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soft-serial
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feat(encode): add CRC calculation

This commit is contained in:
doryan 2025-08-10 20:57:28 +04:00
parent 71d952dce5
commit ca54784e64
1 changed files with 19 additions and 32 deletions
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51
src/lib.rs
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@ -28,8 +28,12 @@ const SECOND_HALF_SERIAL_DELAY: u32 = SERIAL_DELAY - FIRST_HALF_SERIAL_DELAY;
const READING_ADJUST: u32 = 16;
const FIRST_ENTRY_READING: u32 = 30;
const LSB: u8 = 0x01;
const MSB: u8 = 0x80;
const MSB: u16 = 0x0200;
#[inline(always)]
fn crc_calculate(value: u8) -> u8 {
((value >> 6) | (value >> 4) | (value >> 2) | value) & 0x0F
}
pub enum PollError {
NotFound,
@ -53,7 +57,7 @@ where
pub fn poll(&self) -> PollResult {
P::into_output();
delay_cycles(1);
delay_cycles(4);
P::into_pull_up_input();
delay_us(SERIAL_DELAY);
@ -127,31 +131,19 @@ where
{
#[inline(never)]
fn write_byte(&self, transmit_data: u8) {
let (mut data, mut parity_bit) = (transmit_data, 0);
let mut data = ((transmit_data as u16) << 4) | (crc_calculate(transmit_data) as u16);
for _ in 0..8 {
for _ in 0..(u8::BITS + 4) {
if data & MSB == 0 {
P::set_high();
parity_bit ^= 0;
} else {
P::set_low();
parity_bit ^= 1;
}
delay_us(SERIAL_DELAY);
data <<= 1;
}
// Hamming code and CRC are very weightful and slow, so I use simple parity check
if parity_bit == 0 {
P::set_high();
} else {
P::set_low();
}
delay_us(SERIAL_DELAY);
}
}
@ -161,35 +153,30 @@ where
{
#[inline(never)]
fn read_byte(&self) -> ReadByteResult {
let (mut data, mut reciever_parity_bit) = (0, 0);
let mut packet = 0u16;
delay_cycles(FIRST_ENTRY_READING);
for _ in 0..8 {
for _ in 0..(u8::BITS + 4) {
delay_us(FIRST_HALF_SERIAL_DELAY);
data <<= 1;
packet <<= 1;
if P::is_low() {
data |= 1;
reciever_parity_bit ^= 1;
packet |= 1;
} else {
data |= 0;
reciever_parity_bit ^= 0;
packet |= 0;
}
delay_cycles(READING_ADJUST);
delay_us(SECOND_HALF_SERIAL_DELAY);
}
delay_us(FIRST_HALF_SERIAL_DELAY);
let received_crc = (packet & 0x000F) as u8;
let data = packet.overflowing_shr(4).0 as u8;
let calculated_crc = crc_calculate(data);
let transmitter_parity_bit = (P::read() >> P::PIN_NUM) & LSB;
delay_cycles(READING_ADJUST);
delay_us(SECOND_HALF_SERIAL_DELAY);
if reciever_parity_bit == transmitter_parity_bit {
return Err((data, reciever_parity_bit));
if received_crc != calculated_crc {
return Err((received_crc, calculated_crc));
}
Ok(data)