diff --git a/embassy-rp/src/pio_programs/onewire.rs b/embassy-rp/src/pio_programs/onewire.rs index 00783aab0..287ddab41 100644 --- a/embassy-rp/src/pio_programs/onewire.rs +++ b/embassy-rp/src/pio_programs/onewire.rs @@ -1,11 +1,17 @@ //! OneWire pio driver -use crate::pio::{Common, Config, Instance, LoadedProgram, PioPin, ShiftConfig, ShiftDirection, StateMachine}; +use crate::clocks::clk_sys_freq; +use crate::gpio::Level; +use crate::pio::{ + Common, Config, Direction, Instance, LoadedProgram, PioPin, ShiftConfig, ShiftDirection, StateMachine, +}; use crate::Peri; -/// This struct represents an onewire driver program +/// This struct represents a onewire driver program pub struct PioOneWireProgram<'a, PIO: Instance> { prg: LoadedProgram<'a, PIO>, + reset_addr: u8, + next_bit_addr: u8, } impl<'a, PIO: Instance> PioOneWireProgram<'a, PIO> { @@ -13,56 +19,67 @@ impl<'a, PIO: Instance> PioOneWireProgram<'a, PIO> { pub fn new(common: &mut Common<'a, PIO>) -> Self { let prg = pio::pio_asm!( r#" - .wrap_target - again: - pull block - mov x, osr - jmp !x, read - write: - set pindirs, 1 - set pins, 0 - loop1: - jmp x--,loop1 - set pindirs, 0 [31] - wait 1 pin 0 [31] - pull block - mov x, osr - bytes1: - pull block - set y, 7 - set pindirs, 1 - bit1: - set pins, 0 [1] - out pins,1 [31] - set pins, 1 [20] - jmp y--,bit1 - jmp x--,bytes1 - set pindirs, 0 [31] - jmp again - read: - pull block - mov x, osr - bytes2: - set y, 7 - bit2: - set pindirs, 1 - set pins, 0 [1] - set pindirs, 0 [5] - in pins,1 [10] - jmp y--,bit2 - jmp x--,bytes2 - .wrap - "#, - ); - let prg = common.load_program(&prg.program); + ; We need to use the pins direction to simulate open drain output + ; This results in all the side-set values being swapped from the actual pin value + .side_set 1 pindirs - Self { prg } + ; Set the origin to 0 so we can correctly use jmp instructions externally + .origin 0 + + ; Tick rate is 1 tick per 6us, so all delays should be calculated back to that + ; All the instructions have a calculated delay XX in us as [(XX / CLK) - 1]. + ; The - 1 is for the instruction which also takes one clock cyle. + ; The delay can be 0 which will result in just 6us for the instruction itself + .define CLK 6 + + ; Write the reset block after trigger + public reset: + set x, 4 side 0 [(60 / CLK) - 1] ; idle before reset + reset_inner: ; Repeat the following 5 times, so 5*96us = 480us in total + nop side 1 [(90 / CLK) - 1] + jmp x--, reset_inner side 1 [( 6 / CLK) - 1] + ; Fallthrough + + ; Check for presence of one or more devices. + ; This samples 32 times with an interval of 12us after a 18us delay. + ; If any bit is zero in the end value, there is a detection + ; This whole function takes 480us + set x, 31 side 0 [(24 / CLK) - 1] ; Loop 32 times -> 32*12us = 384us + presence_check: + in pins, 1 side 0 [( 6 / CLK) - 1] ; poll pin and push to isr + jmp x--, presence_check side 0 [( 6 / CLK) - 1] + jmp next_bit side 0 [(72 / CLK) - 1] + + ; The low pulse was already done, we only need to delay and poll the bit in case we are reading + write_1: + nop side 0 [( 6 / CLK) - 1] ; Delay before sampling the input pin + in pins, 1 side 0 [(48 / CLK) - 1] ; This writes the state of the pin into the ISR + ; Fallthrough + + ; This is the entry point when reading and writing data + public next_bit: + .wrap_target + out x, 1 side 0 [(12 / CLK) - 1] ; Stalls if no data available in TX FIFO and OSR + jmp x--, write_1 side 1 [( 6 / CLK) - 1] ; Do the always low part of a bit, jump to write_1 if