Build Plan

The following is my build plan.
I’m trying to put all this in a 3" Whoop frame.

There are a lot of pieces to get working…
My plan is:
1)To get DJI airunit , ESC, basic FC working with Betaflight.
Where the DJI unit was running SBUS to provide RC into the FC.

2)Then Add the Crossfire Tx/RX swithc to TX16S/OpenTx Tx.

3)Then get the same set of parts working on PX4.

4)Then Get Mavlink working over the Crossfire

5)Work on basic PX4 tuning.

6)Then add GPS/ Magnetometer.
Work on Alt/Poshold tune.

7)Then Add Lidar/Optical Flow.
Work on Optical flow/Alt Pos hold tuning.

Several questions…
1)Anything fundamentally wrong with my plan?

2)Should I be using some other flight controller rather than the KAKUTE F7?

3)Has anybody gotten MSP telemetry working from PX4 to DJI airunit?

4)If I have a decent manual PID loop tune working in Betaflight can I transfer any of that information to PX4, or am I basically starting from scratch?

5)The KAKUTE F7 HDV does not have an isolated IMU. (MPU6000)
There is a version of KaKUTE V1.5 that does have an isolated IMU?
Should I be starting with that?

Thanks for any help.

What do you mean by DJI air unit?

The DJI FPV Airunit digital video transmitter module.
It transmits low latency high quality 720p video,
It also has a receiver built in that outputs sbus…

I’m just about done with step 2 in the plan.
I’ve not yet flown it with beta flight, but I did go ahead and get the crossfire rx and opentx working with betaflight on the bench. So it should have its betaflight first flight some time today…

I’m currently working on a quad with px4 running on a holybro kakute f7 v1.5. To answer your questions 2, 4 and 5:

  1. The kakute F7 works perfectly fine with px4. Due to its constrained flash, you have to disable some modules, drivers and system commands in order to get the ekf2 global state estimator module working (which gives the best performance according to what I’ve seen).

  2. I would start from scratch. For a 5 inch quad with 6 inch props and 1750kV motors on 2S, it works pretty decently out of the box. I would not copy the betaflight pids since they have a different contoller scheme and their gains are in other units (PX4 gains are usually between 0 and 1.5, betaflight is usually above 30).

  3. The only difference would be that you have to use rubber rings to softmount the entire flightcontroller. The 1.5 does not have to be soft mounted, saving 5 seconds while mounting it. The performance should be similar.

I myself don’t use the sbus connection and use rc over mavlink with crossfire. That’s just personal preference. With sbus (or crossfire serial connection (which is also supported by px4), you can get telemetry information like altitude, flight mode, etc on your radio as well.

I would also add the gps/magnetometer and lidar/optical flow before tuning the quad. It doesn’t have to be functional yet, but it changes the weight and weight distritbution of the quad, which affects your tune.