当遥控器和无人机无法匹配时就需要进行遥控器对频。DJIRemoteController 中提供了遥控器对频的相关接口。

开始对频和停止对频

在进行对频前需要先调用isMultiDevicePairingSupported 方法判断遥控器是否支持多设备对频，多设备对频就是同时支持无人机对频和 RTK 基站对频。如果方法返回 NO , 则可以使用下面方法进行对频和停止对频：

  1. - (void)startPairingWithCompletion:(DJICompletionBlock)completion;
  3. - (void)stopPairingWithCompletion:(DJICompletionBlock)completion;

如果返回 YES ,则使用下面的方法：

  1. - (void)startMultiDevicePairingWithTarget:(DJIRCPairingDevice)target
  2.                            withCompletion:(DJICompletionBlock)completion;
  4. - (void)stopMultiDevicePairingWithCompletion:(DJICompletionBlock)completion;

DJIRCPairingDevice 定义了多设备对频的设备类型：

  1. typedef NS_ENUM (uint8_t, DJIRCPairingDevice){
  3.     /**
  4.      *  The device to be paired with is an aircraft.
  5.      */
  6.     DJIRCPairingDeviceAircraft,
  9.     /**
  10.      *  The device to be paired with is an RTK base station.
  11.      */
  12.     DJIRCPairingDeviceRTKBaseStation,
  15.     /**
  16.      *  Unknown.
  17.      */
  18.     DJIRCPairingDeviceUnknown = 0xFF,
  19. };

获取对频状态

在对频的过程中，需要获取到对频的状态，我们可以通过 KeyManager 监听状态。 DJIRemoteControllerKey 中提供了 DJIRemoteControllerParamPairingState
和 DJIRemoteControllerParamMultiDevicePairingState。

不过测试发现可以通过 DJIRemoteControllerParamPairingState 来获取单设备的对频状态，但是无法通过 DJIRemoteControllerParamMultiDevicePairingState 来获取多设备的对频状态，不过我们可以通过 DJIRemoteControllerDelegate 中的 

  1. - (void)remoteController:(DJIRemoteController *)rc didUpdateMultiDevicePairingState:(DJIRCMultiDeviceAggregationState *)state;

代理方法，获取多设备对频的状态。

DJIRCMultiDeviceAggregationState 中定义了无人机和 RTK 基站的对频状态：

  1. @interface DJIRCMultiDeviceAggregationState : NSObject
  4. /**
  5.  *  The device state of aircraft.
  6.  */
  7. @property (nonatomic, readonly) DJIRCMultiDeviceState aircraftState;
  10. /**
  11.  *  The device state of RTK base station.
  12.  */
  13. @property (nonatomic, readonly) DJIRCMultiDeviceState RTKBaseStationState;
  15. @end

aircraftState 和 RTKBaseStationState 都是 DJIRCMultiDeviceState 类型，其定义如下：

  1. typedef NS_ENUM(uint8_t, DJIRCMultiDeviceState) {
  3.     /**
  4.      *  The remote controller is unpaired with the device. This state is for both
  5.      *  aircraft and base station.
  6.      */
  7.     DJIRCMultiDeviceStateUnpaired = 0,
  9.     /**
  10.      *  The remote controller is pairing with the device. This state is only for
  11.      *  aircraft.
  12.      */
  13.     DJIRCMultiDeviceStatePairing,
  15.     /**
  16.      *  The remote controller is paired. This state is only for aircraft.
  17.      */
  18.     DJIRCMultiDeviceStatePaired,
  21.     /**
  22.      *  The remote controller is paired with the device but the connection between the
  23.      *  device  and the remote  controller is broken. The remote controller already
  24.      *  remembers the device and the connection will receover  automatically when it is
  25.      *  possible. This state is only for base station. Only Supported by Phantom 4 RTK.
  26.      */
  27.     DJIRCMultiDeviceStateDisconnected,
  30.     /**
  31.      *  The remote controller is paired with the device and it is connected to the
  32.      *  device.  This state is only for base station.
  33.      */
  34.     DJIRCMultiDeviceStateConnected,
  37.     /**
  38.      *  Unknown.
  39.      */
  40.     DJIRCMultiDeviceStateUnknown = 0xFF,
  41. };

当我们使用 startMultiDevicePairingWithTarget:withCompletion: 进行 RTK 基站对频时，如果 RTKBaseStationState 的值是 DJIRCMultiDeviceStateConnected 则表示对频成功；当我们与飞机对频时，如果 aircraftState 的值是 DJIRCMultiDeviceStatePaired 则表示对频成功。