we want to write a 1 bit + in null, 1 side 1 [(54 / CLK) - 1] ; Do the remainder of the low part of a 0 bit + ; This writes 0 into the ISR so that the shift count stays in sync + .wrap + "# + ); + + Self { + prg: common.load_program(&prg.program), + reset_addr: prg.public_defines.reset as u8, + next_bit_addr: prg.public_defines.next_bit as u8, + } } } - /// Pio backed OneWire driver pub struct PioOneWire<'d, PIO: Instance, const SM: usize> { sm: StateMachine<'d, PIO, SM>, + cfg: Config<'d, PIO>, + reset_addr: u8, + next_bit_addr: u8, } impl<'d, PIO: Instance, const SM: usize> PioOneWire<'d, PIO, SM> { @@ -74,37 +91,206 @@ impl<'d, PIO: Instance, const SM: usize> PioOneWire<'d, PIO, SM> { program: &PioOneWireProgram<'d, PIO>, ) -> Self { let pin = common.make_pio_pin(pin); + + sm.set_pin_dirs(Direction::In, &[&pin]); + sm.set_pins(Level::Low, &[&pin]); + let mut cfg = Config::default(); - cfg.use_program(&program.prg, &[]); - cfg.set_out_pins(&[&pin]); + cfg.use_program(&program.prg, &[&pin]); cfg.set_in_pins(&[&pin]); - cfg.set_set_pins(&[&pin]); - cfg.shift_in = ShiftConfig { + + let shift_cfg = ShiftConfig { auto_fill: true, direction: ShiftDirection::Right, threshold: 8, }; - cfg.clock_divider = 255_u8.into(); + cfg.shift_in = shift_cfg; + cfg.shift_out = shift_cfg; + + let divider = (clk_sys_freq() / 1000000) as u16 * 6; + cfg.clock_divider = divider.into(); + sm.set_config(&cfg); + sm.clear_fifos(); + sm.restart(); + unsafe { + sm.exec_jmp(program.next_bit_addr); + } sm.set_enable(true); - Self { sm } - } - /// Write bytes over the wire - pub async fn write_bytes(&mut self, bytes: &[u8]) { - self.sm.tx().wait_push(250).await; - self.sm.tx().wait_push(bytes.len() as u32 - 1).await; - for b in bytes { - self.sm.tx().wait_push(*b as u32).await; + Self { + sm, + cfg, + reset_addr: program.reset_addr, + next_bit_addr: program.next_bit_addr, } } - /// Read bytes from the wire - pub async fn read_bytes(&mut self, bytes: &mut [u8]) { - self.sm.tx().wait_push(0).await; - self.sm.tx().wait_push(bytes.len() as u32 - 1).await; - for b in bytes.iter_mut() { - *b = (self.sm.rx().wait_pull().await >> 24) as u8; + /// Perform an initialization sequence, will return true if a presence pulse was detected from a device + pub async fn reset(&mut self) -> bool { + // The state machine immediately starts running when jumping to this address + unsafe { + self.sm.exec_jmp(self.reset_addr); } + + let rx = self.sm.rx(); + let mut found = false; + for _ in 0..4 { + if rx.wait_pull().await != 0 { + found = true; + } + } + + found + } + + /// Write bytes to the onewire bus + pub async fn write_bytes(&mut self, data: &[u8]) { + let (rx, tx) = self.sm.rx_tx(); + for b in data { + tx.wait_push(*b as u32).await; + + // Empty the buffer that is being filled with every write + let _ = rx.wait_pull().await; + } + } + + /// Read bytes from the onewire bus + pub async fn read_bytes(&mut self, data: &mut [u8]) { + let (rx, tx) = self.sm.rx_tx(); + for b in data { + // Write all 1's so that we can read what the device responds + tx.wait_push(0xff).await; + + *b = (rx.wait_pull().await >> 24) as u8; + } + } + + async fn search(&mut self, state: &mut PioOneWireSearch) -> Option { + if !self.reset().await { + // No device present, no use in searching + state.finished = true; + return None; + } + self.write_bytes(&[0xF0]).await; // 0xF0 is the search rom command + + self.prepare_search(); + + let (rx, tx) = self.sm.rx_tx(); + + let mut value = 0; + let mut last_zero = 0; + + for bit in 0..64 { + // Write 2 dummy bits to read a bit and its complement + tx.wait_push(0x1).await; + tx.wait_push(0x1).await; + let in1 = rx.wait_pull().await; + let in2 = rx.wait_pull().await; + let push = match (in1, in2) { + (0, 0) => { + // If both are 0, it means we have devices with 0 and 1 bits in this position + let write_value = if bit < state.last_discrepancy { + (state.last_rom & (1 << bit)) != 0 + } else { + bit == state.last_discrepancy + }; + + if write_value { + 1 + } else { + last_zero = bit; + 0 + } + } + (0, 1) => 0, // Only devices with a 0 bit in this position + (1, 0) => 1, // Only devices with a 1 bit in this position + _ => { + // If both are 1, it means there is no device active and there is no point in continuing + self.restore_after_search(); + state.finished = true; + return None; + } + }; + value >>= 1; + if push == 1 { + value |= 1 << 63; + } + tx.wait_push(push).await; + let _ = rx.wait_pull().await; // Discard the result of the write action + } + + self.restore_after_search(); + + state.last_discrepancy = last_zero; + state.finished = last_zero == 0; + state.last_rom = value; + Some(value) + } + + fn prepare_search(&mut self) { + self.cfg.shift_in.threshold = 1; + self.cfg.shift_in.direction = ShiftDirection::Left; + self.cfg.shift_out.threshold = 1; + + self.sm.set_enable(false); + self.sm.set_config(&self.cfg); + + // set_config jumps to the wrong address so jump to the right one here + unsafe { + self.sm.exec_jmp(self.next_bit_addr); + } + self.sm.set_enable(true); + } + + fn restore_after_search(&mut self) { + self.cfg.shift_in.threshold = 8; + self.cfg.shift_in.direction = ShiftDirection::Right; + self.cfg.shift_out.threshold = 8; + + self.sm.set_enable(false); + self.sm.set_config(&self.cfg); + + // Clear the state in case we aborted prematurely with some bits still in the shift registers + self.sm.clear_fifos(); + self.sm.restart(); + + // set_config jumps to the wrong address so jump to the right one here + unsafe { + self.sm.exec_jmp(self.next_bit_addr); + } + self.sm.set_enable(true); + } +} + +/// Onewire search state +pub struct PioOneWireSearch { + last_rom: u64, + last_discrepancy: u8, + finished: bool, +} + +impl PioOneWireSearch { + /// Create a new Onewire search state + pub fn new() -> Self { + Self { + last_rom: 0, + last_discrepancy: 0, + finished: false, + } + } + + /// Search for the next address on the bus + pub async fn next(&mut self, pio: &mut PioOneWire<'_, PIO, SM>) -> Option { + if self.finished { + None + } else { + pio.search(self).await + } + } + + /// Is finished when all devices have been found + pub fn is_finished(&self) -> bool { + self.finished } } diff --git a/examples/rp/src/bin/pio_onewire.rs b/examples/rp/src/bin/pio_onewire.rs index 991510851..379e2b8f9 100644 --- a/examples/rp/src/bin/pio_onewire.rs +++ b/examples/rp/src/bin/pio_onewire.rs @@ -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 { @@ -21,63 +22,66 @@ 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::::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; - for _ in 0..8 { - temp = (crc ^ data_byte) & 0x01; - crc >>= 1; - if temp != 0 { - crc ^= 0x8C; - } - data_byte >>= 1; +fn crc8(data: &[u8]) -> u8 { + let mut crc = 0; + for b in data { + let mut data_byte = *b; + for _ in 0..8 { + let temp = (crc ^ data_byte) & 0x01; + crc >>= 1; + if temp != 0 { + crc ^= 0x8C; } - } - 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 { - 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(()), + data_byte >>= 1; } } + crc }