Update blinky example.

rp2040-hal/examples/blinky.rs

@@ -1,38 +1,95 @@
-//! Blinks the LED on a Pico board
+//! # GPIO 'Blinky' Example
 //!
-//! This will blink an LED attached to GP25, which is the pin the Pico uses for the on-board LED.
+//! This application demonstrates how to control a GPIO pin on the RP2040.
+//!
+//! 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;
-use embedded_hal::digital::v2::OutputPin;
+
-use hal::pac;
+// Ensure we halt the program on panic (if we don't mention this crate it won't
-use hal::sio::Sio;
+// 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;
+
+// A GPIO trait we need
+use embedded_hal::digital::v2::OutputPin;
+
+// 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]
 pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER;
 
+/// 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;
+
+/// Run RP2040 at 125 MHz
+const SYS_FREQ_HZ: u32 = hal::pll::common_configs::PLL_SYS_125MHZ.vco_freq.0;
+
+/// 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 toggles a GPIO pin in
+/// an infinite loop. If there is an LED connected to that pin, it will blink.
 #[entry]
 fn main() -> ! {
+    // Grab our singleton objects
     let mut pac = pac::Peripherals::take().unwrap();
+    let core = pac::CorePeripherals::take().unwrap();
 
-    let sio = Sio::new(pac.SIO);
+    // 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();
+
+    let mut delay = cortex_m::delay::Delay::new(core.SYST, SYS_FREQ_HZ);
+
+    // 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 led_pin = pins.gpio25.into_push_pull_output();
 
+    // Configure GPIO25 as an output
+    let mut led_pin = pins.gpio25.into_push_pull_output();
     loop {
         led_pin.set_high().unwrap();
         // TODO: Replace with proper 1s delays once we have clocks working
-        cortex_m::asm::delay(500_000);
+        delay.delay_ms(500);
         led_pin.set_low().unwrap();
-        cortex_m::asm::delay(500_000);
+        delay.delay_ms(500);
     }
 }
+
+// End of file