如何使用 Rust 让 DMA 改变 PWM 端口的占空比？

Question

我正在尝试使用 DMA 从存储的缓冲区更改每个周期的 PWM 占空比。它与此 topic 非常接近，但代码现在有点过时了。我也在为我的项目使用 stm32l4xx_hal 实现。

我现在有的是：

// setup the PWM
let mut gpioa = dp.GPIOA.split(&mut rcc.ahb2);
let c1 = gpioa.pa0.into_push_pull_output(&mut gpioa.moder, &mut gpioa.otyper).into_af1(&mut gpioa.moder, &mut gpioa.afrl);
let mut pwm = dp.TIM2.pwm(c1, 1.hz(), clocks, &mut rcc.apb1r1);
let max = pwm.get_max_duty();

// general variables
let buffer: [u32; 10] = [ 0, max, 0, max, 0, max / 8, max / 4, max / 2, max, 0 ];

pwm.set_duty(0);
pwm.enable();

let tim2;
unsafe {
    tim2 = &*TIM2::ptr(); // general timer 2 pointer
    let dma1 = &*DMA1::ptr(); // DMA 1 pointer
    
    rcc_ptr.ahb1enr.modify(|_, w| w.dma1en().set_bit()); // enable DMA1 clock: peripheral clock enable register

    // timer for DMA configuration
    tim2.dier.modify(|_, w| w.tde().set_bit()); // enable DMA trigger
    tim2.dier.modify(|_, w| w.cc1de().set_bit()); // enable capture/compare 1 DMA request
    tim2.dier.modify(|_, w| w.ude().set_bit()); // enable update DMA request
    tim2.dier.modify(|_, w| w.uie().set_bit()); // enable update interrupt enable

    // DMA configuration
    dma1.cmar5.write(|w| w.ma().bits(buffer.as_ptr() as u32)); // write the buffer to the memory adress
    dma1.cndtr5.write(|w| w.ndt().bits(buffer.len() as u16)); // number of data to transfer register
    dma1.cselr.write(|w| w.c1s().bits(4)); // set CxS[3:0] to 0100 to map the DMA request to timer 2 channel 1
    dma1.cpar5.write(|w| w.pa().bits(0x4000_0034)); // set the DMA peripheral address register to the capture/compare 1 of TIM2
    dma1.ccr5.modify(|_, w| w
        .mem2mem().clear_bit() // memory-to-memory disabled
        .pl().high() // set highest priority
        .msize().bits(2) // size in memory of each transfer: b10 = 32 bits long
        .psize().bits(2) // size of peripheral: b10 = 32 bits long
        .minc().set_bit() // memory increment mode enabled
        .pinc().clear_bit() // peripheral increment mode disabled
        .circ().set_bit() // circular mode: the dma transfer is repeated automatically when finished
        .dir().set_bit() // data transfer direction: 1 = read from memory
        .teie().set_bit() // transfer error interrupt enabled
        .htie().set_bit() // half transfer interrupt enabled
        .tcie().set_bit() // transfer complete interrupt enabled
        .en().set_bit() // channel enable
    );
}

我可以直接使用 set_duty 设置占空比并且它可以工作，但是 DMA 没有发生传输。

Answer 1

我混淆了 PWM 和 DMA 外围设备的通道，对于任何感兴趣的人，这里是一个适合我的主循环：

#[entry]
fn main() -> ! {
    // setup the board
    let dp = stm32l4xx_hal::stm32::Peripherals::take().unwrap();

    // setup the peripherals
    let mut flash = dp.FLASH.constrain();
    let mut rcc = dp.RCC.constrain();
    let clocks = rcc.cfgr.freeze(&mut flash.acr); // sets by default the clock to 16mhz ?!
    let _channels = dp.DMA1.split(&mut rcc.ahb1);

    // setup the PWM
    let mut gpioa = dp.GPIOA.split(&mut rcc.ahb2);
    let c1 = gpioa.pa0.into_push_pull_output(&mut gpioa.moder, &mut gpioa.otyper).into_af1(&mut gpioa.moder, &mut gpioa.afrl);
    let mut pwm = dp.TIM2.pwm(c1, 800.khz(), clocks, &mut rcc.apb1r1);
    let max = pwm.get_max_duty();

    let one_duty = (max * 90 / 125) as u32;
    let zero_duty = (max * 35 / 125) as u32;
    let buffer: [u32; 122] = [
        one_duty, one_duty, one_duty, one_duty, one_duty, one_duty, one_duty, one_duty,
        zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty,
        zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty,

        zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty,
        zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty,
        one_duty, one_duty, one_duty, one_duty, one_duty, one_duty, one_duty, one_duty,

        zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty,
        one_duty, one_duty, one_duty, one_duty, one_duty, one_duty, one_duty, one_duty,
        zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty, zero_duty,

        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    ];

    pwm.set_duty(0);
    pwm.enable();

    unsafe {
        let tim2 = &*TIM2::ptr(); // general timer 2 pointer
        let rcc_ptr = &*RCC::ptr(); // RCC pointer
        let dma1 = &*DMA1::ptr(); // DMA 1 pointer
    
        rcc_ptr.ahb1enr.modify(|_, w| w.dma1en().set_bit()); // enable DMA1 clock: peripheral clock enable register

        // timer for DMA configuration
        tim2.dier.write(|w| w.tde().set_bit()); // enable DMA trigger
        tim2.dier.write(|w| w.ude().set_bit()); // enable update DMA request

        let _a = &tim2.ccr1 as *const _ as u32; // very different from 0x4000_0034

        // DMA configuration
        dma1.cselr.write(|w| w.c2s().bits(0b0100)); // set CxS[3:0] to 0100 to map the DMA request to timer 2 channel 1
        dma1.cpar2.write(|w| w.pa().bits(0x4000_0034)); // set the DMA peripheral address register to the capture/compare 1 of TIM2
        dma1.cmar2.write(|w| w.ma().bits(buffer.as_ptr() as u32)); // write the buffer to the memory adress
        dma1.cndtr2.write(|w| w.ndt().bits(buffer.len() as u16)); // number of data to transfer register    
        dma1.ccr2.modify(|_, w| w
            .mem2mem().clear_bit() // memory-to-memory disabled
            .pl().high() // set highest priority
            .msize().bits(2) // size in memory of each transfer: b10 = 32 bits long
            .psize().bits(2) // size of peripheral: b10 = 32 bits long --> 32 or 16 ?? 
            .minc().set_bit() // memory increment mode enabled
            .pinc().clear_bit() // peripheral increment mode disabled
            .circ().set_bit() // circular mode: the dma transfer is repeated automatically when finished
            .dir().set_bit() // data transfer direction: 1 = read from memory
            .teie().set_bit() // transfer error interrupt enabled
            .htie().set_bit() // half transfer interrupt enabled
            .tcie().set_bit() // transfer complete interrupt enabled
            .en().set_bit() // channel enable
        );
    }

    loop {
    }
}

如何使用 Rust 让 DMA 改变 PWM 端口的占空比？

How to make DMA work for changing the duty cycle of a PWM port using Rust?

stm32

dma

rust

pwm