A techBASIC program for controlling an RC car via a RedBearLabs BLE shield on an Arduino running firmata and a jumpered motor shield.

BLECarDrag.bas

! This app uses the accelerometer to control a car hacked to use the
! RedBear BLE Shield and an Arduino.

redBearUUID$ = "713D0000-503E-4C75-BA94-3148F18D941E"
txUUID$ = "713D0003-503E-4C75-BA94-3148F18D941E"

! The reason I am putting a button over the drag area is because I want to fill
! it with a gradient representing the speed and direction, and the button is the
! only GUI element I know of that can draw a gradient.  Unfortunately, to get
! the drag events, I have to disable the button, which messes up the colors.
DIM dragArea AS Button
DIM status AS Label

DIM updateGradient AS INTEGER
DIM speed AS SINGLE
DIM turn AS SINGLE
DIM lastGradientUpdate AS DOUBLE
lastGradientUpdate = 0

DIM BLEShield AS BLEPeripheral
DIM txCharacteristic AS BLECharacteristic
DIM lastTime AS DOUBLE
haveConnection = 0
oldPout = 0
oldSpeedOut = 0
oldTurnOut = 0

! Set up motor controls
forwardMask  = $04
backwardMask = $00
leftMask    = $00
rightMask    = $10
brakeMask    = $40

! Draw the GUI and start looking for the RedBear BLE Shield
setUp


! Called when a peripheral is found. If it is a RedBear BLE shield, we
! initiate a connection to it and stop scanning for peripherals.
!
! Parameters:
!    time - The time when the peripheral was discovered.
!    peripheral - The peripheral that was discovered.
!    services - List of services offered by the device.
!    advertisements - Advertisements (information provided by the
!        device without the need to read a service/characteristic)
!    rssi - Received Signal Strength Indicator
SUB BLEDiscoveredPeripheral( _
    time AS DOUBLE, _
    peripheral AS BLEPeripheral, _
    services() AS STRING, _
    advertisements(,) AS STRING, _
    rssi)
  BLE.connect(peripheral)
  BLE.stopScan
  BLEShield = peripheral
  haveConnection = 1
END SUB

! Called to report information about the connection status of the
! peripheral or to report that services have been discovered.
!
! Parameters:
!    time - The time when the information was received.
!    peripheral - The peripheral.
!    kind - The kind of call. One of
!        1 - Connection completed
!        2 - Connection failed
!        3 - Connection lost
!        4 - Services discovered
!    message - For errors, a human-readable error message.
!    err - If there was an error, the Apple error number. If there
!        was no error, this value is 0.
SUB BLEPeripheralInfo( _
    time AS DOUBLE, _
    peripheral AS BLEPeripheral, _
    kind AS INTEGER, _
    message AS STRING, _
    err AS LONG)
  DIM uuid(1) AS STRING
  IF kind = 1 THEN
    ! The connection was established. Discover the service.
    uuid(1) = redBearUUID$
    peripheral.discoverServices(uuid)
    status.setBackgroundColor(1, 0.6, 0): ! Connection made: Status Yellow.
  ELSE IF kind = 2 OR kind = 3 THEN
    ! Lost the connection--Change the status and begin looking again.
    status.setBackgroundColor(1, 0, 0): ! Connection lost: Status Red.
    haveConnection = 0
    BLE.connect(peripheral)
  ELSE IF kind = 4 THEN
    ! Once the RedBear service is found, start discovery on the characteristics.
    DIM availableServices(1) AS BLEService
    availableServices = peripheral.services
    FOR a = 1 TO UBOUND(availableServices, 1)
      IF availableServices(a).UUID = redBearUUID$ THEN
        uuid(1) = txUUID$
        peripheral.discoverCharacteristics(uuid, availableServices(a))
      END IF
    NEXT
  END IF
END SUB

! Called to report information about a characteristic or included
! services for a service. If it is one we are interested in, start
! handling it.
!
! Parameters:
!    time - The time when the information was received.
!    peripheral - The peripheral.
!    service - The service whose characteristic or included
!        service was found.
!    kind - The kind of call. One of
!        1 - Characteristics found
!        2 - Included services found
!    message - For errors, a human-readable error message.
!    err - If there was an error, the Apple error number. If there
!        was no error, this value is 0.
SUB BLEServiceInfo( _
    time AS DOUBLE, _
    peripheral AS BLEPeripheral, _
    service AS BLEService, _
    kind AS INTEGER, _
    message AS STRING, _
    err AS LONG)
  IF kind = 1 THEN
    ! Get the characteristics.
    DIM characteristics(1) AS BLECharacteristic
    characteristics = service.characteristics
    FOR i = 1 TO UBOUND(characteristics, 1)
      IF characteristics(i).uuid = txUUID$ THEN
        ! Remember the transmit service.
        txCharacteristic = characteristics(i)

        ! Connection complete: Status Green.
        status.setBackgroundColor(0, 1, 0)
        haveConnection = 1

        ! Set the mode for the pins used.
        inputMode% = $00
        outputMode% = $01
        pwmMode% = $03
        DIM pinModes(2 TO 6) AS INTEGER
        pinModes = [
          outputMode%,  ! Pin 2: Drive direction
          pwmMode%,    ! Pin 3: Drive speed
          outputMode%,  ! Pin 4: Turn direction
          pwmMode%,    ! Pin 5: Turn intensity
  outputMode%  ! Pin 6: Brake
        ]
        DIM value(0) AS INTEGER
        FOR pin = LBOUND(pinModes, 1) TO UBOUND(pinModes, 1)
          value = [ $F4, pin, pinModes(pin) ]
          BLEShield.writeCharacteristic(txCharacteristic, value, 0)
        NEXT
      END IF
    NEXT
  END IF
END SUB

