iOS 在 BLE 上写入数据时出现未知错误

Question

我正在尝试开发 iOS 应用程序，它正在检测 BLE 设备并需要调用写入命令。我可以成功连接到 BLE 设备并发现它的服务和特性。但是我在连接的外围设备上写入数据时遇到未知错误。下面是我写的代码：

发现的特征：

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error {
  NSArray *characteristics = [service characteristics];

  if (peripheral != self.peripheral) {
    NSLog(@"Wrong Peripheral.\n");
    return ;
  }

  if (error != nil) {
    NSLog(@"Error %@\n", error);
    return ;
  }

  for (CBCharacteristic *characteristic in characteristics) {

    if ([[characteristic UUID] isEqual:RWT_POSITION_CHAR_UUID]) {
      self.positionCharacteristic = characteristic;
    }
  }
}

这里是BLE设备写数据的函数

- (void)writeCommand{

    // See if characteristic has been discovered before writing to it
    if (!self.positionCharacteristic) {
        return;
    }
    NSString *cmd1=@"CQ+WHORU\r";

    NSData *dataToWrite = [cmd1 dataUsingEncoding:NSUTF8StringEncoding];

    CBCharacteristic *chr = self.positionCharacteristic;
    NSLog(@"%@,%lu...%@",chr.UUID,chr.properties,chr);

    NSInteger dataSize = [[NSByteCountFormatter stringFromByteCount:dataToWrite.length countStyle:NSByteCountFormatterCountStyleFile] integerValue];
    if (dataSize > 130) {
        NSLog(@"Cannot send more than 130 bytes");
    }
    else
    {
        [self.peripheral writeValue:dataToWrite forCharacteristic:self.positionCharacteristic type:CBCharacteristicWriteWithResponse];
    }
}

- (void)peripheral:(CBPeripheral *)peripheral
didWriteValueForCharacteristic:(CBCharacteristic *)characteristic
         error:(NSError *)error
{
    if (error)
    {
        NSLog(@"Error writing characteristic value: %@", [error localizedDescription]);
    }
    else
    {
        NSLog(@"Successfully writing characteristic value");
    }
}

在 "didWriteValueForCharacteristic" 委托方法中出现以下错误：

Error writing characteristic value: Unknown error.

此错误的可能原因是什么？

此外，如果我试图定义在 BLE 设备上发送数据的特性，例如：

CBMutableCharacteristic *writeChar = [[CBMutableCharacteristic alloc]initWithType:[CBUUID UUIDWithString:@"ffe1"] properties:CBCharacteristicPropertyWriteWithoutResponse|CBCharacteristicPropertyNotify value:nil permissions:CBAttributePermissionsWriteable|CBAttributePermissionsReadable];
int8_t cmd = *[cmd1 UTF8String];

NSData *data = [NSData dataWithBytes:&cmd length:sizeof(cmd)];

NSInteger dataSize = [[NSByteCountFormatter stringFromByteCount:dataToWrite.length countStyle:NSByteCountFormatterCountStyleFile] integerValue];
if (dataSize > 130) {
    NSLog(@"Cannot send more than 130 bytes");
}
else
{
    [self.peripheral writeValue:dataToWrite forCharacteristic:writeChar type:CBCharacteristicWriteWithResponse];
    //        [self.peripheral writeValue:dataToWrite forCharacteristic:writeChar type:CBCharacteristicWriteWithResponse];
}

然后我收到这个错误：

**CoreBluetooth[WARNING] CBMutableCharacteristic: 0x1552a270 UUID = Unknown (<ffe1>),Value = (null), Properties = 0x14, Permissions = 0x3, Descriptors = (null), SubscribedCentrals = (
)> is not a valid characteristic for peripheral <CBPeripheral: 0x15549930 identifier = FC71890D-9F71-5E16-086D-D491E1EF7599, Name = " DEMOBLE1", state = connected**

Answer 1

我在开发 iOS 应用程序（作为中央设备）和 BLE 设备固件（作为外围设备）时看到了这个错误。当我 changed/modified BLE 外设的特性时会发生这种情况。

iOS 似乎在连接后缓存有关服务和特征的信息。每当我将 build/download 新固件添加到设备时，我都可以通过更新外围设备的蓝牙地址来解决这个问题。

Answer 2

首先，您使用的是CBCentralManager，对吧？

确保您以正确的方式进行操作：

使用CBCentralManager

self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];

