I have successfully connected to BLE devices using the same code, but this device is not letting me subscribe. It's frustrating because I cannot figure out how to get a meaningful error message.
There is a Read/Notify/Indicate characteristic that I am attempting to listen to. The code I send is:
peripheral.setNotifyValue(true, for: characteristic)
my listener is:
func peripheral(_ peripheral: CBPeripheral, didUpdateNotificationStateFor characteristic: CBCharacteristic, error: Error?) {
if ((error) != nil) {
NSLog("Error changing notification state: " + error!.localizedDescription)
}
if characteristic.isNotifying {
NSLog("Notification Updated")
}
}
The error I get is:
Error changing notification state: Unknown ATT error.
I have downloaded another app that interfaces with this device successfully, so I know that the hardware is functioning properly.
I don't know if there is some sort of encryption or other setting that needs to be sent to allow communication with this device. Any advice would be appreciated.
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'm experimenting with the CoreBluetooth Framework for iOS and I'm facing an issue that I find very Strange.
Once I have a Connected Peripheral, I want to discover it's services - but it fails. Despite searching for and finding Peripherals which offer a specific service. See the code below:
func centralManagerDidUpdateState(central: CBCentralManager) {
if(central.state != .PoweredOn) {
print("Returning due to wrong state: ", central.state)
return;
}
print("Starting peripheral scan")
manager.scanForPeripheralsWithServices(serviceUUID, options: nil)
}
Peripheral Scanning is started and looking for specified serviceUUIDs. In this case: serviceUUIDs = [CBUUID(string: "13333333-3333-3333-3333-333333333337")]. If I change the String, No service is discovered at all (as expected).
func centralManager(central: CBCentralManager, didDiscoverPeripheral peripheral: CBPeripheral, advertisementData: [String : AnyObject], RSSI: NSNumber) {
print("Discovered peripheral: ", peripheral.name)
if(peripheral.name == "PizzaSquat") {
print("Advertising data: ", advertisementData)
print("RSSI: ", RSSI)
activePeripheral = peripheral
print("Connecting to peripheral")
manager.connectPeripheral(peripheral, options: nil)
}
}
On a Linux computer, I have a Bleno instance running which is displaying as a Peripheral with the name "PizzaSquat" (And obviously offers a Service, since it's discovered at all. So when this Peripheral is discovered, I connect to it.
func centralManager(central: CBCentralManager, didConnectPeripheral peripheral: CBPeripheral) {
print("Connected to Peripheral: ", peripheral.name)
if(peripheral.services == nil) {
print("Starting service discovery")
peripheral.delegate = self
peripheral.discoverServices(serviceUUIDs)
} else {
print("Already has services: ")
for service: CBService in peripheral.services! {
print(service)
}
}
}
Once connected (to "PizzaSquat"), I check if it already has services (It doesn't) and start Service discovery. Everything is correct up to this point - But no Services are ever discovered. I expect the below function to be called:
func peripheral(peripheral: CBPeripheral, didDiscoverServices error: NSError?) {
print("Discovered new Service")
for service: CBService in peripheral.services! {
print(service)
}
}
with at least one service, Since the Peripheral shouldn't be discovered at all if it didn't have the specified Service!
I have also tried to call peripheral.discoverServices(nil) to discovery any Service, but still no response.
Could someone help me find the problem?
When you scan for CBPeripheral objects, the peripheral service UUID is obtained from the advertisement packet. The peripheral is basically saying, "Oh yeah, I have this service UUID!" iOS picks that up and passes the CBPeripheral to you.
But the peripheral might not be synced with what is in the advertisement packet. It's a non-binding agreement that the advertisement packet matches what's actually in the peripheral's service/characteristic hierarchy.
So what this means is that it's possible for a peripheral to advertise one service UUID, but actually contain another (or none).
Check out LightBlue on iOS or nRF Control Panel on Android to see if the service/characteristic hierarchy matches what you think it does. In LightBlue you should be able to view the advertisement data and compare it to the services on the peripheral you're connected to.
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.)
I'm developing an app for OS X (10.10) and iOS 8 to exchange some messages with a BLE peripheral. I want my app to find and connect to the peripheral, to send the message to it, and lastly to disconnect, so that the peripheral is free to be accessed from some other device. Everything works fine except for the following particular but still important situation: I scan for BLE devices and I find my device but still I don't connect to it because I have no messages to send. Then I walk away (out of range) or simply I turn the peripheral off. I still have saved in a var my CBPeripheral and I try to connect to it. Nothing happens while I would like the method centralManager:didFailToConnectPeripheral:error: to be called so that I can start to scan again.
centralManager:didConnectPeripheral working properly.
The documentation tells that bluetooth connection requests don't time out so I was wondering what other kinds of problems could lead to a connection failure
func connect(){
if let peripheral = self.peripheralBLE { //Check if the CBPeripheral I was looking for is properly stored
centralManager!.connectPeripheral(peripheral, options: nil)
}
else {
println("Nothing to connect"); //Didn't find any peripheral
}
}
func centralManager(central: CBCentralManager!, didConnectPeripheral peripheral: CBPeripheral!) {
print("connected");
println(peripheral.name);
if (peripheral == nil) {
return;
}
// Create new service class
if (peripheral == self.peripheralBLE) { //if it is the peripheral I was looking for then initialize the service for communication
self.bleService = RFduino(initWithPeripheral: peripheral)
}
connectionStatus = .connected; //update connection status
// Stop scanning for new devices
central.stopScan()
}
func centralManager(central: CBCentralManager!, didFailToConnectPeripheral peripheral: CBPeripheral!, error: NSError!) {
println("Failed to connect peripheral");
if peripheral == self.peripheralBLE{
self.bleService = nil;
self.peripheralBLE = nil;
self.connectionStatus = .disconnected;
}
self.startScanning();
}