didUpdateValueForCharacteristic(setNotifyValue:YES) doesn't work

Question

I want to receive notifications when values change. I am following this tutorial -> Introduction to Core Bluetooth: Building a Heart Rate Monitor

I use this Bluetooth device -> IC card Reader (Sony product)

- (void)viewDidLoad {
    [super viewDidLoad];
    _myCentralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];
    [_myCentralManager scanForPeripheralsWithServices:nil options:nil];
    self.myCentralManager = _myCentralManager;
}

#pragma mark - CBCentralManagerDelegate

// method called whenever you have successfully connected to the BLE peripheral
- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{
    [peripheral setDelegate:self];
    [peripheral discoverServices:nil];
    NSString *connected = [NSString stringWithFormat:@"Connected: %@", peripheral.state == CBPeripheralStateConnected ? @"YES" : @"NO"];
    NSLog(@"%@", connected);
}

// CBCentralManagerDelegate - This is called with the CBPeripheral class as its main input parameter. This contains most of the information there is to know about a BLE peripheral.
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI{
    NSLog(@"Discovered %@", _peripheral.name);
    NSString *localName = [advertisementData objectForKey:CBAdvertisementDataLocalNameKey];

    if ([localName length] > 0) {
        NSLog(@"Found the : %@", localName);
      //  [self.myCentralManager stopScan];
        self.peripheral = peripheral;
        peripheral.delegate = self;
        [self.myCentralManager connectPeripheral:peripheral options:nil];
    }
}

// method called whenever the device state changes.
- (void)centralManagerDidUpdateState:(CBCentralManager *)central{
    // Determine the state of the peripheral
    if ([central state] == CBCentralManagerStatePoweredOff) {
        NSLog(@"CoreBluetooth BLE hardware is powered off");
    }
    else if ([central state] == CBCentralManagerStatePoweredOn) {
        NSLog(@"CoreBluetooth BLE hardware is powered on and ready");
    }
    else if ([central state] == CBCentralManagerStateUnauthorized) {
        NSLog(@"CoreBluetooth BLE state is unauthorized");
    }
    else if ([central state] == CBCentralManagerStateUnknown) {
        NSLog(@"CoreBluetooth BLE state is unknown");
    }
    else if ([central state] == CBCentralManagerStateUnsupported) {
        NSLog(@"CoreBluetooth BLE hardware is unsupported on this platform");
    }
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
}

#pragma mark - CBPeripheralDelegate

// CBPeripheralDelegate - Invoked when you discover the peripheral's available services.
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error{
    for (CBService *service in peripheral.services) {
        NSLog(@"Discovered service: %@", service.UUID);
        [peripheral discoverCharacteristics:nil forService:service];
    }
}

// Invoked when you discover the characteristics of a specified service.
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error{
    // Deal with errors (if any)
    if (error) {
        NSLog(@"Error discovering characteristics: %@", [error localizedDescription]);
        return;
    }

    // Again, we loop through the array, just in case.
    for (CBCharacteristic *characteristic in service.characteristics) {

        [peripheral setNotifyValue:YES forCharacteristic:characteristic];
    }

    for (CBCharacteristic *aChar in service.characteristics)
    {
        [_peripheral setNotifyValue:YES forCharacteristic:aChar];
        NSLog(@"Found characteristic : %@ UUID : %@",aChar.value,aChar.UUID);
        NSString *value = [[NSString alloc] initWithData:aChar.value encoding:NSUTF8StringEncoding];
        NSLog(@"Value %@",value);
    }
}

// Invoked when you retrieve a specified characteristic's value, or when the peripheral device notifies your app that the characteristic's value has changed.
- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{
    if (error) {
        NSLog(@"Error reading characteristics: %@", [error localizedDescription]);
        return;
    }

    if (characteristic.value != nil) {
        //value here.
    }

    NSLog(@"Characteristic value : %@ with ID %@", characteristic.value, characteristic.UUID);
    //[delegate characteristicValueRead:characteristic.value];
    NSLog(@"Caaled characteristic: %@",characteristic.value);
     [self getHeartBPMData:characteristic error:error];
    // Add your constructed device information to your UITextView
}

And console Log is:

