蓝牙读取信息过程：连接-查询服务-发现服务、搜索该服务包含的特征值-发现特征值-读取特征值（读取所需外设信息，包含major、minor、rssi、电量等等）

蓝牙外设类CBPeripheral （代码中的所有特征值UUID均向硬件厂商获取）

@property (strong, nonatomic) CBPeripheral *beaconPeripheral; 
 self.beaconServiceUUID = [CBUUID UUIDWithString:@"xxxxxxxxxxx"]; //服务UUID需要找硬件厂商获取

连接代码

 self.beaconPeripheral.delegate = self;
  [self.bluetoothManager connectPeripheral:self.beaconPeripheral options:nil];

连接代理-CBCentralManagerDelegate

-(void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{
    NSLog(@"蓝牙连接成功 %@",peripheral.name);
    [self.beaconPeripheral discoverServices:[NSArray arrayWithObject:self.beaconServiceUUID]];//连接成功后查询beacon服务
}
-(void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error
{
    NSLog(@"蓝牙断开连接 %@",peripheral.name);
}
-(void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error
{
    NSLog(@"连接失败 %@",peripheral.name);
}

发现beacon服务代理--CBPeripheralDelegate

-(void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error
{
    for(CBService *service in peripheral.services)
    {
        if ([service.UUID isEqual:self.beaconServiceUUID]) {
            //发现服务，搜索特征值
            [self.beaconPeripheral discoverCharacteristics:nil forService:service];
        }
    }
}
-(void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
{
    if ([service.UUID isEqual:self.beaconServiceUUID]) {
        for(CBCharacteristic *characteristic in service.characteristics)
        {
           //majorminor值
            if ([characteristic.UUID isEqual:self.majorMinorCharacteristicUUID]) {
                self.majorMinorCharacteristic = characteristic;
                [self.beaconPeripheral readValueForCharacteristic:characteristic];//读取
            }
            if ([characteristic.UUID isEqual:self.rssiCharacteristicUUID]) {
                self.rssiCharacteristic = characteristic;
                [self.beaconPeripheral readValueForCharacteristic:characteristic];
            }
        }
    }
}
//获取特征值value
-(void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
    if ([characteristic.UUID isEqual:self.majorMinorCharacteristicUUID]) {
        NSString *major = [NSString stringWithFormat:@"%hu",[self decodeMajor:characteristic.value]];
        NSString *minor = [NSString stringWithFormat:@"%hu",[self decodeMinor:characteristic.value]];
    }
    else if ([characteristic.UUID isEqual:self.rssiCharacteristicUUID]) {
        NSString *rssi = [NSString stringWithFormat:@"%hhd",[self decodeRSSI:characteristic.value]];
   }
}

写入操作

写入major、minor

  uint16_t major = (uint16_t)majorVlue;
  uint16_t minor = (uint16_t)minorValue;
  uint8_t majorMinor[4];
  majorMinor[0] = ((major >> 8) & 0xFF);
  majorMinor[1] = (major & 0xFF);
  majorMinor[2] = ((minor >> 8) & 0xFF);
  majorMinor[3] = (minor & 0xFF);
  NSData *data = [NSData dataWithBytes:majorMinor length:4];
  [self.beaconPeripheral writeValue:data forCharacteristic:self.majorMinorCharacteristic type:CBCharacteristicWriteWithResponse];

写入rssi

 int8_t rssi = (int8_t)rssiValue;
    NSLog(@"rssi before save: %hhd",rssi);
    NSData *data = [NSData dataWithBytes:&rssi length:1];
    [self.beaconPeripheral writeValue:data forCharacteristic:self.rssiCharacteristic type:CBCharacteristicWriteWithResponse];

写入回调

-(void)peripheral:(CBPeripheral *)peripheral didWriteValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
     //如果写入成功，再读取一次，进入didUpdateValueForCharacteristic回调，刷新数据
      [self.beaconPeripheral readValueForCharacteristic:characteristic];
}