RP2040 Simple DMA Example

basic-dma.rs

#![no_std]
#![no_main]

/**
* Basic RP2040 DMA example, just copying one value in memory to another place in memory using DMA
*/
use bsp::entry;
use cortex_m::singleton;
use defmt::*;
use defmt_rtt as _;
use panic_probe as _;

use rp_pico as bsp;

use bsp::hal::{clocks::init_clocks_and_plls, pac, watchdog::Watchdog};

#[entry]
fn main() -> ! {
    info!("Program start");

    let src: &'static mut u8 = singleton!(: u8 = 42).unwrap();
    let dest: &'static mut u8 = singleton!(: u8 = 0).unwrap();

    let mut pac = pac::Peripherals::take().unwrap();
    let mut watchdog = Watchdog::new(pac.WATCHDOG);

    // External high-speed crystal on the pico board is 12Mhz
    let external_xtal_freq_hz = 12_000_000u32;
    let _clocks = init_clocks_and_plls(
        external_xtal_freq_hz,
        pac.XOSC,
        pac.CLOCKS,
        pac.PLL_SYS,
        pac.PLL_USB,
        &mut pac.RESETS,
        &mut watchdog,
    )
    .ok()
    .unwrap();

    // Enable DMA peripheral
    pac.RESETS.reset.modify(|_, w| w.dma().clear_bit());
    while pac.RESETS.reset_done.read().dma().bit_is_clear() {}

    info!("RESETTING DMA");

    pac.DMA.chan_abort.write(|w| unsafe { w.bits(1) });
    while pac.DMA.chan_abort.read().bits() != 0 {}

    info!("DMA RESET");

    // Set DMA source address
    pac.DMA.ch[0]
        .ch_read_addr
        .modify(|_, w| unsafe { w.bits(src as *const u8 as u32) });

    // Set DMA destination address
    pac.DMA.ch[0]
        .ch_write_addr
        .modify(|_, w| unsafe { w.bits(dest as *const u8 as u32) });

    // Set DMA transfer count (just 1)
    pac.DMA.ch[0]
        .ch_trans_count
        .modify(|_, w| unsafe { w.bits(1) });

    // Configure and start DMA channel 0
    pac.DMA.ch[0].ch_ctrl_trig.modify(|_, w| unsafe {
        w
            // Set unpaced timer
            .treq_sel()
            .bits(0x3f)
            // Set data size to 0x0 (8 bit)
            .data_size()
            .bits(0x0)
            // Chain to itself (do not chain)
            .chain_to()
            .bits(0)
            // Enable channel 0
            .en()
            .bit(true)
    });

    // Wait for DMA transfer to be done
    while pac.DMA.ch[0].ch_ctrl_trig.read().busy().bit_is_set() {}

    // This should now be the value of src
    info!("DEST VALUE: {}", dest);

    loop {
        cortex_m::asm::nop();
    }
}