1 files changed, 153 insertions, 0 deletions

diff --git a/examples/stm32f7/src/bin/pwm_ringbuffer.rs b/examples/stm32f7/src/bin/pwm_ringbuffer.rs
new file mode 100644
index 000000000..4d191ac13
--- /dev/null
+++ b/examples/stm32f7/src/bin/pwm_ringbuffer.rs
@@ -0,0 +1,153 @@
+#![no_std]
+#![no_main]
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::Config;
+use embassy_stm32::gpio::OutputType;
+use embassy_stm32::time::mhz;
+use embassy_stm32::timer::simple_pwm::{PwmPin, SimplePwm};
+use embassy_time::Timer;
+use {defmt_rtt as _, panic_probe as _};
+
+// If you are trying this and your USB device doesn't connect, the most
+// common issues are the RCC config and vbus_detection
+//
+// See https://embassy.dev/book/#_the_usb_examples_are_not_working_on_my_board_is_there_anything_else_i_need_to_configure
+// for more information.
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    info!("PWM Ring Buffer Example");
+
+    let mut config = Config::default();
+    {
+        use embassy_stm32::rcc::*;
+        use embassy_stm32::time::Hertz;
+        config.rcc.hse = Some(Hse {
+            freq: Hertz(8_000_000),
+            mode: HseMode::Bypass,
+        });
+        config.rcc.pll_src = PllSource::HSE;
+        config.rcc.pll = Some(Pll {
+            prediv: PllPreDiv::DIV4,
+            mul: PllMul::MUL200,
+            divp: Some(PllPDiv::DIV2), // 8mhz / 4 * 200 / 2 = 200Mhz
+            divq: Some(PllQDiv::DIV4), // 8mhz / 4 * 200 / 4 = 100Mhz
+            divr: None,
+        });
+        config.rcc.ahb_pre = AHBPrescaler::DIV1;
+        config.rcc.apb1_pre = APBPrescaler::DIV4;
+        config.rcc.apb2_pre = APBPrescaler::DIV2;
+        config.rcc.sys = Sysclk::PLL1_P;
+    }
+    let p = embassy_stm32::init(config);
+
+    // Initialize PWM on TIM1
+    let ch1_pin = PwmPin::new(p.PE9, OutputType::PushPull);
+    let ch2_pin = PwmPin::new(p.PE11, OutputType::PushPull);
+    let mut pwm = SimplePwm::new(
+        p.TIM1,
+        Some(ch1_pin),
+        Some(ch2_pin),
+        None,
+        None,
+        mhz(1),
+        Default::default(),
+    );
+
+    // Use channel 1 for static PWM at 50%
+    let mut ch1 = pwm.ch1();
+    ch1.enable();
+    ch1.set_duty_cycle_fraction(1, 2);
+    info!("Channel 1 (PE9/D6): Static 50% duty cycle");
+
+    // Get max duty from channel 1 before converting channel 2
+    let max_duty = ch1.max_duty_cycle();
+    info!("PWM max duty: {}", max_duty);
+
+    // Create a DMA ring buffer for channel 2
+    const BUFFER_SIZE: usize = 128;
+    static mut DMA_BUFFER: [u16; BUFFER_SIZE] = [0u16; BUFFER_SIZE];
+    let dma_buffer = unsafe { &mut *core::ptr::addr_of_mut!(DMA_BUFFER) };
+
+    // Pre-fill buffer with initial sine wave using lookup table approach
+    for i in 0..BUFFER_SIZE {
+        // Simple sine approximation using triangle wave
+        let phase = (i * 256) / BUFFER_SIZE;
+        let sine_approx = if phase < 128 {
+            phase as u16 * 2
+        } else {
+            (255 - phase) as u16 * 2
+        };
+        dma_buffer[i] = (sine_approx as u32 * max_duty as u32 / 256) as u16;
+    }
+
+    // Convert channel 2 to ring-buffered PWM
+    let mut ring_pwm = pwm.ch1().into_ring_buffered_channel(p.DMA2_CH5, dma_buffer);
+
+    info!("Ring buffer capacity: {}", ring_pwm.capacity());
+
+    // Pre-write some initial data to the buffer before starting
+    info!("Pre-writing initial waveform data...");
+
+    ring_pwm.write(&[0; BUFFER_SIZE]).unwrap();
+
+    // Enable the PWM channel output
+    ring_pwm.enable();
+
+    // Start the DMA ring buffer
+    ring_pwm.start();
+    info!("Channel 2 (PE11/D5): Ring buffered sine wave started");
+
+    // Give DMA time to start consuming
+    Timer::after_millis(10).await;
+
+    // Continuously update the waveform
+    let mut phase: f32 = 0.0;
+    let mut amplitude: f32 = 1.0;
+    let mut amplitude_direction = -0.05;
+
+    loop {
+        // Generate new waveform data with varying amplitude
+        let mut new_data = [0u16; 32];
+        for i in 0..new_data.len() {
+            // Triangle wave approximation for sine
+            let pos = ((i as u32 + phase as u32) * 4) % 256;
+            let sine_approx = if pos < 128 {
+                pos as u16 * 2
+            } else {
+                (255 - pos) as u16 * 2
+            };
+            let scaled = (sine_approx as u32 * (amplitude * 256.0) as u32) / (256 * 256);
+            new_data[i] = ((scaled * max_duty as u32) / 256) as u16;
+        }
+
+        // Write new data to the ring buffer
+        match ring_pwm.write_exact(&new_data).await {
+            Ok(_remaining) => {}
+            Err(e) => {
+                info!("Write error: {:?}", e);
+            }
+        }
+
+        // Update phase for animation effect
+        phase += 2.0;
+        if phase >= 64.0 {
+            phase = 0.0;
+        }
+
+        // Vary amplitude for breathing effect
+        amplitude += amplitude_direction;
+        if amplitude <= 0.2 || amplitude >= 1.0 {
+            amplitude_direction = -amplitude_direction;
+        }
+
+        // Log buffer status periodically
+        if (phase as u32) % 10 == 0 {
+            match ring_pwm.len() {
+                Ok(len) => info!("Ring buffer fill: {}/{}", len, ring_pwm.capacity()),
+                Err(_) => info!("Error reading buffer length"),
+            }
+        }
+    }
+}