IMU selection

m4v3r

Hi,
I am absolutely confused over the IMU's onboard the VOXL Flight:
From the documentation, there should be 2 on the VOXL-side and three on the Flight Core -side.

As I understand one would use the "IMU_" parameters to set which one to use but there aren't any ID's published that one would use.

In theory, shouldn't I be able to "select" the ICM-20948 and be set for flight w/o GPS, given that it includes a magnetometer?

So how can I use the onboard IMUs on the VOXL Flight is my question I guess?
Please tell me I do not have to learn how to build firmware for that, do I?

thanks in advance for any insight into this.
cheers

modaltb

Hi @m4v3r ,

Although you are not wrong and we've wanted to do similar, the PX4 FW has access to ICM-42688, ICM-20602 and BMI-088, and the "VOXL" side (where Linux is running) has access to the 20948 (and additional 42688)...

Some info here: https://docs.modalai.com/voxl-flight-datasheet-imus/#summary

The VOXL side IMUs are intended for CV use, where the PX4 side IMUs for PX4.

Folks wanting to use a mag traditionally have used an external device to get good performance.

For reference, here's where the PX4 IMUs are started: https://github.com/PX4/PX4-Autopilot/blob/master/boards/modalai/fc-v1/init/rc.board_sensors#L13

On the VOXL side, we use a publish IMU data via this: https://gitlab.com/voxl-public/modal-pipe-architecture/voxl-imu-server

But you'll see we aren't using mag data...
https://gitlab.com/voxl-public/modal-pipe-architecture/libmodal_pipe/-/blob/master/library/include/modal_pipe_interfaces.h#L347

Feel free to keep questions coming!

m4v3r

@modaltb thanks, I only have one follow-up and it might be a dumb question but was is meant by "CV use"?
I personally am the technician and pilot for our VOXLs coming from a Betaflight background, so the whole companion-computer deal is quite new to me...^^

The reason behind wanting to use the internal mag is that I cannot for the life of me get a second GPS to work but I'll describe that whole problem in a new thread.

Thanks again for the references, I'll hand that to our code-guys on Monday.

modaltb

"CV" for computer vision (we use IMU data with camera frames on the companion computer to do some math to provide localization data).

OK I'll watch out for the other thread, the GPS/mag normally work OK so hopefully we can resolve that!

m4v3r

Computer Vision, of course. =D
Since working with the VOXL I already learned RTK, VIO, EKF and so on... but this one escaped me, so thanks haha.^^