Information Management

Overview

Payload devices with message subscription functionality can subscribe to the flight status data from the UAV, allowing users to implement a wide range of applications.

Basic Concepts

Message Subscription

Various components on the UAV produce a large amount of data in real-time according to the UAV's actual flight conditions. This data is pushed to other modules on the UAV. Users can use payload devices with message subscription functionality to specify the required data to subscribe to.

Subscription Process

After subscribing to a data item, the payload device can receive the subscribed information.

Subscription Items

Below is the list of data items that can be subscribed to using the PSDK message subscription functionality:

Note：

• If you need to search for subscription items in the code project, replace *_ with UAV_SUBSCRIPTION_TOPIC_, for example, *_QUATERNION becomes UAV_SUBSCRIPTION_TOPIC_QUATERNION.

Data Subscription TOPIC	EVO Max Series
Attitude Quaternion *_QUATERNION	Maximum frequency of 100Hz
Relative Ground Acceleration *_ACCELERATION_GROUND	Maximum frequency of 5Hz
Relative Body Acceleration *_ACCELERATION_BODY	Maximum frequency of 5Hz
Raw Acceleration *_ACCELERATION_RAW	Maximum frequency of 100Hz
Velocity *_VELOCITY	Maximum frequency of 100Hz
Fused Angular Rate *_ANGULAR_RATE_FUSIONED	Maximum frequency of 100Hz
Raw Angular Rate *_ANGULAR_RATE_RAW	Maximum frequency of 100Hz
Fused Altitude *_ALTITUDE_FUSED	Maximum frequency of 20Hz
Barometer Altitude *_ALTITUDE_BAROMETER	Maximum frequency of 5Hz
Home Point Altitude *_ALTITUDE_OF_HOMEPOINT	Maximum frequency of 10Hz
Fused Relative Ground Altitude *_HEIGHT_FUSION	Maximum frequency of 1Hz
Relative Ground Altitude *_HEIGHT_RELATIVE	Maximum frequency of 20Hz
Fused Position Coordinates *_POSITION_FUSED	Maximum frequency of 20Hz
GPS Date (YYYY-MM-DD) *_GPS_DATE	Maximum frequency of 10Hz
GPS Time (HH:MM:SS) *_GPS_TIME	Maximum frequency of 10Hz
GPS position *_GPS_POSITION	Maximum frequency of 10Hz
GPS velocity *_GPS_VELOCITY	Maximum frequency of 10Hz
GPS Information *_GPS_DETAILS	Maximum frequency of 10Hz
GPS Signal strength *_GPS_SIGNAL_LEVEL	Maximum frequency of 10Hz
RTK position *_RTK_POSITION	Maximum frequency of 10Hz
RTK velocity *_RTK_VELOCITY	Maximum frequency of 5Hz
RTK heading angle *_RTK_YAW	Maximum frequency of 5Hz
RTK position information *_RTK_POSITION_INFO	Maximum frequency of 10Hz
RTK heading information *_RTK_YAW_INFO	Maximum frequency of 5Hz
Compass information *_COMPASS	Maximum frequency of 5Hz
Remote control joystick information *_RC	Maximum frequency of 50Hz
Gimbal angles *_GIMBAL_ANGLES	Maximum frequency of 100Hz
Gimbal status *_GIMBAL_STATUS	Maximum frequency of 100Hz
Flight status *_STATUS_FLIGHT	Maximum frequency of 2Hz
Flight mode status *_STATUS_DISPLAYMODE	Maximum frequency of 2Hz
Motor startup error code *_STATUS_MOTOR_START_ERROR	Maximum frequency of 5Hz
Battery information *_BATTERY_INFO	Maximum frequency of 1Hz
Hardware clock synchronization *_HARD_SYNC	Maximum frequency of 10H0z
GPS control level *_GPS_CONTROL_LEVEL	Maximum frequency of 10Hz
Tagged remote control remote sensing information *_RC_WITH_FLAG_DATA	Maximum frequency of 50Hz
ESC data (Electronic Speed Controller data) *_ESC_DATA	Maximum frequency of 5Hz
Gimbal control mode *_GIMBAL_CONTROL_MODE	Control trigger
Cartesian coordinate position *_POSITION_VO	Maximum frequency of 100Hz
Obstacle avoidance data *_AVOID_DATA	Maximum frequency of 20Hz
Return home point setting status *_HOME_POINT_SET_STATUS	Maximum frequency of 1Hz
Return home point information *_HOME_POINT_INFO	Maximum frequency of 1Hz
1 Battery information of No. X *_BATTERY_SINGLE_INDEX1	Maximum frequency of 1Hz
2 Battery information of No. X *_BATTERY_SINGLE_INDEX2	Maximum frequency of 1Hz
Flight attitude information with timestamp *_IMU_ATTI_NAVI_WITH_TIMESTAMP	Maximum frequency of 20Hz

