Bluetooth Gatt Server Python

Question

`class TxCharacteristic(Characteristic):
    def __init__(self, bus, index, service):
        Characteristic.__init__(self, bus, index, UART_TX_CHARACTERISTIC_UUID,
                                ['notify'], service)
        self.notifying = False
        GLib.io_add_watch(sys.stdin, GLib.IO_IN, self.on_console_input)

    def on_console_input(self, fd, condition):
        s = fd.readline()
        if s.isspace():
            pass
        else:
            self.send_tx(s)
        return True


    #Send
    def send_tx(self, s):
        if not self.notifying:
            return
        value = []
        if s == "Sync\n":   
            milliseconds = int(round(time.time() * 1000))  
            s= "Time: " + str(milliseconds) + "\n"
            print(str(milliseconds))
    

        for c in s:
            value.append(dbus.Byte(c.encode()))
        self.PropertiesChanged(GATT_CHRC_IFACE, {'Value': value}, [])

    def StartNotify(self):
        if self.notifying:
            return
        self.notifying = True

    def StopNotify(self):
        if not self.notifying:
            return
        self.notifying = False

class RxCharacteristic(Characteristic):
    def __init__(self, bus, index, service):
        Characteristic.__init__(self, bus, index, UART_RX_CHARACTERISTIC_UUID,
                                ['write'], service)

    def WriteValue(self, value, options):
        print('remote: {}'.format(bytearray(value).decode()))


class UartService(Service):
    def __init__(self, bus, index):
        Service.__init__(self, bus, index, UART_SERVICE_UUID, True)
        self.add_characteristic(TxCharacteristic(bus, 0, self))
        self.add_characteristic(RxCharacteristic(bus, 1, self))`

I have 2 characteristics classes RxCharacteristic and TxCharacteristic. I would like to modify the WriteValue method in class RxCharacteristic to be able to call method send_tx in TxCharacteristic. Is there any way to do this?

based on: https://github.com/mengguang/pi-ble-uart-server

I tried calling the TxCharacteristic directly and it did not work

Answer 1

RxCharacteristic instance needs to know TxCharacteristic instance to use it. There are lots of ways to do this. An example (minimising modifications to your provided code) is to modify the TxCharacteristic and UartService classes:

class RxCharacteristic(Characteristic):
    def __init__(self, bus, index, service, tx_char):
        Characteristic.__init__(self, bus, index, UART_RX_CHARACTERISTIC_UUID,
                                ['write'], service)
        self.tx_char = tx_char

    def WriteValue(self, value, options):
        print('remote: {}'.format(bytearray(value).decode()))
        self.tx_char.send_tx("test string")


class UartService(Service):
    def __init__(self, bus, index):
        Service.__init__(self, bus, index, UART_SERVICE_UUID, True)
        tx_char = TxCharacteristic(bus, 0, self)
        self.add_characteristic(tx_char)
        self.add_characteristic(RxCharacteristic(bus, 1, self, tx_char))