dji开发之获取订阅

当选择的平台是Linux时，应该如何获取无人机的传感器信息呢？

大疆OnBoard SDK提供了两种方式（广播和订阅），这里讲如何订阅无人机传感器数据：

初始化订阅后，通过TopicName topicList50Hz[] = {}添加需要订阅的话题。

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// Telemetry: Verify the subscription
int responseTimeout = 1;
ACK::ErrorCode subscribeStatus;
subscribeStatus = vehicle->subscribe->verify(responseTimeout);
if (ACK::getError(subscribeStatus) != ACK::SUCCESS)
{
  ACK::getErrorCodeMessage(subscribeStatus, __func__);
  return false;
}
    // Telemetry: Subscribe to quaternion, fused lat/lon and altitude at freq 50 Hz
int       pkgIndex        = 2;
int       freq            = 50;
TopicName topicList50Hz[] = {TOPIC_QUATERNION, TOPIC_GIMBAL_ANGLES, TOPIC_GPS_FUSED, TOPIC_RC };
int       numTopic = sizeof(topicList50Hz) / sizeof(topicList50Hz[0]);
bool      enableTimestamp = false;

bool pkgStatus = vehicle->subscribe->initPackageFromTopicList(
  pkgIndex, numTopic, topicList50Hz, enableTimestamp, freq);
if (!(pkgStatus))
{
  return pkgStatus;
}
subscribeStatus =
  vehicle->subscribe->startPackage(pkgIndex, responseTimeout);
if (ACK::getError(subscribeStatus) != ACK::SUCCESS)
{
  ACK::getErrorCodeMessage(subscribeStatus, __func__);
  // Cleanup before return
  vehicle->subscribe->removePackage(pkgIndex, responseTimeout);
  return false;

这里以TOPIC_GIMBAL_ANGLES话题为例。

当订阅了该话题后获取话题的数据：

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TypeMap<TOPIC_GIMBAL_ANGLES>::type subscriptionGimbal;
subscriptionGimbal = vehicle->subscribe->getValue<TOPIC_GIMBAL_ANGLES>();

如何知道subscriptionGimbal包含哪些数据呢？下面是大疆官方提供对各种订阅话题的说明，可以找到对应的模块：

DJI Onboard SDK: Telemetry Topics

djiTopic

于是便可正常获取传感器的具体数据了：

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std::cout<<"Gimbal pitch:" << subscriptionGimbal.x << std::endl;
std::cout<<"Gimbal roll:" << subscriptionGimbal.y << std::endl;
std::cout<<"Gimbal yaw:" << subscriptionGimbal.z << std::endl;