implement PWM waveform generating with DMA

embassy-stm32/build.rs

@@ -1008,6 +1008,7 @@ fn main() {
         (("quadspi", "QUADSPI"), quote!(crate::qspi::QuadDma)),
         (("dac", "CH1"), quote!(crate::dac::DacDma1)),
         (("dac", "CH2"), quote!(crate::dac::DacDma2)),
+        (("timer", "UP"), quote!(crate::timer::UpDma)),
     ]
     .into();
 
@@ -1023,6 +1024,16 @@ fn main() {
                 }
 
                 if let Some(tr) = signals.get(&(regs.kind, ch.signal)) {
+                    // TIM6 of stm32f334 is special, DMA channel for TIM6 depending on SYSCFG state
+                    if chip_name.starts_with("stm32f334") && p.name == "TIM6" {
+                        continue;
+                    }
+
+                    // TIM6 of stm32f378 is special, DMA channel for TIM6 depending on SYSCFG state
+                    if chip_name.starts_with("stm32f378") && p.name == "TIM6" {
+                        continue;
+                    }
+
                     let peri = format_ident!("{}", p.name);
 
                     let channel = if let Some(channel) = &ch.channel {

embassy-stm32/src/timer/mod.rs

@@ -91,7 +91,12 @@ pub(crate) mod sealed {
 
         /// Enable/disable the update interrupt.
         fn enable_update_interrupt(&mut self, enable: bool) {
-            Self::regs().dier().write(|r| r.set_uie(enable));
+            Self::regs().dier().modify(|r| r.set_uie(enable));
+        }
+
+        /// Enable/disable the update dma.
+        fn enable_update_dma(&mut self, enable: bool) {
+            Self::regs().dier().modify(|r| r.set_ude(enable));
         }
 
         /// Enable/disable autoreload preload.
@@ -288,6 +293,14 @@ pub(crate) mod sealed {
         fn get_compare_value(&self, channel: Channel) -> u16 {
             Self::regs_gp16().ccr(channel.index()).read().ccr()
         }
+
+        /// Set output compare preload.
+        fn set_output_compare_preload(&mut self, channel: Channel, preload: bool) {
+            let channel_index = channel.index();
+            Self::regs_gp16()
+                .ccmr_output(channel_index / 2)
+                .modify(|w| w.set_ocpe(channel_index % 2, preload));
+        }
     }
 
     /// Capture/Compare 16-bit timer instance with complementary pin support.
@@ -676,3 +689,6 @@ foreach_interrupt! {
         }
     };
 }
+
+// Update Event trigger DMA for every timer
+dma_trait!(UpDma, Basic16bitInstance);

embassy-stm32/src/timer/simple_pwm.rs

@@ -55,11 +55,12 @@ channel_impl!(new_ch3, Ch3, Channel3Pin);
 channel_impl!(new_ch4, Ch4, Channel4Pin);
 
 /// Simple PWM driver.
-pub struct SimplePwm<'d, T> {
+pub struct SimplePwm<'d, T, Dma> {
     inner: PeripheralRef<'d, T>,
+    dma: PeripheralRef<'d, Dma>,
 }
 
-impl<'d, T: CaptureCompare16bitInstance> SimplePwm<'d, T> {
+impl<'d, T: CaptureCompare16bitInstance, Dma> SimplePwm<'d, T, Dma> {
     /// Create a new simple PWM driver.
     pub fn new(
         tim: impl Peripheral<P = T> + 'd,
@@ -69,16 +70,22 @@ impl<'d, T: CaptureCompare16bitInstance> SimplePwm<'d, T> {
         _ch4: Option<PwmPin<'d, T, Ch4>>,
         freq: Hertz,
         counting_mode: CountingMode,
+        dma: impl Peripheral<P = Dma> + 'd,
     ) -> Self {
-        Self::new_inner(tim, freq, counting_mode)
+        Self::new_inner(tim, freq, counting_mode, dma)
     }
 
