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Problem trying to iterate CoreBluetooth write/read requests to OBD-II BLE adapter

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Hello! I am new to Swift and I'm working on my senior project for my CS degree coursework.

I am trying to continually iterate through my write/read requests to get live data from the OBD-II bus on my vehicle. I am using CoreBluetooth in Swift to connect and communicate with my OBD-II BLE adapter.

My goal is to constantly update the live data for 4 different sensors while the user is in the LiveDataView() and then stop asking if they leave the view, or the app is set to background/is closed.

I tried a timer. This appears to work, but seems janky. I noticed that as I repetitively ask for PID "0105" (Engine Coolant Temperature), everything seemed to work in the debug console.. but it wasn't actually updating my engine coolant temp in the LiveDataView().

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
    for characteristic in service.characteristics ?? [] {
        if (String(describing: characteristic.uuid)) == "BEF8D6C9-9C21-4C9E-B632-BD58C1009F9F" {
            obdSensorCharacteristic = characteristic
            peripheral.setNotifyValue(true, for: characteristic)
            print("Found \(characteristic), waiting on values:")
            print("Characteristic Value: \(String(describing: characteristic.value))")

            if stopData {
                Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: { timer in

                    if self.stopData == false {

func requestData() {
    if ((obdSensorPeripheral?.canSendWriteWithoutResponse) != nil && sendData) {

        if sendData {
            self.write(value: commands[0], characteristic: self.obdSensorCharacteristic!)
            self.read(characteristic: self.obdSensorCharacteristic!)


Is there a better way to continually write/read information from the OBD-II BLE device? Is there a better way to control write/reads to the peripheral characteristic?


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