当外设连接时检测

- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{

    if (connectedDevice) // make sure you disconnect previous device
        [self.centralManager cancelPeripheralConnection:connectedDevice];

    connectedDevice = [peripheral retain];
    connectedDevice.delegate = self;
    [connectedDevice discoverServices:nil]; // this will discover all kind of services
}

如果连接过程中出现问题，您会在这里找到（例如，电池电量不足）

- (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{
    NSLog(@"Did fail to connect: %@",error.description);
    connectedDevice = nil;
}

成功连接的 BLE 出现问题（例如，电池电量低，用户关闭了设备）

- (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{
    NSLog(@"Disconnected: %@",error.description);
    connectedDevice = nil;
}

在这里，您可以找到可用的服务

- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI {
    NSLog([NSString stringWithFormat:@"%@",[advertisementData description]]);
}

6.

    - (void)centralManagerDidUpdateState:(CBCentralManager *)central{
        NSString *messtoshow;

        switch (central.state) {
            case CBCentralManagerStatePoweredOn:
            {
                [NSString stringWithFormat:@"Bluetooth is currently powered on and available to use."];

                CBUUID *heartRate = [CBUUID UUIDWithString:HRM_SERVICE_UUID];
                CBUUID *batteryLevel = [CBUUID UUIDWithString:BATTERY_LIFE_SERVICE_UUID];

                NSDictionary *scanOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:NO] forKey:CBCentralManagerScanOptionAllowDuplicatesKey];

                [self.centralManager scanForPeripheralsWithServices:[NSArray arrayWithObjects:heartRate,batteryLevel,nil] options:scanOptions];
                break;
            }

        }
    }

从现在开始，您可以实现CBPeripheralDelegate方法

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error
{
    for (CBService *service in peripheral.services) {
        NSLog(@"Discovered service: %@", service.UUID);
        [peripheral discoverCharacteristics:nil forService:service];
    }
}

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
{
    if ([service.UUID isEqual:[CBUUID UUIDWithString:HRM_SERVICE_UUID]])  {
        for (CBCharacteristic *aChar in service.characteristics)
        {
            if ([aChar.UUID isEqual:[CBUUID UUIDWithString:HRM_MEASUREMENT_CHARACTERISTIC_UUID]]) {
                [connectedDevice setNotifyValue:YES forCharacteristic:aChar];
            }
        }
    }

    if ([service.UUID isEqual:[CBUUID UUIDWithString:BATTERY_LIFE_SERVICE_UUID]])  {
        for (CBCharacteristic *aChar in service.characteristics)
        {
            if ([aChar.UUID isEqual:[CBUUID UUIDWithString:BATTERY_LEVEL_CHARACTERISTIC_UUID]]) {
                [connectedDevice readValueForCharacteristic:aChar];
            }
        }
    }
}

- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
    NSError* err = nil;
    if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:HRM_MEASUREMENT_CHARACTERISTIC_UUID]]) {
            NSData *data = [characteristic value];
    }

    if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:BATTERY_LEVEL_CHARACTERISTIC_UUID]]) { 

    }
}

这应该可以正常工作。我已经按照同样的方式实现了，没有任何问题。希望对您有所帮助。

Answer 3

当您写入数据时，您正在请求响应 (CBCharacteristicWriteWithResponse)。

如果您正在写入的特征没有设置属性 CBCharacteristicPropertyWrite，写入将失败，但只支持无响应写入（CBCharacteristicPropertyWriteWithoutResponse）。

if ((self.positionCharacteristic.properties & CBCharacteristicPropertyWrite) == CBCharacteristicPropertyWrite) {
    // Responses are available, so write with response.
    [self.peripheral writeValue:dataToWrite forCharacteristic:self.positionCharacteristic type:CBCharacteristicWriteWithResponse];
}
else if ((self.positionCharacteristic.properties & CBCharacteristicPropertyWriteWithoutResponse) == CBCharacteristicPropertyWriteWithoutResponse) {
    // Responses are not available.
    // Write with response is going to fail, so write without response.
    [self.peripheral writeValue:dataToWrite forCharacteristic:self.positionCharacteristic type:CBCharacteristicWriteWithoutResponse];
}

iOS 在 BLE 上写入数据时出现未知错误

Getting Unknown Error while writing data on BLE in iOS

ios

objective-c

iphone

bluetooth-lowenergy

core-bluetooth