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	Autel Alpha Series
Attitude Quaternion *_QUATERNION	Up to 5 Hz	Up to 5 Hz
Ground-relative Acceleration *_ACCELERATION_GROUND	Up to 1 Hz	Up to 1 Hz
Body-relative Acceleration *_ACCELERATION_BODY	Up to 1 Hz	Up to 1 Hz
Raw Acceleration *_ACCELERATION_RAW	Up to 5 Hz	Up to 5 Hz
Velocity *_VELOCITY	Up to 5 Hz	Up to 5 Hz
Fused Angular Velocity *_ANGULAR_RATE_FUSIONED	Up to 1 Hz	Up to 1 Hz
Raw Angular Velocity *_ANGULAR_RATE_RAW	Up to 1 Hz	Up to 1 Hz
Fused Altitude *_ALTITUDE_FUSED	Up to 5 Hz	Up to 5 Hz
Barometer Altitude *_ALTITUDE_BAROMETER	Up to 1 Hz	Up to 1 Hz
Home Point Altitude *_ALTITUDE_OF_HOMEPOINT	Up to 5 Hz	Up to 5 Hz
Fused Relative Ground Altitude *_HEIGHT_FUSION	Up to 1 Hz	Up to 1 Hz
Relative Ground Altitude *_HEIGHT_RELATIVE	Up to 5 Hz	Up to 5 Hz
Fused Position Coordinates *_POSITION_FUSED	Up to 1 Hz	Up to 1 Hz
GPS Date (YYYY-MM-DD) *_GPS_DATE	Up to 1 Hz	Up to 1 Hz
GPS Time (HH:MM:SS) *_GPS_TIME	Up to 1 Hz	Up to 1 Hz
GPS Position *_GPS_POSITION	Up to 1 Hz	Up to 50 Hz
GPS Velocity *_GPS_VELOCITY	Up to 5 Hz	Up to 50 Hz
GPS Details *_GPS_DETAILS	Up to 1 Hz	Up to 1 Hz
GPS Signal Strength *_GPS_SIGNAL_LEVEL	Up to 1 Hz	Up to 1 Hz
RTK Position *_RTK_POSITION	Up to 1 Hz	Up to 10 Hz
RTK Velocity *_RTK_VELOCITY	Up to 5 Hz	Up to 10 Hz
RTK Yaw *_RTK_YAW	Up to 1 Hz	Up to 10 Hz
RTK Position Info *_RTK_POSITION_INFO	Up to 1 Hz	Up to 10 Hz
RTK Yaw Info *_RTK_YAW_INFO	Up to 1 Hz	Up to 10 Hz
Timestamped RTK Info *_RTK_ALL_INFO	-	Up to 10 Hz
Compass Info *_COMPASS	Up to 1 Hz	Up to 1 Hz
Remote Control Joystick Info *_RC	Up to 1 Hz	Up to 1 Hz
Gimbal Angles *_GIMBAL_ANGLES	Up to 1 Hz	Up to 1 Hz
Gimbal Status *_GIMBAL_STATUS	Up to 1 Hz	Up to 1 Hz
Flight Status *_STATUS_FLIGHT	Up to 1 Hz	Up to 1 Hz
Flight Mode Status *_STATUS_DISPLAYMODE	Up to 1 Hz	Up to 1 Hz
Motor Start Error Code *_STATUS_MOTOR_START_ERROR	Up to 1 Hz	Up to 1 Hz
Battery Info *_BATTERY_INFO	Up to 1 Hz	Up to 1 Hz
Hardware Clock Sync *_HARD_SYNC	Up to 1 Hz	Up to 1 Hz
GPS Control Level *_GPS_CONTROL_LEVEL	Up to 1 Hz	Up to 1 Hz
Tagged RC Info *_RC_WITH_FLAG_DATA	Up to 1 Hz	Up to 1 Hz
ESC Data *_ESC_DATA	Up to 1 Hz	Up to 1 Hz
Gimbal Control Mode *_GIMBAL_CONTROL_MODE	Trigger-based	Up to 1 Hz
Cartesian Position *_POSITION_VO	Up to 1 Hz	Up to 1 Hz
Obstacle Avoidance Data *_AVOID_DATA	Up to 1 Hz	Up to 1 Hz
Home Point Set Status *_HOME_POINT_SET_STATUS	Up to 1 Hz	Up to 1 Hz
Home Point Info *_HOME_POINT_INFO	Up to 1 Hz	Up to 1 Hz
Battery Info (Index 1) *_BATTERY_SINGLE_INDEX1	Up to 1 Hz	Up to 1 Hz
Battery Info (Index 2) *_BATTERY_SINGLE_INDEX2	Up to 1 Hz	Up to 1 Hz
Timestamped Flight Attitude Info *_IMU_ATTI_NAVI_WITH_TIMESTAMP	Up to 1 Hz	Up to 1 Hz

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;
}