149 lines
4.2 KiB
Rust
149 lines
4.2 KiB
Rust
use embedded_hal::spi::FullDuplex;
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use embedded_hal::digital::v2::{InputPin, OutputPin};
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use embedded_hal::blocking::spi::Transfer;
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use nb::Error::WouldBlock;
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/// Bit-banged Mode3 SPI
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pub struct SoftSpi<SCK, MOSI, MISO> {
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sck: SCK,
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mosi: MOSI,
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miso: MISO,
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state: State,
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input: Option<u8>,
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}
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#[derive(PartialEq)]
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enum State {
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Idle,
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Transfer {
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clock_phase: bool,
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mask: u8,
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output: u8,
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input: u8,
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},
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}
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impl<SCK: OutputPin, MOSI: OutputPin, MISO: InputPin> SoftSpi<SCK, MOSI, MISO> {
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pub fn new(mut sck: SCK, mut mosi: MOSI, miso: MISO) -> Self {
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let _ = sck.set_high();
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let _ = mosi.set_low();
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SoftSpi {
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sck, mosi, miso,
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state: State::Idle,
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input: None,
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}
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}
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/// Call this at twice the data rate
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pub fn tick(&mut self) {
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match self.state {
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State::Idle => {}
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State::Transfer { clock_phase: false,
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mask, output, input } => {
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if output & mask != 0 {
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let _ = self.mosi.set_high();
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} else {
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let _ = self.mosi.set_low();
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}
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let _ = self.sck.set_low();
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self.state = State::Transfer {
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clock_phase: true,
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mask, output, input,
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};
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}
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State::Transfer { clock_phase: true,
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mask, output, mut input } => {
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if self.miso.is_high().unwrap_or(false) {
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input |= mask;
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}
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let _ = self.sck.set_high();
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if mask != 1 {
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self.state = State::Transfer {
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clock_phase: false,
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mask: mask >> 1,
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output, input,
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};
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} else {
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self.input = Some(input);
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self.state = State::Idle;
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}
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}
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}
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}
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pub fn run<F: FnMut()>(&mut self, delay: &'_ mut F) {
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while self.state != State::Idle {
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self.tick();
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delay();
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}
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}
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}
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impl<SCK: OutputPin, MOSI: OutputPin, MISO: InputPin> FullDuplex<u8> for SoftSpi<SCK, MOSI, MISO> {
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type Error = ();
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fn read(&mut self) -> Result<u8, nb::Error<Self::Error>> {
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match self.input.take() {
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Some(input) =>
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Ok(input),
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None if self.state == State::Idle =>
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Err(nb::Error::Other(())),
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None =>
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Err(WouldBlock),
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}
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}
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fn send(&mut self, output: u8) -> Result<(), nb::Error<Self::Error>> {
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match self.state {
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State::Idle => {
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self.state = State::Transfer {
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clock_phase: false,
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mask: 0x80,
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output,
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input: 0,
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};
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Ok(())
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}
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_ => Err(WouldBlock)
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}
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}
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}
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pub struct SyncSoftSpi<'d, SCK: OutputPin, MOSI: OutputPin, MISO: InputPin, D: FnMut()> {
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spi: SoftSpi<SCK, MOSI, MISO>,
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delay: &'d mut D,
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}
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impl<'d, SCK: OutputPin, MOSI: OutputPin, MISO: InputPin, D: FnMut()> SyncSoftSpi<'d, SCK, MOSI, MISO, D> {
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pub fn new(spi: SoftSpi<SCK, MOSI, MISO>, delay: &'d mut D) -> Self {
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SyncSoftSpi { spi, delay }
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}
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fn retry<R, E, F>(&mut self, f: &F) -> Result<R, E>
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where
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F: Fn(&'_ mut SoftSpi<SCK, MOSI, MISO>) -> Result<R, nb::Error<E>>
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{
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loop {
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match f(&mut self.spi) {
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Ok(r) => return Ok(r),
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Err(nb::Error::Other(e)) => return Err(e),
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Err(WouldBlock) => self.spi.run(self.delay),
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}
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}
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}
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}
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impl<'d, SCK: OutputPin, MOSI: OutputPin, MISO: InputPin, D: FnMut()> Transfer<u8> for SyncSoftSpi<'d, SCK, MOSI, MISO, D> {
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// TODO: proper type
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type Error = ();
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fn transfer<'w>(&mut self, words: &'w mut [u8]) -> Result<&'w [u8], Self::Error> {
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for b in words.iter_mut() {
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self.retry(&|spi| spi.send(*b))?;
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*b = self.retry(&|spi| spi.read())?;
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}
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Ok(words)
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}
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}
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