send receive nrz working

2sem_sem2/src/receive.rs

@@ -1,7 +1,32 @@
 use defmt::info;
 use embassy_stm32::exti::ExtiInput;
-use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, channel::Receiver};
-use embassy_time::Timer;
+use embassy_time::{Duration, Timer};
+
+const START: u8 = 0x7E;
+const STOP: u8 = 0x81;
+const MAX_PAYLOAD: usize = 64;
+
+fn crc8(crc: u8, byte: u8) -> u8 {
+    let mut c = crc ^ byte;
+    for _ in 0..8 {
+        c = if c & 0x80 != 0 {
+            (c << 1) ^ 0x07
+        } else {
+            c << 1
+        };
+    }
+    c
+}
+
+async fn sample_byte(pin: &mut ExtiInput<'static>, bit_time: Duration) -> u8 {
+    let mut byte = 0u8;
+    for _ in 0..8 {
+        let bit = if pin.is_high() { 1 } else { 0 };
+        byte = (byte << 1) | bit;
+        Timer::after(bit_time).await;
+    }
+    byte
+}
 
 #[embassy_executor::task]
 pub async fn bit_receive_and_decode(mut pin: ExtiInput<'static>) {
@@ -13,59 +38,70 @@ pub async fn bit_receive_and_decode(mut pin: ExtiInput<'static>) {
         pin.wait_for_rising_edge().await;
         let bit_time = embassy_time::Instant::now().duration_since(t1);
 
-        let _ = Timer::after(bit_time).await;
-
-        let mut message_buffer = [0u8; 8]; // sprava
-        let mut byte_idx = 0;
-        let mut frame_active = true;
-
-        while frame_active && byte_idx < message_buffer.len() {
-            let mut current_byte = 0u8;
-
-            for _ in 0..8 {
-                let bit = if pin.is_high() { 1 } else { 0 };
-                current_byte = (current_byte << 1) | bit;
-                Timer::after(bit_time).await;
-            }
-
-            if current_byte == 0xAA {
-                frame_active = false;
-            } else {
-                message_buffer[byte_idx] = current_byte;
-                byte_idx += 1;
-            }
+        Timer::after(bit_time / 2).await;
+        let mut start_byte = 0u8;
+        for _ in 0..7 {
+            let bit = if pin.is_high() { 1 } else { 0 };
+            start_byte = (start_byte << 1) | bit;
+            Timer::after(bit_time).await;
         }
 
-        if let Ok(s) = core::str::from_utf8(&message_buffer[..byte_idx]) {
-            info!("sprava: {}", s);
-        }
-    }
-}
-
-#[embassy_executor::task]
-pub async fn bit_decode(receiver: Receiver<'static, CriticalSectionRawMutex, u8, 64>) {
-    let mut buffer = 0u64;
-    loop {
-        let bit = receiver.receive().await;
-        buffer = (buffer << 1) | (bit as u64);
-
-        // sync 0xAA + start 0xAB
-        if (buffer & 0xFFFF) == 0xAAAB {
-            info!("frame");
-            let mut message = [0u8; 4];
-
-            for byte in message.iter_mut() {
-                for _ in 0..8 {
-                    let b = receiver.receive().await;
-                    *byte = (*byte << 1) | b;
-                }
-            }
-
-            if let Ok(s) = core::str::from_utf8(&message) {
-                info!("Received: {}", s);
-            }
-
-            buffer = 0;
+        if start_byte != START {
+            info!("start fail: 0x{:02X}", start_byte);
+            continue;
+        }
+
+        // len
+        let len = sample_byte(&mut pin, bit_time).await;
+        if len as usize > MAX_PAYLOAD {
+            info!("bad len {}", len);
+            continue;
+        }
+
+        // payload
+        let mut payload = [0u8; MAX_PAYLOAD];
+        for i in 0..(len as usize) {
+            payload[i] = sample_byte(&mut pin, bit_time).await;
+        }
+
+        // crc
+        let crc_recv = sample_byte(&mut pin, bit_time).await;
+
+        // parita
+        let parity_recv = if pin.is_high() { 1 } else { 0 };
+        Timer::after(bit_time).await;
+
+        // stop
+        let stop = sample_byte(&mut pin, bit_time).await;
+        if stop != STOP {
+            info!("bad stop 0x{:02X}", stop);
+            continue;
+        }
+
+        // verify CRC
+        let mut crc_calc = crc8(0, len);
+        for i in 0..(len as usize) {
+            crc_calc = crc8(crc_calc, payload[i]);
+        }
+        if crc_calc != crc_recv {
+            info!("crc nesedi 0x{:02X} ma byt 0x{:02X}", crc_recv, crc_calc);
+            continue;
+        }
+
+        // verify parity
+        let mut ones = len.count_ones() + crc_recv.count_ones();
+        for i in 0..(len as usize) {
+            ones += payload[i].count_ones();
+        }
+        if (ones as u8 & 1) != parity_recv {
+            info!("nesedi parita");
+            continue;
+        }
+
+        if let Ok(s) = core::str::from_utf8(&payload[..len as usize]) {
+            info!("RX OK: \"{}\"", s);
+        } else {
+            info!("RX OK: {} bytes", len);
         }
     }
 }