"Once again on this topic.
I don't really understand why can't APM have Z axis autotune. Well, maybe it have no resource for kalmann filter, but some simple features and some minor improvements could be done."

"Solved.
Solution is here. In lower part. Glad to say, that current PX4+IO controller files and performing very well."

"On top of all I have ground on 1st pin of MULTI port (should be VDD_5V).
That's a bad thing that APM got dropped out of support. This board solved everything in couple of hours instead of having headache for days."

"AFAIG we have our VQuad mixers in this file.
In particular this place:
}else if( _flags.frame_orientation == AP_MOTORS_V_FRAME ) {
// V frame set-up
add_motor(AP_MOTORS_MOT_1, 45, 0.7981f, 1);
add_motor(AP_MOTORS_MOT_2, -135, 1.0000f, 3);…"

"According to this guy's logic right here, all I have to do is to change output channel in code, but it's too weary to compile everything from scratch each time."

"Important thing. Channel failed on PX4IO module."

"Good point, same situation here.
I was testing brand new copter frame when it slightly (intended) hit the wall. Power surge (unfortunately ESC had no OPTO isolation) seems have damaged third channel (coincidence?). Channel 3 is "no go" anymore.
I'm…"

"Thanks Randy,
I've seen this page, but I'll take closer look at it once more."

"Do anyone know if I can use solid state relays on my PX4IO board and how should I setup em (map to specific RC channel) if answer is positive.
Is it possible to turn em on say on "arm" action?"

"I guess there is limitation on PX4FLOW focus. Did you set up sensor focus as it is said in Wiki? I got mine adjusted to 3m distance, and it was NOT set up correctly out of the box (as it is also said in wiki).
I am currently using:
PX4 + IO(stack) +…"

"No, you should adjust PIDs separately on these boards. But you don't have to do it byhand, there is splendid "autotune" mode."