> 2014-03-23 21:37:37.215 CBTutorial[2736:60b] CoreBluetooth[WARNING] <CBCentralManager: 0x1455dec0> is not powered on
2014-03-23 21:37:37.253 CBTutorial[2736:60b] CoreBluetooth BLE hardware is powered on and ready
2014-03-23 21:37:37.257 CBTutorial[2736:60b] Discovered (null)
2014-03-23 21:37:37.261 CBTutorial[2736:60b] Discovered (null)
2014-03-23 21:37:37.263 CBTutorial[2736:60b] Found the : PaSoRi
2014-03-23 21:37:37.493 CBTutorial[2736:60b] Connected: YES
2014-03-23 21:37:37.726 CBTutorial[2736:60b] Discovered service: Unknown (<233e8100 3a1b1c59 9bee1803 73dd03a1>)
2014-03-23 21:37:37.728 CBTutorial[2736:60b] Discovered service: Device Information
2014-03-23 21:37:37.732 CBTutorial[2736:60b] Found characteristic : <0000ffff ff0200fe d7131600> UUID : Unknown (<233e8101 3a1b1c59 9bee1803 73dd03a1>)
2014-03-23 21:37:37.733 CBTutorial[2736:60b] Value (null)
2014-03-23 21:37:37.735 CBTutorial[2736:60b] Found characteristic : <000000> UUID : Unknown (<233e8102 3a1b1c59 9bee1803 73dd03a1>)
2014-03-23 21:37:37.736 CBTutorial[2736:60b] Value 
2014-03-23 21:37:37.738 CBTutorial[2736:60b] Found characteristic : <0000ff00 ff00> UUID : Unknown (<233e8103 3a1b1c59 9bee1803 73dd03a1>)
2014-03-23 21:37:37.739 CBTutorial[2736:60b] Value (null)
2014-03-23 21:37:37.742 CBTutorial[2736:60b] Found characteristic : <> UUID : Unknown (<233e8104 3a1b1c59 9bee1803 73dd03a1>)
2014-03-23 21:37:37.744 CBTutorial[2736:60b] Value 
2014-03-23 21:37:37.746 CBTutorial[2736:60b] Found characteristic : <> UUID : Unknown (<233e8105 3a1b1c59 9bee1803 73dd03a1>)
2014-03-23 21:37:37.747 CBTutorial[2736:60b] Value 
2014-03-23 21:37:37.749 CBTutorial[2736:60b] Found characteristic : <> UUID : Unknown (<233e8106 3a1b1c59 9bee1803 73dd03a1>)
2014-03-23 21:37:37.750 CBTutorial[2736:60b] Value 
2014-03-23 21:37:37.752 CBTutorial[2736:60b] Found characteristic : <> UUID : Unknown (<233e8107 3a1b1c59 9bee1803 73dd03a1>)
2014-03-23 21:37:37.753 CBTutorial[2736:60b] Value 
2014-03-23 21:37:37.756 CBTutorial[2736:60b] Found characteristic : <41697250 61536f52 69> UUID : Manufacturer Name String
2014-03-23 21:37:37.758 CBTutorial[2736:60b] Value AirPaSoRi
2014-03-23 21:37:37.760 CBTutorial[2736:60b] Found characteristic : <4d6f6465 6c4e756d 62657230 31> UUID : Model Number String
2014-03-23 21:37:37.762 CBTutorial[2736:60b] Value ModelNumber01
2014-03-23 21:37:37.764 CBTutorial[2736:60b] Found characteristic : <4669726d 77617265 3031> UUID : Firmware Revision String
2014-03-23 21:37:37.765 CBTutorial[2736:60b] Value Firmware01
2014-03-23 21:37:37.767 CBTutorial[2736:60b] Found characteristic : <536f6674 77617265 3031> UUID : Software Revision String
2014-03-23 21:37:37.768 CBTutorial[2736:60b] Value Software01

Why I can't receive didUpdateValueForCharacteristic(Even setNotifyValue:YES) callbacks? (I Already tried to touch to IC card) Please help me.

Answer 1

First of all.

In your code, you are calling:

_myCentralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];
[_myCentralManager scanForPeripheralsWithServices:nil options:nil];

in viewDidLoad. this is a mistake. You should call scanForPeripheralsWithServices:options: into centralManagerDidUpdateState: and only in the scenario where state == CBCentralManagerStatePoweredOn

Second:

It is a good practice to assign your discovered peripheral to a retained CBPeripheral into centralManager: didConnectPeripheral: like:

self.myPeripheral = peripheral;
self.myPeripheral.delegate = self;

Third

peripheral: didUpdateValueForCharacteristic: error: is invoked by:

• readValueForCharacteristic:
• setNotifyValue: forCharacteristic

It is really weird why readValueForCharacteristic: is not invoking peripheral: didUpdateValueForCharacteristic: error:, also maybe there is some extra problem.

Can you try to call setNotifyValue: forCharacteristic and see what happen?

BTW, the best CoreBluetooth tutorial is the Apple Core Bluetooth Programming Guide

Answer 2

First you need to write proper command to firmware then it will send you respective response. once you got response from firmware didUpdateValueForCharacteristic method will get called. In case writing is not happening properly you will not get any response therefor this method will not get called.

Mostly we will send the command as hexadecimal.