cargo fmt + max size of a payload at send

2sem_sem2/src/bin/main.rs

@@ -10,9 +10,8 @@ use embassy_stm32::gpio::{Output, Pull};
 use embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex;
 use embassy_sync::channel::Channel;
 use embassy_time::Duration;
-use semestralka2::receive::bit_receive_and_decode;
 use semestralka2::level_for_bit;
-use semestralka2::send::Tx;
+use semestralka2::receive::bit_receive_and_decode;
 use semestralka2::send::{bit_send, msg_encode};
 
 use {defmt_rtt as _, panic_probe as _};

2sem_sem2/src/send.rs

@@ -7,10 +7,11 @@ use embassy_sync::{
 };
 use embassy_time::{Duration, Ticker};
 
-use crate::{level_for_bit, Encoding};
+use crate::{Encoding, level_for_bit};
 
 const START: u8 = 0x7E;
 const STOP: u8 = 0x81;
+const MAX_PAYLOAD: usize = 64;
 const BIT_PERIOD: Duration = Duration::from_millis(10);
 
 pub type Tx = Sender<'static, CriticalSectionRawMutex, u8, 128>;
@@ -26,7 +27,11 @@ async fn send_byte(byte: u8, tx: &Tx) {
 }
 
 /// [START] [LEN] [PAYLOAD ...] [CRC] [P] [STOP]
-pub async fn msg_encode(payload: &[u8], tx: &Tx) {
+pub async fn msg_encode(payload: &[u8], tx: &Tx) -> Result<(), ()> {
+    if payload.len() > MAX_PAYLOAD {
+        return Err(());
+    }
+
     // start
     send_byte(START, tx).await;
 
@@ -54,6 +59,8 @@ pub async fn msg_encode(payload: &[u8], tx: &Tx) {
 
     // idle
     tx.send(1).await;
+
+    Ok(())
 }
 
 fn crc8(crc: u8, byte: u8) -> u8 {