! Set up the GUI and start searching for the RedBear BLE Shield
SUB setUp
  graphics.setToolsHidden(1)
  system.showGraphics
  system.setAllowedOrientations($0001)

  dragSize = graphics.width
  dragArea = graphics.newButton(0,graphics.height-dragSize,dragSize,dragSize)
  ! Mark button as disabled so we can do our own event handling.
  dragArea.setEnabled(0)

  DIM title AS Label
  title = graphics.newLabel(0,0, graphics.width-20)
  title.setText("Version 1")

  status = graphics.newLabel(graphics.width-20,0,20,20)
  status.setBackgroundColor(1, 0, 0)

  engageBrake

  ! Find the BLE Shield.
  BLE.startBLE
  DIM uuid(1) AS STRING
  uuid(1) = redBearUUID$
  BLE.startScan(uuid)
END SUB

SUB touchesBegan(e AS EVENT)
  recordDrag(e)
END SUB

SUB touchesMoved(e AS EVENT)
  recordDrag(e)
END SUB

SUB touchesCanceled(e AS EVENT)
  engageBrake
END SUB

SUB touchesEnded(e AS EVENT)
  engageBrake
END SUB

SUB recordDrag(e AS EVENT)
  IF eventInside(e,dragArea) THEN
    where = e.where
    location = eventLocation(e, dragArea)
    ! Make the multiplier a bit more than 2 because dragging all the way to
    ! the edge of the widget for maximum speed is difficult.
    turn = 2.5*(location(1) - 0.5)
    speed = 2.5*(0.5 - location(2))
    updateGradient = 1
    IF lastGradientUpdate + 0.2 < e.when THEN
      drawSpeed
      lastGradientUpdate = e.when
    END IF
    sendMotorCommands(0)
    e.setConsumed(1)
  END IF
END SUB

FUNCTION eventInside( _
      e AS EVENT, _
      widget AS CONTROL )
  where = e.where
  x = where(1,1)
  y = where(1,2)
  IF x >= widget.x _
    AND y >= widget.y _
    AND x <= widget.x + widget.width _
    AND y <= widget.y + widget.height _
  THEN
    eventInside = 1
  ELSE
    eventInside = 0
  END IF
END FUNCTION

FUNCTION eventLocation( _
      e AS EVENT, _
      widget AS CONTROL ) (0)
  where = e.where
  x = where(1,1)
  y = where(1,2)
  eventLocation = [ _
      (x - widget.x)/widget.width, _
      (y - widget.y)/widget.height ]
END FUNCTION

SUB engageBrake
  updateGradient = 0
  speed = 0
  turn = 0
  dragArea.setBackgroundColor(0.5,0.5,0.5,3)
  dragArea.setGradient(0,0,0,-1,3)
  sendMotorCommands(1)
END SUB

SUB drawSpeed
  IF updateGradient THEN
    updateGradient = 0
    mag = sqr(speed*speed+turn*turn)
    IF mag > 1 THEN mag = 1
    dragArea.setBackgroundColor(1,1-mag,1-mag)
    dragArea.setGradientColor(1,1,1)
    dragArea.setGradient(0.5*turn+0.5, 0.5-0.5*speed, 0.5, 0.5, 3)
    !dragArea.setEnabled(1)
    !dragArea.setEnabled(0)
  END IF
END SUB

! Sends updated moter commands to the car.  If brake is true, state is changed
! to stop running and turn on brake.
SUB sendMotorCommands(brake AS INTEGER)
  IF haveConnection THEN
    DIM pout AS INTEGER, speedOut AS INTEGER, turnOut AS INTEGER
    IF brake THEN
      pout = brakeMask
      speedOut = 0
      turnOut = 0
      speed = 0
      turn = 0
    ELSE
      pout = 0
      IF speed < 0 THEN
        pout = pout BITOR backwardMask
        speedOut = -255*speed
      ELSE
        pout = pout BITOR forwardMask
        speedOut = 255*speed
      END IF
      IF speedOut > 255 THEN speedOut = 255
      IF turn < 0 THEN
        pout = pout BITOR leftMask
        turnOut = -255*turn
      ELSE
        pout = pout BITOR rightMask
        turnOut = 255*turn
      END IF
      IF turnOut > 255 THEN turnOut = 255
    END IF

    ! Send new instructions as necessary.
    IF oldPout <> pout OR brake THEN
      oldPout = pout
      DIM value(3) AS INTEGER
      value = [ $90, (pout BITAND $7F), (pout >> 7) ]
      BLEShield.writeCharacteristic(txCharacteristic, value, 0)
    END IF
    IF oldSpeedOut <> speedOut OR brake THEN
      oldSpeedOut = speedOut
      DIM value(3) AS INTEGER
      value = [ $E3, (speedOut BITAND $7F), (speedOut >> 7) ]
      BLEShield.writeCharacteristic(txCharacteristic, value, 0)
    END IF
    IF oldTurnOut <> turnOut OR brake THEN
      oldTurnOut = turnOut
      DIM value(3) AS INTEGER
      value = [ $E5, (turnOut BITAND $7F), (turnOut >> 7) ]
      BLEShield.writeCharacteristic(txCharacteristic, value, 0)
    END IF
  END IF
END SUB