I'm developing and app for iOS which needs to connect to a Bluetooth Device. I've been able to find and connect to devices near me using CoreBluetooth and GATT profile. The writing and reading of characteristics worked as well. These values will eventually be written when a slider is moved. However, now I also need to be able to stream audio to the Bluetooth Device.
When I looked around for streaming audio over bluetooth I noticed this could be done with AVFoundation by allowing output over bluetooth. However, then the device has to use A2DP profile. But this causes the app to be unable to read/write characteristics?
I got this piece of code to read, notify and write to specific characteristics.
func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService,
error: Error?) {
guard let characteristics = service.characteristics else { return }
for characteristic in characteristics {
print(characteristic)
if characteristic.properties.contains(.read) {
print("\(characteristic.uuid): properties contains .read")
if characteristic.uuid == batteryLevelCharacteristicCBUUID { peripheral.readValue(for: characteristic) }
}
if characteristic.properties.contains(.notify) {
print("\(characteristic.uuid): properties contains .notify")
if characteristic.uuid == batteryLevelCharacteristicCBUUID {
peripheral.setNotifyValue(true, for: characteristic)
}
}
if characteristic.properties.contains(.write) {
print("\(characteristic.uuid): properties contains .write")
if characteristic.uuid == writeTestCharacteristicCBUUID {
print("Writing characteristic found! Trying to write now.")
let string = "Hello World!"
let data = string.data(using: .utf8)!
peripheral.writeValue(data, for: characteristic, type: CBCharacteristicWriteType.withResponse)
}
}
}
}
This question seems similar but it is mentioned that it's not possible. Is possible send hexadecimal data to A2DP Bluetooth Device in swift?
However, I was thinking. If you look at a headset for example when you press buttons there has to be some data transfer. Can this somehow be used for what I want to do? But I can't seem to find any information about these signals or how to use those in my code.
So what I want is to be able to stream the audio and also send small values like percentages.
If you know any information that might help me please let me know. Thanks in advance!
Related
I am developing an iOS app using BLE, I have the BLE comms working but I do not seem to receive any data. The plan is to use multiple BLE UUID characteristics to send data from our ECU to the iOS mobile app. I know the BLE ECU is working as I have checked it with a BLE scanner.
I have followed this example, but still cannot get the BLE read to work correctly. Oddly if read the bytes back one by one I get the required data, but I cannot seem to find a solution to read the complete string in one go? I could use a loop to read all the data back, but surely there must be a way to read back the BLE receive buffer in one go?
https://www.freecodecamp.org/news/ultimate-how-to-bluetooth-swift-with-hardware-in-20-minutes/
Any help would be highly appreciated.
func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
var characteristicASCIIValue = NSString()
guard characteristic == rxCharacteristic,
let characteristicValue = characteristic.value,
let ASCIIstring = NSString(data: characteristicValue, encoding: String.Encoding.utf8.rawValue) else { return }
print("Value Recieved: \((characteristicASCIIValue as String))")
if(characteristic.uuid.isEqual(CBUUIDs.ECU_UUID_A)
{
print ("Found ECU_UUID_A")
Extract_ECU_UUID_A(ASCIIstring)
}
else if(characteristic.uuid.isEqual(CBUUIDs.ECU_UUID_B)
{
print ("Found ECU_UUID_B")
Extract_ECU_UUID_B(ASCIIstring)
}
}
I'm developing app which reads specific characteristics in the background mode. Can this be achieved in the background with selecting the background mode as "Uses Bluetooth LE Accessories" in the plist. Is there any chances of rejecting the app in background if we read particular characteristics of a known service? Reading the characteristics should happen continuously. If we setNotify to "True" will this work in the background. Please provide some valuable suggestions/work around if anyone is aware of it. Thanks in advance.
Can this be achieved in the background with selecting the background mode as "Uses Bluetooth LE Accessories" in the plist.
Yes you can definitely read ble characteristics when your app is in background mode setting the “Uses Bluetooth LE Accessories” background mode in the capabilities tab
Is there any chances of rejecting the app in background if we read particular characteristics of a known service?
