From dcd4e6384e3fab32809d01738ecd84011b4f0cc7 Mon Sep 17 00:00:00 2001
From: eZio Pan <eziopan@qq.com>
Date: Sat, 23 Dec 2023 19:45:56 +0800
Subject: [PATCH] enable output compare preload for TIM

keep output waveform integrity
---
 examples/stm32f4/src/bin/ws2812_pwm_dma.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/examples/stm32f4/src/bin/ws2812_pwm_dma.rs b/examples/stm32f4/src/bin/ws2812_pwm_dma.rs
index c4181d024..cdce36f2e 100644
--- a/examples/stm32f4/src/bin/ws2812_pwm_dma.rs
+++ b/examples/stm32f4/src/bin/ws2812_pwm_dma.rs
@@ -21,6 +21,7 @@
 use embassy_executor::Spawner;
 use embassy_stm32::gpio::OutputType;
 use embassy_stm32::pac;
+use embassy_stm32::pac::timer::vals::Ocpe;
 use embassy_stm32::time::khz;
 use embassy_stm32::timer::simple_pwm::{PwmPin, SimplePwm};
 use embassy_stm32::timer::{Channel, CountingMode};
@@ -89,6 +90,12 @@ 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, Ocpe::ENABLED));
+
     // make sure PWM output keep low on first start
     ws2812_pwm.set_duty(pwm_channel, 0);