UM982 RTK Configuration

FlyCore-FC integrates a UM982 RTK module. The module communicates with PX4 through the flight controller's internal GPS1 link, so there is no need to connect an additional serial port to the module. For the pin assignments of the antenna and RTK-related interfaces, see Appendix: FlyCore-FC Interfaces and Pin Definitions.

Basic Communication Parameters

GPS_1_CONFIG = GPS1
SER_GPS1_BAUD = 230400
GPS_1_PROTOCOL = NMEA

Dual-Antenna Heading

Prerequisites

• Confirm the Primary and Secondary antenna interfaces.
• Ensure that the primary and secondary antennas are unobstructed. A straight-line distance of at least 30 cm between the two antennas is recommended.
• If only single-antenna positioning is used without heading determination, connect the antenna to the primary antenna interface.

Configuration Steps

1. Connect the primary and secondary antennas, and verify their physical positions.

2. Set the following in the QGC parameter list:

   SER_GPS1_BAUD = 230400
   GPS_1_PROTOCOL = NMEA
   

3. Enable Dual antenna heading in EKF2_GPS_CTRL.

4. Set GPS_YAW_OFFSET according to the position of the primary antenna relative to the nose. The angle increases clockwise:

   • Primary antenna directly in front of the nose and secondary antenna at the tail: GPS_YAW_OFFSET = 0;
   • Primary antenna on the right side of the airframe and secondary antenna on the left side: GPS_YAW_OFFSET = 90.

5. Save the parameters and restart the flight controller.

Readback and Status Verification

• After the restart, the parameter values match the target configuration;
• QGC recognizes the GPS normally, and the satellite count meets the mission requirements;
• The heading is stable and changes in the correct direction as the airframe rotates;
• PX4 reports no GPS or EKF warnings.

Reversing the primary and secondary antennas, using a baseline that is too short, or setting GPS_YAW_OFFSET inconsistently with the actual installation will affect heading calculation.

RTCM Differential Data Injection

• External injection: After receiving RTCM data, the video and data transmission module forwards it to the positioning module through a serial link.
• Onboard system injection: FlyCore-U receives and forwards RTCM data to the positioning module.

After correction data is received, the GPS status in QGC changes to RTK Float or RTK Fixed.

Post-Injection Checks

1. Confirm that QGC recognizes the GPS and that the satellite count meets the current mission requirements.
2. Confirm that RTCM data continues to arrive.
3. Check whether the Fix_type status equals 6, and confirm that the heading is stable.

For the selection of the positioning source and fusion parameters, see FlyCore-FC EKF2 and VIO Configuration.