我正试图使用DMA从存储的缓冲区中更改每个周期的PWM占空比。这与这个主题非常接近，但代码现在有点过时了。我还在我的项目中使用stm32l4xx_hal实现。
我现在要做的是：
// 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
);
}
我可以直接用set_duty设置占空比，它可以工作，但DMA不会进行传输。
我混淆了PWM和DMA外围设备的通道，对于任何感兴趣的人来说，这里有一个适用于我的主循环：
#[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 {
}
}