React-native-ble-plx: Can't monitor device

[WQvist]

According to the docs, I've done the following:

• Scanned for devices
• Connected to device
• device.discoverAllServicesAndCharacteristics
• writeCharacteristicWithResponseForDevice

My problem lies in reading the response I get from sending my command.

RX characteristic is writable, but TX is only notifiable and not readable. Therefore I need to monitor the characteristic with monitorCharacteristicForDevice, however I can't get this to function.

I never recieve neither "Monitor success" nor "monitorDevice called" in the code below. If I run the checkBattery() function after connection it returns "Not monitoring".

How do I read the return?

monitorDevice = () => {
    console.log("monitorDevice called")
    this.manager.monitorCharacteristicForDevice(this.state.connectedTo, SERVICE_UUID, TX_CHARACTERISTIC, (error, characteristic) => {
        if (error) {
            console.error("Error at receiving data from device", error);
            return     
        }
        else{
            this.setState({monitoring:true})
            console.log("Monitor success")
            console.log("Monitor success " + characteristic.value);
            this.state.messagesRecieved.push(characteristic.value)
            return
        }
    })
}

connectAndFetchServicesAndCharacteristics = (device) => {
    this.manager.connectToDevice(device.id, null)
    .then(device => {
        this.setState({connectedTo:device.id})
        console.log('Connection successful\nScan stopped')
        this.manager.stopDeviceScan();
        this.setState({scan: false})
        return device.discoverAllServicesAndCharacteristics()
    })
    .then(device => {
        this.setState({servicesDiscovered: true})
        console.log("Services discovered")
        this.monitorDevice()
        return
    })
    .catch(err => {
        console.log(err)
    })
}

checkBattery = () => {
    if(this.state.monitoring){
        this.manager.writeCharacteristicWithResponseForDevice(this.state.connectedTo,
            SERVICE_UUID, 
            RX_CHARACTERISTIC,
            "YmF0dGVyeQ==")
        .then(characteristic => {
            console.log("Successfully sent: " + characteristic.value)
            return
        })
        .catch(err => {
            console.log(err)
        })
    }
    else{
        alert("Not monitoring")
    }
}

[dariuszseweryn]

this.monitorDevice is a function therefore you must
this.monitorDevice => this.monitorDevice()

[WQvist]

My bad, changed it in my original post. There is still no difference however, other than that I recieve monitorDevice called since I now actually call the function.

[dariuszseweryn]

Good. So now you can show the native logs to see what is happening if your peripheral does indeed send any notifications

[WQvist]

Alright, with verbose loglevel I get "ConnectOperation finished" followed by peripheral info. After I run checkBattery() I get:

D RxBle#ConnectionOperationQueue: QUEUED   CharacteristicWriteOperation(88434918)
D RxBle#ConnectionOperationQueue: STARTED  CharacteristicWriteOperation(88434918)
D RxBle#BluetoothGatt$1: onCharacteristicWrite characteristic=... status=0
V RxBle#BleModule: Write to Characteristic(uuid: ..., id: 8, value: 62617474657279)
D RxBle#ConnectionOperationQueue: FINISHED CharacteristicWriteOperation(88434918) in 121 ms

Nothing happens after that.

[dariuszseweryn]

The interesting part is if notification is properly set. So actually that and write sequence

[WQvist]

Sorry, I don't understand. Do you think both notification and write is not properly set up in the above code?

[dariuszseweryn]

I dunno. I want to check what is going on.

btw. you directly set the state this.state.connectedTo = device.id

[WQvist]

Progress! Hooking the peripheral up to a serial monitor I can see that the received string is basically gibberish. "battery" is received as "m畫mz�". Some type of encoding problem

Edit: Solved it by using base-64 library instead of sending a string that was already base64 encoded.