Add GET_NUM_PIXELS command to BiblioPixel DriverSerial

firmware_code.ino

    enum CMDTYPE
    {
        SETUP_DATA = 1,
        PIXEL_DATA = 2,
        BRIGHTNESS = 3,
        GETID      = 4,
        SETID      = 5,
        GETVER     = 6,
	      GET_NUM_LEDS = 7
    };

...

// TJS ADDED COMMAND
else if(cmd == CMDTYPE::GET_NUM_LEDS)
   {
	      Serial.write((uint8_t)(NUM_LEDS >> 8));
	      Serial.write((uint8_t)(NUM_LEDS & 0xFF));
    }

python_snippet.py

class MyCMDTYPE(CMDTYPE):
    GET_NUM_PIXELS = 7
    
class MyDriver(DriverSerial):
    def getNumPixels(self):
        packet = DriverSerial._generateHeader(MyCMDTYPE.GET_NUM_PIXELS, 0)
        try:
            self._com.write(packet)
            resp = self._com.read(2)
            if len(resp) == 2:
                out = ord(resp[0]) * 256 + ord(resp[1])
            else:
                raise ValueError('Did not get two bytes back from BP')
            return out
        except serial.SerialException:
            log.error("Problem connecting to serial device.")
            return -1
    
driver = MyDriver(LEDTYPE.GENERIC, args.width*args.height, hardwareID="16C0:0483", dev="/dev/ttyACM0")
assert driver.getNumPixels() == args.width*args.height, 'Drive is not set up for a matrix of size %dx%d' % (
    args.width, args.height
    )