bitbang uart rx

serial.rs

impl <TX, RX, Delay> serial::Read<u8> for Serial <TX, RX, Delay>
where 
    TX: OutputPin,
    RX: InputPin,
    Delay: DelayUs<u32> 
{

    type Error = ();

    fn read(&mut self) -> nb::Result<u8, Self::Error> {
        if self.reading || self.writing {
            return Err(nb::Error::WouldBlock)
        }
        let mut data_in = 0;
        // wait for start bit
        if self.rx.is_high() {
            return Err(nb::Error::WouldBlock) 
        }
        self.reading = true;
        self.delay.delay_us((self.delay_time as f32 * 1.5) as u32); 
        let mut buf: u16 = 0;
        for _ in 0..8 {
            let mut bit: u8 = 0;
            for _ in 0..4 {
                buf <<= 1;
                if self.rx.is_high() {
                    buf |= 1;  
                }
                if buf == 0b0011 || buf == 0b1110 || buf == 0b0111 || buf == 0b1100 || buf == 0b0110 || buf == 0b1111{
                    bit = 1;
                }
                self.delay.delay_us(self.delay_time/4);
            }
            data_in <<= 1;
            data_in |= bit;
        }
        // wait for stop bit
        self.delay.delay_us(self.delay_time);
        self.reading = false;
        Ok(data_in)
    }
}