-    fn new_inner(tim: impl Peripheral<P = T> + 'd, freq: Hertz, counting_mode: CountingMode) -> Self {
+    fn new_inner(
-        into_ref!(tim);
+        tim: impl Peripheral<P = T> + 'd,
+        freq: Hertz,
+        counting_mode: CountingMode,
+        dma: impl Peripheral<P = Dma> + 'd,
+    ) -> Self {
+        into_ref!(tim, dma);
 
         T::enable_and_reset();
 
-        let mut this = Self { inner: tim };
+        let mut this = Self { inner: tim, dma };
 
         this.inner.set_counting_mode(counting_mode);
         this.set_frequency(freq);
@@ -86,14 +93,13 @@ impl<'d, T: CaptureCompare16bitInstance> SimplePwm<'d, T> {
 
         this.inner.enable_outputs();
 
-        this.inner
+        [Channel::Ch1, Channel::Ch2, Channel::Ch3, Channel::Ch4]
-            .set_output_compare_mode(Channel::Ch1, OutputCompareMode::PwmMode1);
+            .iter()
-        this.inner
+            .for_each(|&channel| {
-            .set_output_compare_mode(Channel::Ch2, OutputCompareMode::PwmMode1);
+                this.inner.set_output_compare_mode(channel, OutputCompareMode::PwmMode1);
-        this.inner
+                this.inner.set_output_compare_preload(channel, true)
-            .set_output_compare_mode(Channel::Ch3, OutputCompareMode::PwmMode1);
+            });
-        this.inner
+
-            .set_output_compare_mode(Channel::Ch4, OutputCompareMode::PwmMode1);
         this
     }
 
@@ -141,7 +147,71 @@ impl<'d, T: CaptureCompare16bitInstance> SimplePwm<'d, T> {
     }
 }
 
-impl<'d, T: CaptureCompare16bitInstance> embedded_hal_02::Pwm for SimplePwm<'d, T> {
+impl<'d, T: CaptureCompare16bitInstance + Basic16bitInstance, Dma> SimplePwm<'d, T, Dma>
+where
+    Dma: super::UpDma<T>,
+{
+    /// Generate a sequence of PWM waveform
+    pub async fn gen_waveform(&mut self, channel: Channel, duty: &[u16]) {
+        duty.iter().all(|v| v.le(&self.get_max_duty()));
+
+        self.inner.enable_update_dma(true);
+
+        #[cfg_attr(any(stm32f334, stm32f378), allow(clippy::let_unit_value))]
+        let req = self.dma.request();
+
+        self.enable(channel);
+
+        #[cfg(not(any(bdma, gpdma)))]
+        let dma_regs = self.dma.regs();
+        #[cfg(not(any(bdma, gpdma)))]
+        let isr_num = self.dma.num() / 4;
+        #[cfg(not(any(bdma, gpdma)))]
+        let isr_bit = self.dma.num() % 4;
+
+        #[cfg(not(any(bdma, gpdma)))]
+        // clean DMA FIFO error before a transfer
+        if dma_regs.isr(isr_num).read().feif(isr_bit) {
+            dma_regs.ifcr(isr_num).write(|v| v.set_feif(isr_bit, true));
+        }
+
+        unsafe {
+            #[cfg(not(any(bdma, gpdma)))]
+            use crate::dma::{Burst, FifoThreshold};
+            use crate::dma::{Transfer, TransferOptions};
+
+            let dma_transfer_option = TransferOptions {
+                #[cfg(not(any(bdma, gpdma)))]
+                fifo_threshold: Some(FifoThreshold::Full),
+                #[cfg(not(any(bdma, gpdma)))]
+                mburst: Burst::Incr8,
+                ..Default::default()
+            };
+
+            Transfer::new_write(
+                &mut self.dma,
+                req,
+                duty,
+                T::regs_gp16().ccr(channel.index()).as_ptr() as *mut _,
+                dma_transfer_option,
+            )
+            .await
+        };
+
+        self.disable(channel);
+
+        self.inner.enable_update_dma(false);
+
+        #[cfg(not(any(bdma, gpdma)))]
+        // Since DMA is closed before timer update event trigger DMA is turn off, it will almost always trigger a DMA FIFO error.
+        // Thus, we will always clean DMA FEIF after each transfer
+        if dma_regs.isr(isr_num).read().feif(isr_bit) {
+            dma_regs.ifcr(isr_num).write(|v| v.set_feif(isr_bit, true));
+        }
+    }
+}
+
+impl<'d, T: CaptureCompare16bitInstance, Dma> embedded_hal_02::Pwm for SimplePwm<'d, T, Dma> {
     type Channel = Channel;
     type Time = Hertz;
     type Duty = u16;

