Maybe I haven’t explained the problem very clearly, so here is a more detailed explanation of the issue:
With the Pixhawk connected via USB to Mission Planner, in CONFIG/TUNING >> Extended Tuning, I have set CH6 Opt to “Rate Roll/Pitch kP”, I have set the min value to 0.08 and the max value to 0.20, and then clicked on “Write Params”.
With the CH6 knob on the transmitter turned fully CCW, I clicked on “Refresh Screen” and the value of P changed to 0.08 for both Roll and Pitch, which is correct.
With the CH6 knob on the transmitter turned fully CW, I clicked on “Refresh Screen” and the value of P changed to 0.20 for both Roll and Pitch, which is also correct.
So far, so good …
However, when I turn the CH6 knob on the transmitter to the mid-point and click on “Refresh Screen”, the value of P is displayed as 0.20 for both Roll and Pitch. This is not correct as the value displayed should be around 0.14 (the mid-point between 0.08 and 0.20).
If I use the “Radio Calibration” part of MP to check the value of channel 6 as reported by the Pixhawk, it shows as 1500 uS, which is correct (midway between 1000 uS and 2000 uS).
If I rotate the CH6 knob slightly CCW, so that the “Radio Calibration” reports the channel 6 value as 1450 uS, then when I click on “Refresh Screen”, the value of P is displayed as 0.08 for both Roll and Pitch.
It looks like the code behind the CH6 Opt “Rate Roll/Pitch kP” is interpreting the channel 6 signal as a toggle switch (binary values of 0.20 and 0.08) instead of a variable potentiometer with a wide range of possible values?
So, if I tried to use the channel 6 potentiometer to adjust the value of P for pitch and roll while flying the quadcopter, then all I would be able to do is toggle the value of P from 0.20 to 0.08 to 0.20. But, I need to be able to select any value between 0.08 and 0.20.
Either I am doing something really dumb, or this is a bug in the code behind “Rate Roll/Pitch kP” …