If your app needs ble background mode and correctly declares it in the capabilities tab, the app won’t be rejected
Reading the characteristics should happen continuously. If we setNotify to "True" will this work in the background
In order to get notified each time the ble characteristic of your ble peripheral changes its value, you can correctly setNotify to true on the desired characteristic. Each time the characteristic changes its value the peripheral(_:didUpdateStateFor:Error) callback will be triggered and you can get the updated value. Setting the background mode correctly, this callback will be triggered even if your application is in background and your phone is locked.
func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic,
error: Error?)
{
print("characteristic: ", characteristic)
guard let string = String(bytes: characteristic.value!, encoding: .utf8) else {
return
}
}
Capabilities -> On Background Modes -> Select External accessory communication & Uses Bluetooth LE accessories
func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService,
error: Error?) {
guard let characteristics = service.characteristics else { return }
for characteristic in characteristics {
print(characteristic)
if characteristic.properties.contains(.read) {
print("\(characteristic.uuid): properties contains .read")
peripheral.readValue(for: characteristic)
}
if characteristic.properties.contains(.notify) {
print("\(characteristic.uuid): properties contains .notify")
}
}
}
I am writing an app that needs to write a byte value to a CBPeripheral using iOS CoreBluetooth. I am able to read values, and the write is successful and triggers the didWriteValueFor delegate like it should. Basically, it does work, BUT, it takes a long time (about 3 seconds and reports of over 10). When I test the write process in another app (nRF Connect), the write is almost instantaneous. Here's the code I am using to write to the Characteristic:
func setConfigurationValue(_ i:UInt8){
guard peripheral != nil, configurationStateCharacteristic != nil else { return }
var vint:UInt8 = i
let intData = Data(bytes: &vint, count: MemoryLayout<UInt8>.size)
isWriting = true
peripheral?.writeValue(intData, for: configurationStateCharacteristic!, type: CBCharacteristicWriteType.withResponse)
// Notify any views that they should show a progress overlay
NotificationName.showProgressOverlay.post(userInfo: ["message":"Device configuring".localized], object: self)
}
Note, that peripheral is a stored reference to the CBPeripheral object, and configurationStateCharacteristic is a reference to the CBCharacteristic I am writing to. This code does work, but what is causing the peripheral BLE device to take so long in writing the data and sending a response?
Any ideas?
If i want to send data to a bluetooth module, which is connected to the Arduino, what code lines are specifically the ones I need to take notice of.
I want to send something like, the number '75' to the bluetooth module and the Arduino will read it
thanks
Bluetooth LE is very long and cumbersome with many delegates in between. The minimum path to write your data is:
Make sure you have bluetooth permission: CBCentralManagerDelegate.centralManagerDidUpdateStateand if so start scanning with scanForPeripherals
CBCentralManagerDelegate.didDiscover If this is the peripheral you want then set yourself as its delegate
CBPeripheralDelegate.peripheral:didDiscoverServices: If this is the service you want then stop scanning and discoverCharacteristics:for: service
CBPeripheralDelegate.peripheral:didDiscoverCharacteristicsFor: service If a characteristic in the array of characteristics is the one you want then:
func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
guard let characteristics = service.characteristics else {
return
}
for characteristic in characteristics {
if characteristic.uuid == CBUUID(string: characteristicIdentifier) {
let value: UInt8 = 75
let data = Data(bytes: [value])
peripheral.writeValue(data, for: characteristic, type: .withResponse)
}
}
}
I am trying to send some data from an iOS device to the HM-10 Bluetooth LE Module connected to an arduino. Problem is after connecting to the module discoverServices doesn't return a characteristic for the service.
func peripheral(peripheral: CBPeripheral, didDiscoverServices error: NSError?) {
if(error != nil) {
print(error?.description)
}
for service in peripheral.services! {
let thisService = service as CBService
print("Service: \(thisService.description)")
print("Characteristic: \(thisService.characteristics)")
}
}
This outputs:
Service: <CBService: 0x137e84ea0, isPrimary = YES, UUID = FFE0>
Characteristic: nil
I am a beginner with this arduino stuff as well as iOS. So any suggestions would be welcome. Maybe there is a way to write to the bluetooth module without knowing the characteristic... I have no idea.
I finally managed to get the answer. Because of my rudimentary understanding of the CoreBluetooth Framework I forgot to call discoverCharacteristics in didDiscoverServices. Well, I am really learning by doing. (I somehow thought discoverServices would call discoverCharacteristics itself.)