the watchdog driver - needed by the clock setup code
let mut watchdog = hal::watchdog::Watchdog::new(pac.WATCHDOG);
// Configure the clocks
let clocks = hal::clocks::init_clocks_and_plls(
XTAL_FREQ_HZ,
pac.XOSC,
pac.CLOCKS,
pac.PLL_SYS,
pac.PLL_USB,
&mut pac.RESETS,
&mut watchdog,
)
.ok()
.unwrap();
// The single-cycle I/O block controls our GPIO pins
let sio = hal::sio::Sio::new(pac.SIO);
// Set the pins to their default state
let pins = hal::gpio::Pins::new(
pac.IO_BANK0,
pac.PADS_BANK0,
sio.gpio_bank0,
&mut pac.RESETS,
);
let mut uart = hal::uart::UartPeripheral::<_, _>::enable(
pac.UART0,
&mut pac.RESETS,
hal::uart::common_configs::_9600_8_N_1,
clocks.peripheral_clock.into(),
)
.unwrap();
// UART TX (characters sent from RP2040) on pin 1 (GPIO0)
let _tx_pin = pins.gpio0.into_mode::<hal::gpio::FunctionUart>();
// UART RX (characters reveived by RP2040) on pin 2 (GPIO1)
let _rx_pin = pins.gpio1.into_mode::<hal::gpio::FunctionUart>();
writeln!(uart, "ROM Copyright: {}", hal::rom_data::copyright_string()).unwrap();
writeln!(
uart,
"ROM Git Revision: 0x{:x}",
hal::rom_data::git_revision()
)
.unwrap();
// Some ROM functions are exported directly, so we can just call them
writeln!(
uart,
"popcount32(0xF000_0001) = {}",
hal::rom_data::popcount32(0xF000_0001)
)
.unwrap();
// Try to hide the numbers from the compiler so it is forced to do the maths
let x = hal::rom_data::popcount32(0xFF) as f32; // 8
let y = hal::rom_data::popcount32(0xFFF) as f32; // 12
// Use systick as a count-down timer
core.SYST.set_reload(SYSTICK_RELOAD);
core.SYST.clear_current();
core.SYST.enable_counter();
// Do some simple sums
let start_soft = cortex_m::peripheral::SYST::get_current();
core::sync::atomic::compiler_fence(core::sync::atomic::Ordering::SeqCst);
let soft_result = x * y;
core::sync::atomic::compiler_fence(core::sync::atomic::Ordering::SeqCst);
let end_soft = cortex_m::peripheral::SYST::get_current();
writeln!(
uart,
"{} x {} = {} in {} systicks (doing soft-float maths)",
x,
y,
soft_result,
calc_delta(start_soft, end_soft)
)
.unwrap();
// Some functions require a look-up in a table. First we do the lookup and
// find the function pointer in ROM (you only want to do this once per
// function).
let fmul = hal::rom_data::float_funcs::fmul();
// Then we can call the function whenever we want
let start_rom = cortex_m::peripheral::SYST::get_current();
let rom_result = fmul(x, y);
let end_rom = cortex_m::peripheral::SYST::get_current();
writeln!(
uart,
"{} x {} = {} in {} systicks (using the ROM)",
x,
y,
rom_result,
calc_delta(start_rom, end_rom)
)
.unwrap();
// Now just spin (whilst the UART does its thing)
for _ in 0..1_000_000 {
cortex_m::asm::nop();
}
// Reboot back into USB mode (no activity, both interfaces enabled)
rp2040_hal::rom_data::reset_to_usb_boot(0, 0);
// In case the reboot fails
loop {
cortex_m::asm::nop();
}
}
/// Calculate the number of systicks elapsed between two counter readings.
///
/// Note: SYSTICK starts at `SYSTICK_RELOAD` and counts down towards zero, so
/// these comparisons might appear to be backwards.
///
/// ```
/// assert_eq!(1, calc_delta(SYSTICK_RELOAD, SYSTICK_RELOAD - 1));
/// assert_eq!(2, calc_delta(0, SYSTICK_RELOAD - 1));
//// ```
fn calc_delta(start: u32, end: u32) -> u32 {
if start < end {
(start.wrapping_sub(end)) & SYSTICK_RELOAD
} else {
start - end
}
}
// End of file