iOS从BLE设备读取数据

Question

我正在尝试从 BLE 设备读取数据，但不断收到权限错误。 演示项目可以在这里找到： https : //github.com/sergiomtzlosa/CoreBluetooth-Demo （请记住 - 我的代码与这个有点不同）。

连接和读取值一般没有问题，但有一些特性（这是必不可少的）会导致权限错误。

控制台日志：更新错误！！！ 特征：“未知 (< fff4 >)”，错误： “不允许读取”。

因此，当我从该特征订阅或读取数据时，它每次都会向我发送 NULL（可能的原因：没有读取权限）。

控制台日志：特征：“未知（< fff4 >）”-> 值：（空）

这是一个代码段：

//Action on discovering services
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error
{

if (error) 
{
    NSLog(@"Discovered services for %@ with error: %@", peripheral.name, [error localizedDescription]);
    return;
}
for (CBService *service in peripheral.services) {

    NSLog(@"Discovereddddddddddd service %@", service.UUID);
    [testPeripheral discoverCharacteristics:nil  forService:service];
}
 NSLog(@"didDiscoverServicesEnd");
}

//Action on discovered characteristics
- (void)peripheral:(CBPeripheral *)peripheral
didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error {
NSLog(@"didDiscoverCharacteristicsForService!");
for (CBCharacteristic *characteristic in service.characteristics) {
    NSLog(@"Discovered characteristic %@", characteristic.UUID);
    NSLog(@"---------------------------------------------------");
    NSLog(@"Reading value for characteristic %@", characteristic.UUID);
    [peripheral readValueForCharacteristic:characteristic];
    NSLog(@"+++++++++++++++++++++++++++++++++++++++++++++++++++");
    [peripheral setNotifyValue:YES forCharacteristic:characteristic];
    }
}

//Action on reading value
- (void)peripheral:(CBPeripheral *)peripheral 
didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{
if (error){
    NSLog(@"Update error!!! Characteristic: %@ with error: %@", characteristic.UUID, [error localizedDescription]);
    return;
}else{
    NSData *data = characteristic.value;
    NSString *str = [NSString stringWithUTF8String:[data bytes]];
    NSLog(@"Characteristic: %@ -> with value: %@", characteristic.UUID, str);
}
}

怎么了？ 有没有办法克服这个问题？

Answer 1

外围设备是嵌入式设备还是另一个 iOS 设备。 我已经看到必须明确配置外围设备的特性以具有读取权限的地方。 仅仅因为您发现了一个特征并不意味着您可以阅读它。

Answer 2

您必须检查您是否有权访问该值，该权限是在您初始化 CBCharacteristic 时设置的

“特征值权限值表示特征值的读取、写入和加密权限。

typedef enum {
   CBAttributePermissionsReadable = 0x01,
   CBAttributePermissionsWriteable = 0x02,
   CBAttributePermissionsReadEncryptionRequired = 0x04,
   CBAttributePermissionsWriteEncryptionRequired = 0x08,
} CBAttributePermissions;"

https://developer.apple.com/library/ios/documentation/CoreBluetooth/Reference/CBMutableCharacteristic_Class/Reference/CBMutableCharacteristic.html