Using the Message Subscription Function

PSDK supports subscribing to the data pushed by the UAV using a callback registration method.

Message Subscription Module Initialization

For payload devices developed using PSDK, to subscribe to the status information of the UAV, the message subscription module must be initialized by calling the UAV_Subscription_Init() function.

uavStat = UAV_Subscription_Init();
if (uavStat != UAV_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
    USER_LOG_ERROR("init data subscription module error.");
    return UAV_ERROR_SYSTEM_MODULE_CODE_UNKNOWN;
}

uavStat = UAV_Subscribe_Topic(UAV_SUBSCRIPTION_TOPIC_QUATERNION, UAV_DATA_SUBSCRIPTION_TOPIC_1_HZ,
                                               UAV_FcSubscription_ReceiveQuaternionCallback);
    if (uavStat != UAV_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
        UAV_LOG_ERROR("Subscribe topic quaternion info error.");
        return UAV_ERROR_SYSTEM_MODULE_CODE_UNKNOWN;
    } else {
        UAV_LOG_INFO("Subscribe topic quaternion info success.");
    }

Constructing a Callback Function to Receive Information from the UAV

• Constructing the Callback Function
  The callback function is constructed to receive the information pushed from the UAV.

  Note：

  • To avoid memory corruption, the data address must be type-cast to the pointer type defined in the subscription item data structure.

static T_UAVReturnCode UAV_FcSubscription_ReceiveQuaternionCallback(const uint8_t *data, uint16_t dataSize)
{
    T_UAVSubscriptionQuaternion *quaternion = (T_UAVSubscriptionQuaternion *) data;
    double pitch, yaw, roll;

    USER_UTIL_UNUSED(dataSize);

    pitch = (double) asinf(-2 * quaternion->q1 * quaternion->q3 + 2 * quaternion->q0 * quaternion->q2) * 57.3;
    roll = (double) atan2f(2 * quaternion->q2 * quaternion->q3 + 2 * quaternion->q0 * quaternion->q1, -2 * quaternion->q1 * quaternion->q1 - 2 * quaternion->q2 * quaternion->q2 + 1) * 57.3;
    yaw = (double) atan2f(2 * quaternion->q1 * quaternion->q2 + 2 * quaternion->q0 * quaternion->q3, -2 * quaternion->q2 * quaternion->q2 - 2 * quaternion->q3 * quaternion->q3 + 1) * 57.3;

    if (s_userFcSubscriptionDataShow == true) {
        USER_LOG_INFO("receive quaternion data.");

        USER_LOG_INFO("quaternion: %f %f %f %f.\r\n", quaternion->q0, quaternion->q1, quaternion->q2, quaternion->q3);
        USER_LOG_INFO("euler angles: pitch = %.2f roll = %.2f yaw = %.2f.", pitch, yaw, roll);
        UAV_Test_WidgetLogAppend("pitch = %.2f roll = %.2f yaw = %.2f.", pitch, yaw, roll);
    }

    return UAV_ERROR_SYSTEM_MODULE_CODE_SUCCESS;
}