examples/stm32f4/src/bin/pwm.rs

@@ -3,6 +3,7 @@
 
 use defmt::*;
 use embassy_executor::Spawner;
+use embassy_stm32::dma;
 use embassy_stm32::gpio::OutputType;
 use embassy_stm32::time::khz;
 use embassy_stm32::timer::simple_pwm::{PwmPin, SimplePwm};
@@ -16,7 +17,16 @@ async fn main(_spawner: Spawner) {
     info!("Hello World!");
 
     let ch1 = PwmPin::new_ch1(p.PE9, OutputType::PushPull);
-    let mut pwm = SimplePwm::new(p.TIM1, Some(ch1), None, None, None, khz(10), Default::default());
+    let mut pwm = SimplePwm::new(
+        p.TIM1,
+        Some(ch1),
+        None,
+        None,
+        None,
+        khz(10),
+        Default::default(),
+        dma::NoDma,
+    );
     let max = pwm.get_max_duty();
     pwm.enable(Channel::Ch1);
 

examples/stm32f4/src/bin/ws2812_pwm.rs

@@ -2,15 +2,9 @@
 // We assume the DIN pin of ws2812 connect to GPIO PB4, and ws2812 is properly powered.
 //
 // The idea is that the data rate of ws2812 is 800 kHz, and it use different duty ratio to represent bit 0 and bit 1.
-// Thus we can set TIM overflow at 800 kHz, and let TIM Update Event trigger a DMA transfer, then let DMA change CCR value,
+// Thus we can set TIM overflow at 800 kHz, and change duty ratio of TIM to meet the bit representation of ws2812.
-// such that pwm duty ratio meet the bit representation of ws2812.
 //
-// You may want to modify TIM CCR with Cortex core directly,
+// you may also want to take a look at `ws2812_spi.rs` file, which make use of SPI instead.
-// but according to my test, Cortex core will need to run far more than 100 MHz to catch up with TIM.
-// Thus we need to use a DMA.
-//
-// This demo is a combination of HAL, PAC, and manually invoke `dma::Transfer`.
-// If you need a simpler way to control ws2812, you may want to take a look at `ws2812_spi.rs` file, which make use of SPI.
 //
 // Warning:
 // DO NOT stare at ws2812 directy (especially after each MCU Reset), its (max) brightness could easily make your eyes feel burn.
@@ -20,7 +14,6 @@
 
 use embassy_executor::Spawner;
 use embassy_stm32::gpio::OutputType;
-use embassy_stm32::pac;
 use embassy_stm32::time::khz;
 use embassy_stm32::timer::simple_pwm::{PwmPin, SimplePwm};
 use embassy_stm32::timer::{Channel, CountingMode};
@@ -52,7 +45,7 @@ async fn main(_spawner: Spawner) {
         device_config.rcc.sys = Sysclk::PLL1_P;
     }
 
-    let mut dp = embassy_stm32::init(device_config);
+    let dp = embassy_stm32::init(device_config);
 
     let mut ws2812_pwm = SimplePwm::new(
         dp.TIM3,
@@ -62,6 +55,7 @@ async fn main(_spawner: Spawner) {
         None,
         khz(800), // data rate of ws2812
         CountingMode::EdgeAlignedUp,
+        dp.DMA1_CH2,
     );
 
     // construct ws2812 non-return-to-zero (NRZ) code bit by bit
@@ -89,62 +83,19 @@ async fn main(_spawner: Spawner) {
 
     let pwm_channel = Channel::Ch1;
 
-    // PAC level hacking, enable output compare preload
-    // keep output waveform integrity
-    pac::TIM3
-        .ccmr_output(pwm_channel.index())
-        .modify(|v| v.set_ocpe(0, true));
-
     // make sure PWM output keep low on first start
     ws2812_pwm.set_duty(pwm_channel, 0);
 
