Improve CAN bus robustness: adjust NART, add transmission delays for error recovery.

Software/CAN_Sensor/src/main.rs

@@ -256,12 +256,12 @@ async fn main(spawner: Spawner) {
         
         // Improve CAN robustness for longer cables:
         // 1. Enable Automatic Bus-Off Management (ABOM)
-        // 2. Disable Automatic Retransmission (NART) as we send regular measurements anyway
+        // 2. Enable Automatic Retransmission (NART) to recover from transient errors
         // 3. Enable Receive FIFO Overwrite Mode (RFLM = 0, default)
         // 4. Increase Resync Jump Width (SJW) if possible by patching BTIMR
         hal::pac::CAN1.ctlr().modify(|w| {
             w.set_abom(false);
-            w.set_nart(true); 
+            w.set_nart(false); 
         });
         
         // SJW is bits 24-25 of BTIMR. HAL sets it to 0 (SJW=1). 
@@ -593,11 +593,15 @@ async fn worker(
         log(msg);
 
         let moisture = CanFrame::new(moisture_id, &(freq_hz as u32).to_be_bytes()).unwrap();
+        let delay_ms = moisture_id.as_raw() as u64 % 50;
+        Timer::after(Duration::from_millis(delay_ms)).await;
         CAN_TX_CH.send(moisture).await;
 
         // Send firmware build timestamp after each measurement so the controller
         // always has up-to-date build info without requiring an identify request.
         let firmware = CanFrame::new(firmware_build_id, &FIRMWARE_BUILD_MINUTES.to_be_bytes()).unwrap();
+        let delay_ms = firmware_build_id.as_raw() as u64 % 50;
+        Timer::after(Duration::from_millis(delay_ms)).await;
         CAN_TX_CH.send(firmware).await;
 
         // Wait for the other slot to measure, plus gaps to ensure no overlap