soft-serial/src/lib.rs

#![no_std]

use core::marker::PhantomData;

use arduino_hal::{
    delay_us,
    hal::port::{PB4, PB5, PE6},
    port::{
        mode::{Input, PullUp},
        Pin, PinOps,
    },
};

use avr_device::asm::delay_cycles;

use static_pins::StaticPinOps;
use ufmt::derive::uDebug;

mod structures;

pub type PollResult = Result<(), PollError>;
pub type ReadByteResult = Result<u8, CorruptedData>;
pub type CorruptedData = (u8, u8);

const SERIAL_DELAY: u32 = 4;
const FIRST_HALF_SERIAL_DELAY: u32 = SERIAL_DELAY / 2;
const SECOND_HALF_SERIAL_DELAY: u32 = SERIAL_DELAY - FIRST_HALF_SERIAL_DELAY;

const READING_ADJUST: u32 = 10;
const TX_DELAY_CYCLES: u32 = 22;
const MSB: u16 = 0x0800;
const PACKET_MASK: u16 = 0x0FFF;

#[inline(always)]
fn crc_calculate(value: u8) -> u8 {
    ((value >> 6) | (value >> 4) | (value >> 2) | value) & 0x0F
}

#[cfg(feature = "ufmt")]
#[derive(uDebug)]
pub enum PollError {
    NotFound,
    NotReady,
}

pub struct HalfDuplexSerial<P> {
    _pin: PhantomData<Pin<Input<PullUp>, P>>,
}

#[cfg(debug_assertions)]
#[inline(always)]
fn debug_pb4_low() {
    PB4::set_low();
}

#[cfg(debug_assertions)]
#[inline(always)]
fn debug_pb4_high() {
    PB4::set_high();
}

#[allow(dead_code)]
#[cfg(debug_assertions)]
#[inline(always)]
fn debug_pb4_pulse_positive() {
    debug_pb4_low();
    debug_pb4_high();
}

#[allow(dead_code)]
#[cfg(debug_assertions)]
#[inline(always)]
fn debug_pb4_pulse_negative() {
    debug_pb4_high();
    debug_pb4_low();
}

impl<P> HalfDuplexSerial<P>
where
    P: PinOps + StaticPinOps,
{
    pub fn new(_pin: Pin<Input<PullUp>, P>) -> Self {
        if cfg!(debug_assertions) {
            PB4::into_output_high();
            PB5::into_output_high();
            PE6::into_output_high();
        }
        Self {
            _pin: PhantomData {},
        }
    }

    pub fn poll(&self) -> PollResult {
        PE6::set_low();
        P::into_output();

        delay_cycles(2);

        P::into_pull_up_input();

        delay_us(SERIAL_DELAY + FIRST_HALF_SERIAL_DELAY);

        if P::is_low() {
            PE6::set_high();
            return PollResult::Err(PollError::NotFound);
        }

        delay_us(SERIAL_DELAY);

        if P::is_high() {
            PE6::set_high();
            return PollResult::Err(PollError::NotReady);
        }

        while P::is_low() {}

        PE6::set_high();

        PollResult::Ok(())
    }

    pub fn response(&self) {
        PE6::set_low();

        P::into_output_high();

        delay_us(FIRST_HALF_SERIAL_DELAY);

        P::set_low();

        delay_us(SERIAL_DELAY);

        P::set_high();
        P::into_pull_up_input();

        PE6::set_high();
    }

    #[inline]
    pub fn sync_transmitter(&self) {
        if cfg!(debug_assertions) {
            PB5::set_low();
        }

        P::into_output();

        delay_us(SERIAL_DELAY);

        P::set_high();

        if cfg!(debug_assertions) {
            PB5::set_high();
        }
    }

    #[inline]
    pub fn sync_reciever(&self) {
        if cfg!(debug_assertions) {
            PB5::set_low();
        }

        while P::is_high() {}

        while P::is_low() {}

        if cfg!(debug_assertions) {
            PB5::set_high();
        }
    }

    #[inline]
    pub fn reset(&self) {
        P::into_pull_up_input();
    }
}

pub trait SoftSerialWriter<P, T>: SoftSerialByteWriter<P>
where
    P: PinOps + StaticPinOps,
{
    fn write_bytes(&self, transmit_data: T);
}

pub trait SoftSerialReader<P, T>: SoftSerialByteReader<P>
where
    P: PinOps + StaticPinOps,
{
    fn read_bytes(&self, recieve_data: T) -> Result<(), CorruptedData>;
}

pub trait SoftSerialByteWriter<P>
where
    P: PinOps + StaticPinOps,
{
    #[inline(never)]
    fn write_byte(&self, transmit_data: u8) {
        let mut data = ((transmit_data as u16) << 4) | (crc_calculate(transmit_data) as u16);

        for _ in 0..(u8::BITS + 4) {
            debug_pb4_low();

            if data & MSB == 0 {
                P::set_high();
            } else {
                P::set_low();
            }

            data = (data << 1) & PACKET_MASK;
            delay_us(SERIAL_DELAY);

            debug_pb4_high();
        }

        P::set_high();
        delay_cycles(TX_DELAY_CYCLES);
    }
}

pub trait SoftSerialByteReader<P>
where
    P: PinOps + StaticPinOps,
{
    #[inline(never)]
    fn read_byte(&self) -> ReadByteResult {
        let mut packet = 0u16;

        for _ in 0..(u8::BITS + 4) {
            debug_pb4_low();

            delay_us(FIRST_HALF_SERIAL_DELAY);
            delay_cycles(READING_ADJUST);

            if P::is_low() {
                packet = (packet << 1) | 1;
            } else {
                packet <<= 1;
            }

            delay_us(SECOND_HALF_SERIAL_DELAY);

            debug_pb4_high();
        }

        let data = (packet >> 4) as u8;
        let received_crc = (packet & 0x000F) as u8;
        let calculated_crc = crc_calculate(data);

        if received_crc != calculated_crc {
            return Err((received_crc, calculated_crc));
        }

        Ok(data)
    }
}

impl<P: PinOps + StaticPinOps> SoftSerialByteWriter<P> for HalfDuplexSerial<P> {}
impl<P: PinOps + StaticPinOps> SoftSerialByteReader<P> for HalfDuplexSerial<P> {}

impl<P> SoftSerialWriter<P, &[u8]> for HalfDuplexSerial<P>
where
    P: PinOps + StaticPinOps,
{
    fn write_bytes(&self, transmit_data: &[u8]) {
        for byte in transmit_data {
            self.write_byte(*byte);
            self.sync_transmitter();
        }
    }
}

impl<P> SoftSerialReader<P, &mut [u8]> for HalfDuplexSerial<P>
where
    P: PinOps + StaticPinOps,
{
    fn read_bytes(&self, recieve_data: &mut [u8]) -> Result<(), CorruptedData> {
        for byte in recieve_data {
            *byte = self.read_byte()?;
            self.sync_reciever();
        }
        Ok(())
    }
}