[Bug] MAVLink IMU dropouts in SITL #26230
Description
Describe the bug
I am integrating PX4 with a custom built EKF via MAVSDK that depends on consistent IMU timing. In SITL testing, I am receiving a high rate of IMU message dropouts via the SCALED_IMU message when requesting via MAVSDK.
To Reproduce
If I add a print statement to SCALED_IMU.hpp to print the delta time of msg.time_boot_ms with the previous iteration, I would expect a consistent value of approximately 0.0040 s.
float delta_t_s = (float) (msg.time_boot_ms - previous_time_ms) / 1000.0f;
PX4_INFO("Scaled IMU dt: %.4f s",(double) delta_t_s);
previous_time_ms = msg.time_boot_ms;In reality, I also observe a significant number of 0.0080 s and 0.0000 s which is an indication that there are dropped and duplicate samples.
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0080 s
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0080 s
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0000 s
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0080 s
INFO [mavlink] Scaled IMU dt: 0.0000 s
INFO [mavlink] Scaled IMU dt: 0.0080 s
INFO [mavlink] Scaled IMU dt: 0.0040 s
INFO [mavlink] Scaled IMU dt: 0.0080 s
Expected behavior
If I add a print statement to VehicleIMU.cpp to print the delta time of imu.timestamp, I get a consistent rate:
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
INFO [vehicle_imu] vehicle_imu dt: 0.0040 s
This implies the simulator is producing consistent IMU messages, but that the timing is corrupted when pulling the data from the uorb stream.
Screenshot / Media
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Flight Log
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Software Version
I have validated this behavior occurs with PX4 v1.14.4 and v1.16.0. It is simulator agnostic as both Gazebo Classic and the new Gazebo. I am running on a Ubuntu 22.04 virtual machine.
Flight controller
PX4 SITL
Vehicle type
Multicopter
How are the different components wired up (including port information)
No response
Additional context
No response