103 lines
3.5 KiB
Rust
103 lines
3.5 KiB
Rust
// Configure TIM3 in PWM mode, and start DMA Transfer(s) to send color data into ws2812.
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// We assume the DIN pin of ws2812 connect to GPIO PB4, and ws2812 is properly powered.
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//
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// 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.
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// Thus we can set TIM overflow at 800 kHz, and change duty ratio of TIM to meet the bit representation of ws2812.
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//
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// you may also want to take a look at `ws2812_spi.rs` file, which make use of SPI instead.
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//
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// Warning:
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// DO NOT stare at ws2812 directy (especially after each MCU Reset), its (max) brightness could easily make your eyes feel burn.
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#![no_std]
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#![no_main]
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use embassy_executor::Spawner;
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use embassy_stm32::gpio::OutputType;
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use embassy_stm32::time::khz;
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use embassy_stm32::timer::low_level::CountingMode;
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use embassy_stm32::timer::simple_pwm::{PwmPin, SimplePwm};
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use embassy_stm32::timer::Channel;
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use embassy_time::{Duration, Ticker, Timer};
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use {defmt_rtt as _, panic_probe as _};
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#[embassy_executor::main]
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async fn main(_spawner: Spawner) {
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let mut device_config = embassy_stm32::Config::default();
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// set SYSCLK/HCLK/PCLK2 to 20 MHz, thus each tick is 0.05 us,
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// and ws2812 timings are integer multiples of 0.05 us
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{
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use embassy_stm32::rcc::*;
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use embassy_stm32::time::*;
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device_config.enable_debug_during_sleep = true;
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device_config.rcc.hse = Some(Hse {
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freq: mhz(12),
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mode: HseMode::Oscillator,
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});
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device_config.rcc.pll_src = PllSource::HSE;
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device_config.rcc.pll = Some(Pll {
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prediv: PllPreDiv::DIV6,
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mul: PllMul::MUL80,
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divp: Some(PllPDiv::DIV8),
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divq: None,
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divr: None,
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});
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device_config.rcc.sys = Sysclk::PLL1_P;
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}
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let mut dp = embassy_stm32::init(device_config);
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let mut ws2812_pwm = SimplePwm::new(
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dp.TIM3,
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Some(PwmPin::new_ch1(dp.PB4, OutputType::PushPull)),
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None,
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None,
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None,
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khz(800), // data rate of ws2812
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CountingMode::EdgeAlignedUp,
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);
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// construct ws2812 non-return-to-zero (NRZ) code bit by bit
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// ws2812 only need 24 bits for each LED, but we add one bit more to keep PWM output low
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let max_duty = ws2812_pwm.max_duty_cycle();
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let n0 = 8 * max_duty / 25; // ws2812 Bit 0 high level timing
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let n1 = 2 * n0; // ws2812 Bit 1 high level timing
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let turn_off = [
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n0, n0, n0, n0, n0, n0, n0, n0, // Green
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n0, n0, n0, n0, n0, n0, n0, n0, // Red
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n0, n0, n0, n0, n0, n0, n0, n0, // Blue
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0, // keep PWM output low after a transfer
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];
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let dim_white = [
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n0, n0, n0, n0, n0, n0, n1, n0, // Green
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n0, n0, n0, n0, n0, n0, n1, n0, // Red
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n0, n0, n0, n0, n0, n0, n1, n0, // Blue
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0, // keep PWM output low after a transfer
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];
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let color_list = &[&turn_off, &dim_white];
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let pwm_channel = Channel::Ch1;
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// make sure PWM output keep low on first start
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ws2812_pwm.channel(pwm_channel).set_duty_cycle(0);
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// flip color at 2 Hz
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let mut ticker = Ticker::every(Duration::from_millis(500));
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loop {
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for &color in color_list {
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// with &mut, we can easily reuse same DMA channel multiple times
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ws2812_pwm.waveform_up(&mut dp.DMA1_CH2, pwm_channel, color).await;
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// ws2812 need at least 50 us low level input to confirm the input data and change it's state
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Timer::after_micros(50).await;
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// wait until ticker tick
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ticker.next().await;
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}
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}
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}
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