Bluetooth UART command to move servo only work in one direction

BrendenTB · June 10, 2024, 3:33am

I’m trying to make a servo move up and down 10 degrees depending on the bluetooth on data recieved delineated string value sent from the Serial terminal app on my phone.

The servo will move on the , values, but will not move in the reverse direction or show the arrow on the LEDs using any other string value.

If anyone can look at my code and suggest what might be causing this? ChatGPT doesn;t seem to have an answer.

[My code]https://makecode.microbit.org/S14972-44692-48331-34149

martinwork · June 28, 2024, 3:36pm

Hi Brenden,
Sorry this is a bit late… I think that only one bluetooth on data received block will work. The same applies to serial on data received.

The block specifies what separates commands. To do different things, send a command followed by the delimeter, like “U,” or “D,”. The receiver code can read the string up to the delimeter.

My understanding is that MakeCode registers a handler for the DELIM_MATCH event.

github.com

microsoft/pxt-microbit/blob/master/libs/bluetooth/bluetooth.cpp#L148


      
              unregisterGCObj(buffer);
              return res;
          }
          
          /**
          * Registers an event to be fired when one of the delimiter is matched.
          * @param delimiters the characters to match received characters against.
          */
          //% help=bluetooth/on-uart-data-received
          //% weight=18 blockId=bluetooth_on_data_received block="bluetooth|on data received %delimiters=serial_delimiter_conv"
          void onUartDataReceived(String delimiters, Action body) {
            startUartService();
            uart->eventOn(MSTR(delimiters));
            registerWithDal(MICROBIT_ID_BLE_UART, MICROBIT_UART_S_EVT_DELIM_MATCH, body);
          }
          
          /**
           * Register code to run when the micro:bit is connected to over Bluetooth
           * @param body Code to run when a Bluetooth connection is established
           */
          //% help=bluetooth/on-bluetooth-connected weight=20

which removes any existing handler first.

github.com

microsoft/pxt-microbit/blob/master/libs/core/codal.cpp#L99


      
          #endif
          
              // repeat error 4 times and restart as needed
              microbit_panic_timeout(4);
          }
          
          // ---------------------------------------------------------------------------
          // An adapter for the API expected by the run-time.
          // ---------------------------------------------------------------------------
          
          void registerWithDal(int id, int event, Action a, int flags) {
              uBit.messageBus.ignore(id, event, dispatchForeground);
              uBit.messageBus.listen(id, event, dispatchForeground, a);
              incr(a);
              registerGCPtr(a);
          }
          
          void fiberDone(void *a) {
              decr((Action)a);
              unregisterGCPtr((Action)a);
              release_fiber();

Also CODAL has a single string of delimeters, and setting it twice forgets the previous string.

github.com

lancaster-university/codal-microbit-v2/blob/master/source/bluetooth/MicroBitUARTService.cpp#L568


      
            *
            *            SYNC_SPINWAIT - will return MICROBIT_INVALID_PARAMETER
            *
            *            SYNC_SLEEP - Will configure the event and block the current fiber until the
            *                         event is received.
            *
            * @return MICROBIT_INVALID_PARAMETER if the mode given is SYNC_SPINWAIT, otherwise MICROBIT_OK.
            *
            * @note delimeters are matched on a per byte basis.
            */
          int MicroBitUARTService::eventOn(ManagedString delimeters, MicroBitSerialMode mode)
          {
              if(mode == SYNC_SPINWAIT)
                  return MICROBIT_INVALID_PARAMETER;
          
              //configure our head match...
              this->delimeters = delimeters;
          
              //block!
              if(mode == SYNC_SLEEP)
                  fiber_wait_for_event(MICROBIT_ID_BLE_UART, MICROBIT_UART_S_EVT_DELIM_MATCH);

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Bluetooth UART command to move servo only work in one direction

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