Add a simple example for PIO.

rp2040-hal/examples/pio_blink.rs

@@ -0,0 +1,65 @@
+//! Blinks the LED on a Pico board, using a PIO program
+//!
+//! This will blink an LED attached to GP25, which is the pin the Pico uses for the on-board LED.
+#![no_std]
+#![no_main]
+
+use cortex_m_rt::entry;
+use hal::gpio::{FunctionPio0, Pin};
+use hal::pac;
+use hal::sio::Sio;
+use panic_halt as _;
+use rp2040_hal as hal;
+
+#[link_section = ".boot2"]
+#[used]
+pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER;
+
+#[entry]
+fn main() -> ! {
+    let mut pac = pac::Peripherals::take().unwrap();
+
+    let sio = Sio::new(pac.SIO);
+    let pins = hal::gpio::Pins::new(
+        pac.IO_BANK0,
+        pac.PADS_BANK0,
+        sio.gpio_bank0,
+        &mut pac.RESETS,
+    );
+
+    // configure LED pin for Pio0.
+    let _led: Pin<_, FunctionPio0> = pins.gpio25.into_mode();
+    // PIN id for use inside of PIO
+    let led_pin_id = 25;
+
+    // Define some simple PIO program.
+    const MAX_DELAY: u8 = 31;
+    let mut a = pio::Assembler::<32>::new();
+    let mut wrap_target = a.label();
+    let mut wrap_source = a.label();
+    // Set pin as Out
+    a.set(pio::SetDestination::PINDIRS, 1);
+    a.bind(&mut wrap_target);
+    // Set pin low
+    a.set_with_delay(pio::SetDestination::PINS, 0, MAX_DELAY);
+    // Set pin high
+    a.set_with_delay(pio::SetDestination::PINS, 1, MAX_DELAY);
+    // NOP
+    a.bind(&mut wrap_source);
+    let program = a.assemble_with_wrap(wrap_source, wrap_target);
+
+    // Initialize and start PIO
+    let pio = rp2040_hal::pio::PIO::new(pac.PIO0, &mut pac.RESETS);
+    let sm = &pio.state_machines()[0];
+    let div = 0f32; // as slow as possible (0 is interpreted as 65536)
+    rp2040_hal::pio::PIOBuilder::default()
+        .with_program(&program)
+        .set_pins(led_pin_id, 1)
+        .clock_divisor(div)
+        .build(&pio, sm)
+        .unwrap();
+
+    // PIO runs in background, independently from CPU
+    #[allow(clippy::empty_loop)]
+    loop {}
+}