embassy/examples/stm32g0/src/bin/spi_neopixel.rs

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#![no_std]
#![no_main]
#![feature(type_alias_impl_trait)]
use defmt::*;
use embassy_executor::Spawner;
use embassy_stm32::dma::word::U5;
use embassy_stm32::dma::NoDma;
use embassy_stm32::spi::{Config, Spi};
use embassy_stm32::time::Hertz;
use embassy_time::{Duration, Timer};
use {defmt_rtt as _, panic_probe as _};
const NR_PIXELS: usize = 15;
const BITS_PER_PIXEL: usize = 24; // 24 for rgb, 32 for rgbw
const TOTAL_BITS: usize = NR_PIXELS * BITS_PER_PIXEL;
struct RGB {
r: u8,
g: u8,
b: u8,
}
impl Default for RGB {
fn default() -> RGB {
RGB { r: 0, g: 0, b: 0 }
}
}
pub struct Ws2812 {
// Note that the U5 type controls the selection of 5 bits to output
bitbuffer: [U5; TOTAL_BITS],
}
impl Ws2812 {
pub fn new() -> Ws2812 {
Ws2812 {
bitbuffer: [U5(0); TOTAL_BITS],
}
}
fn len(&self) -> usize {
return NR_PIXELS;
}
fn set(&mut self, idx: usize, rgb: RGB) {
self.render_color(idx, 0, rgb.g);
self.render_color(idx, 8, rgb.r);
self.render_color(idx, 16, rgb.b);
}
// transform one color byte into an array of 8 byte. Each byte in the array does represent 1 neopixel bit pattern
fn render_color(&mut self, pixel_idx: usize, offset: usize, color: u8) {
let mut bits = color as usize;
let mut idx = pixel_idx * BITS_PER_PIXEL + offset;
// render one bit in one spi byte. High time first, then the low time
// clock should be 4 Mhz, 5 bits, each bit is 0.25 us.
// a one bit is send as a pulse of 0.75 high -- 0.50 low
// a zero bit is send as a pulse of 0.50 high -- 0.75 low
// clock frequency for the neopixel is exact 800 khz
// note that the mosi output should have a resistor to ground of 10k,
// to assure that between the bursts the line is low
for _i in 0..8 {
if idx >= TOTAL_BITS {
return;
}
let pattern = match bits & 0x80 {
0x80 => 0b0000_1110,
_ => 0b000_1100,
};
bits = bits << 1;
self.bitbuffer[idx] = U5(pattern);
idx += 1;
}
}
}
#[embassy_executor::main]
async fn main(_spawner: Spawner) {
let p = embassy_stm32::init(Default::default());
info!("Start test using spi as neopixel driver");
let mut spi = Spi::new_txonly_nosck(p.SPI1, p.PB5, p.DMA1_CH3, NoDma, Hertz(4_000_000), Config::default());
let mut neopixels = Ws2812::new();
loop {
let mut cnt: usize = 0;
for _i in 0..10 {
for idx in 0..neopixels.len() {
let color = match (cnt + idx) % 3 {
0 => RGB { r: 0x21, g: 0, b: 0 },
1 => RGB { r: 0, g: 0x31, b: 0 },
_ => RGB { r: 0, g: 0, b: 0x41 },
};
neopixels.set(idx, color);
}
cnt += 1;
// start sending the neopixel bit patters over spi to the neopixel string
spi.write(&neopixels.bitbuffer).await.ok();
Timer::after(Duration::from_millis(500)).await;
}
Timer::after(Duration::from_millis(1000)).await;
}
}