Implement sync (e.g. after reset)

microcontroller/ctrl.py

@@ -24,6 +24,17 @@ with serial.Serial("/dev/ttyUSB0", 115200) as ser:
     FRAME_TIME = 1 / FPS
     t = 0
     
+    def sync():
+        # wait for sync
+        while True:
+            b = ser.readline()
+            if b.strip() == b"Sync.":
+                return
+            
+    sync()
+
+    print("initial sync.")
+
     while True:
         
         loop_start = time.time()
@@ -39,6 +50,12 @@ with serial.Serial("/dev/ttyUSB0", 115200) as ser:
         ser.write(payload)
         ser.flush()
         
+        response = ser.readline()
+        if response.strip() != b"Ack.":
+            print(f"received bad response: {response!r}")
+            sync()
+            continue
+
         t += FRAME_TIME
         t %= 1
         

microcontroller/test.ino

@@ -1,4 +1,7 @@
 unsigned long tic_loop = 0;
+unsigned long time_since_last_sync;
+const unsigned long SYNC_TIMEOUT = 1000;
+
 const unsigned int FRAME_TIME = 20; // 20 ms -> 50 FPS
 
 const size_t UNIVERSE_SIZE = 512;
@@ -15,7 +18,8 @@ void setup()
         // spin until serial is up
     }
     Serial.println();
-    Serial.println("Init.");
+    Serial.println("Sync.");
+    time_since_last_sync = millis();
 
     Serial1.begin(250000, SERIAL_8N2); // DMX
 }
@@ -38,19 +42,30 @@ void send_packet()
 
 bool update_buffer()
 {
+    unsigned long now = millis();
     size_t n = Serial.available();
     if (!n)
+    {
+        // nothing available to read
+        if (now - time_since_last_sync > SYNC_TIMEOUT)
+        {
+            // re-sync
+            bytes_read = 0;
+            Serial.println("Sync.");
+            time_since_last_sync = now;
+        }
+
         return false;
+    }
+    time_since_last_sync = now;
+
     int bytes_received = Serial.read(channels_buffer + bytes_read, std::min(n, UNIVERSE_SIZE - bytes_read));
     bytes_read += bytes_received;
 
-    // Serial.printf("rx n=%d rec=%d total=%d\n", n, bytes_received, bytes_read);
-
     if (bytes_read == UNIVERSE_SIZE)
     {
         bytes_read = 0;
-        // Serial.println();
+        Serial.println("Ack.");
-        // Serial.println("Updated.");
         return true;
     }
     else
@@ -63,18 +78,10 @@ void send_dmx_header()
 {
     Serial1.flush();
     Serial1.begin(90000, SERIAL_8N2);
-    /*
-    while (Serial1.available())
-        Serial1.read();
-    */
     // send the break as a "slow" byte
     Serial1.write(0);
     // switch back to the original baud rate
     Serial1.flush();
     Serial1.begin(250000, SERIAL_8N2);
-    /*
-    while (Serial1.available())
-        Serial1.read();
-    */
     Serial1.write(0); // Start-Byte
 }