iOS:Send Command To peripheral and Receive response From it

Question

I am developing core bluetooth app in iOS. I have smartwatch device and is connecting to the app I have developed and aim able to discover the service and characteristics from it and when I am trying to read the information from the watch aim getting errors as below

 Bluetooth_iph[2688:614669] Did discover peripheral. peripheral: <CBPeripheral: 0x17daf4d0,   
  identifier = D675EA0B-1342-0C74-9D3D-98CAFA478985, name = BLEDEVICE, state = connecting> 
   rssi: -51, UUID: <CFUUID 0x17d96e80> D675EA0B-1342-0C74-9D3D-98CAFA478985     
  advertisementData: {
kCBAdvDataIsConnectable = 1;
kCBAdvDataLocalName = "BLEDEVICE";
kCBAdvDataServiceUUIDs =     (
    8880
);
kCBAdvDataTxPowerLevel = 7;

  } 
 2014-10-17 10:06:13.695 Bluetooth_iph[2688:614669] WARNING: No service found
 2014-10-17 10:06:18.353 Bluetooth_iph[2688:614669] Peripheral Connected
 2014-10-17 10:06:18.354 Bluetooth_iph[2688:614669]  started  time is 10:06:10 17-10-14
 2014-10-17 10:06:18.354 Bluetooth_iph[2688:614669] Scanning stopped
 2014-10-17 10:06:18.485 Bluetooth_iph[2688:614669] Found a Device Manufacturer Name 
 2014-10-17 10:06:18.541 Bluetooth_iph[2688:614669] Error updating value for characteristic   
 8881 error: Reading is not permitted.

 2014-10-17 10:06:18.601 Bluetooth_iph[2688:614669] Error updating value for characteristic 
 8881 error: Reading is not permitted.

 2014-10-17 10:06:18.662 Bluetooth_iph[2688:614669] Error updating value for characteristic 
 8881 error: Reading is not permitted.

And for discovering the characteristics for the service I have written as below.

    - (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:
  (CBService   
 *)service error:(NSError *)error

  {
  if (error)
  {
    NSLog(@"Discovered characteristics for %@ with error: %@", service.UUID, [error 
     localizedDescription]);
    return;
  }


   if([service.UUID isEqual:[CBUUID UUIDWithString:@"8880"]])
  {
    for (CBCharacteristic * characteristic in service.characteristics)
    {
        /* Read manufacturer name */
        if([characteristic.UUID isEqual:[CBUUID UUIDWithString:@"8881"]])
        {
            [_discoveredPeripheral readValueForCharacteristic:characteristic];
            NSLog(@"Found a Device Manufacturer Name Characteristic - Read manufacturer 
      name");
        }
    }
  }

   if ( [service.UUID isEqual:[CBUUID UUIDWithString:CBUUIDGenericAccessProfileString]] )
    {
    for (CBCharacteristic *characteristic in service.characteristics)
    {
        /* Read device name */
        if([characteristic.UUID isEqual:[CBUUID UUIDWithString:CBUUIDDeviceNameString]])
        {
            [_discoveredPeripheral readValueForCharacteristic:characteristic];
            NSLog(@"Found a Device Name Characteristic - Read device name");
        }
     }
  }
  }

And for update value for characteristic

 - (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:  
  (CBCharacteristic *)characteristic error:(NSError *)error
 {
 if (error)
  {
     NSLog(@"Error updating value for characteristic %@ error: %@", characteristic.UUID,   
   [error localizedDescription]);
    return;
  }
}

As aim new to iOS development my requirement is I have to give some request to ble device so it should respond and that response I should get in the iOS app. Above code is on behalf of my knowledge. please help me if possible by code or any other examples.

Answer 1

You should check the properties property of the CBCharacteristic - It will tell you what you can do with the characteristic. From the message you are getting reading is not supported on this characteristic - Either you can only write to it or, if it is meant to send information to your central, then you probably have to do it using notification or indication ( CBCharacteristicPropertyNotify and/or CBCharacteristicPropertyIndicate set in properties ).

If this is the case then you need to use [peripheral setNotifyValue:YES forCharacteristic:characteristic]; When the device has new data for this characteristic it will call the peripheral:didUpdateNotificationStateForCharacteristic:error: delegate method.