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Updated the pio onewire example

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Marc 2025-04-25 00:43:46 +02:00
parent 2a4b380cb7
commit cd27a8a06b
1 changed files with 54 additions and 50 deletions
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86
examples/rp/src/bin/pio_onewire.rs
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@ -1,4 +1,4 @@
//! This example shows how you can use PIO to read a `DS18B20` one-wire temperature sensor.
//! This example shows how you can use PIO to read one or more `DS18B20` one-wire temperature sensors.
#![no_std]
#![no_main]
@ -6,9 +6,10 @@ use defmt::*;
use embassy_executor::Spawner;
use embassy_rp::bind_interrupts;
use embassy_rp::peripherals::PIO0;
use embassy_rp::pio::{self, InterruptHandler, Pio};
use embassy_rp::pio_programs::onewire::{PioOneWire, PioOneWireProgram};
use embassy_rp::pio::{InterruptHandler, Pio};
use embassy_rp::pio_programs::onewire::{PioOneWire, PioOneWireProgram, PioOneWireSearch};
use embassy_time::Timer;
use heapless::Vec;
use {defmt_rtt as _, panic_probe as _};
bind_interrupts!(struct Irqs {
@ -21,40 +22,60 @@ async fn main(_spawner: Spawner) {
let mut pio = Pio::new(p.PIO0, Irqs);
let prg = PioOneWireProgram::new(&mut pio.common);
let onewire = PioOneWire::new(&mut pio.common, pio.sm0, p.PIN_2, &prg);
let mut onewire = PioOneWire::new(&mut pio.common, pio.sm0, p.PIN_2, &prg);
let mut sensor = Ds18b20::new(onewire);
info!("Starting onewire search");
let mut devices = Vec::<u64, 10>::new();
let mut search = PioOneWireSearch::new();
for _ in 0..10 {
if !search.is_finished() {
if let Some(address) = search.next(&mut onewire).await {
if crc8(&address.to_le_bytes()) == 0 {
info!("Found addres: {:x}", address);
let _ = devices.push(address);
} else {
warn!("Found invalid address: {:x}", address);
}
}
}
}
info!("Search done, found {} devices", devices.len());
loop {
sensor.start().await; // Start a new measurement
onewire.reset().await;
// Skip rom and trigger conversion, we can trigger all devices on the bus immediately
onewire.write_bytes(&[0xCC, 0x44]).await;
Timer::after_secs(1).await; // Allow 1s for the measurement to finish
match sensor.temperature().await {
Ok(temp) => info!("temp = {:?} deg C", temp),
_ => error!("sensor error"),
// Read all devices one by one
for device in &devices {
onewire.reset().await;
onewire.write_bytes(&[0x55]).await; // Match rom
onewire.write_bytes(&device.to_le_bytes()).await;
onewire.write_bytes(&[0xBE]).await; // Read scratchpad
let mut data = [0; 9];
onewire.read_bytes(&mut data).await;
if crc8(&data) == 0 {
let temp = ((data[1] as u32) << 8 | data[0] as u32) as f32 / 16.;
info!("Read device {:x}: {} deg C", device, temp);
} else {
warn!("Reading device {:x} failed", device);
}
}
Timer::after_secs(1).await;
}
}
/// DS18B20 temperature sensor driver
pub struct Ds18b20<'d, PIO: pio::Instance, const SM: usize> {
wire: PioOneWire<'d, PIO, SM>,
}
impl<'d, PIO: pio::Instance, const SM: usize> Ds18b20<'d, PIO, SM> {
pub fn new(wire: PioOneWire<'d, PIO, SM>) -> Self {
Self { wire }
}
/// Calculate CRC8 of the data
fn crc8(data: &[u8]) -> u8 {
let mut temp;
let mut data_byte;
let mut crc = 0;
for b in data {
data_byte = *b;
let mut data_byte = *b;
for _ in 0..8 {
temp = (crc ^ data_byte) & 0x01;
let temp = (crc ^ data_byte) & 0x01;
crc >>= 1;
if temp != 0 {
crc ^= 0x8C;
@ -64,20 +85,3 @@ impl<'d, PIO: pio::Instance, const SM: usize> Ds18b20<'d, PIO, SM> {
}
crc
}
/// Start a new measurement. Allow at least 1000ms before getting `temperature`.
pub async fn start(&mut self) {
self.wire.write_bytes(&[0xCC, 0x44]).await;
}
/// Read the temperature. Ensure >1000ms has passed since `start` before calling this.
pub async fn temperature(&mut self) -> Result<f32, ()> {
self.wire.write_bytes(&[0xCC, 0xBE]).await;
let mut data = [0; 9];
self.wire.read_bytes(&mut data).await;
match Self::crc8(&data) == 0 {
true => Ok(((data[1] as u32) << 8 | data[0] as u32) as f32 / 16.),
false => Err(()),
}
}
}