Get the D value of the current PID for position

def get_position_d(self):
        """ Get the D value of the current PID for position

        """
        data = []
        data.append(0x09)
        data.append(self.servoid)
        data.append(RAM_READ_REQ)
        data.append(POSITION_KD_RAM)
        data.append(BYTE2)
        send_data(data)
        rxdata = []
        try:
            rxdata = SERPORT.read(13)
            return (ord(rxdata[10])*256)+(ord(rxdata[9])&0xff)
        except HerkulexError:
            raise HerkulexError("could not communicate with motors")