-    {
-        use embassy_stm32::dma::{Burst, FifoThreshold, Transfer, TransferOptions};
-
-        // configure FIFO and MBURST of DMA, to minimize DMA occupation on AHB/APB
-        let mut dma_transfer_option = TransferOptions::default();
-        dma_transfer_option.fifo_threshold = Some(FifoThreshold::Full);
-        dma_transfer_option.mburst = Burst::Incr8;
-
     // flip color at 2 Hz
     let mut ticker = Ticker::every(Duration::from_millis(500));
 
     loop {
         for &color in color_list {
-                // start PWM output
+            ws2812_pwm.gen_waveform(Channel::Ch1, color).await;
-                ws2812_pwm.enable(pwm_channel);
-
-                // PAC level hacking, enable timer-update-event trigger DMA
-                pac::TIM3.dier().modify(|v| v.set_ude(true));
-
-                unsafe {
-                    Transfer::new_write(
-                        // with &mut, we can easily reuse same DMA channel multiple times
-                        &mut dp.DMA1_CH2,
-                        5,
-                        color,
-                        pac::TIM3.ccr(pwm_channel.index()).as_ptr() as *mut _,
-                        dma_transfer_option,
-                    )
-                    .await;
-
-                    // Turn off timer-update-event trigger DMA as soon as possible.
-                    // Then clean the FIFO Error Flag if set.
-                    pac::TIM3.dier().modify(|v| v.set_ude(false));
-                    if pac::DMA1.isr(0).read().feif(2) {
-                        pac::DMA1.ifcr(0).write(|v| v.set_feif(2, true));
-                    }
-
             // ws2812 need at least 50 us low level input to confirm the input data and change it's state
             Timer::after_micros(50).await;
-                }
-
-                // stop PWM output for saving some energy
-                ws2812_pwm.disable(pwm_channel);
-
             // wait until ticker tick
             ticker.next().await;
         }
     }
 }
-}

examples/stm32g4/src/bin/pwm.rs

@@ -3,6 +3,7 @@
 
 use defmt::*;
 use embassy_executor::Spawner;
+use embassy_stm32::dma;
 use embassy_stm32::gpio::OutputType;
 use embassy_stm32::time::khz;
 use embassy_stm32::timer::simple_pwm::{PwmPin, SimplePwm};
@@ -16,7 +17,16 @@ async fn main(_spawner: Spawner) {
     info!("Hello World!");
 
     let ch1 = PwmPin::new_ch1(p.PC0, OutputType::PushPull);
-    let mut pwm = SimplePwm::new(p.TIM1, Some(ch1), None, None, None, khz(10), Default::default());
+    let mut pwm = SimplePwm::new(
+        p.TIM1,
+        Some(ch1),
+        None,
+        None,
+        None,
+        khz(10),
+        Default::default(),
+        dma::NoDma,
+    );
     let max = pwm.get_max_duty();
     pwm.enable(Channel::Ch1);
 

examples/stm32h7/src/bin/pwm.rs

@@ -7,7 +7,7 @@ use embassy_stm32::gpio::OutputType;
 use embassy_stm32::time::khz;
 use embassy_stm32::timer::simple_pwm::{PwmPin, SimplePwm};
 use embassy_stm32::timer::Channel;
-use embassy_stm32::Config;
+use embassy_stm32::{dma, Config};
 use embassy_time::Timer;
 use {defmt_rtt as _, panic_probe as _};
 
@@ -38,7 +38,16 @@ async fn main(_spawner: Spawner) {
     info!("Hello World!");
 
     let ch1 = PwmPin::new_ch1(p.PA6, OutputType::PushPull);
-    let mut pwm = SimplePwm::new(p.TIM3, Some(ch1), None, None, None, khz(10), Default::default());
+    let mut pwm = SimplePwm::new(
+        p.TIM3,
+        Some(ch1),
+        None,
+        None,
+        None,
+        khz(10),
+        Default::default(),
+        dma::NoDma,
+    );
     let max = pwm.get_max_duty();
     pwm.enable(Channel::Ch1);