         const byte rx_byte = (byte) obd_serial.read();
 
         Serial.write( rx_byte );
+
+        led_state = !led_state;
+        digitalWrite( PIN_LED, led_state );
     }
 }

//
#define PIN_KLINE (12)




// *****************************************************

{
    pinMode( PIN_RX, INPUT );
    pinMode( PIN_TX, INPUT );
    pinMode( PIN_LED, OUTPUT );
    digitalWrite( PIN_LED, led_state );

    delay( STARTUP_DELAY );

