I’m running Cleanflight 1.10 on a CC3D flight controller. In order to update to the latest Cleanflight release I would have to reflash the CC3D as releases after 1.10 aren’t compatible with the standard CC3D bootloader. This means I don’t have airmode, so decided to implement idle-up instead.
Idle-up is simply a switch that raises the idle point of the throttle sufficiently high for the PID controller to become fully active, including the integral term that is disabled at low throttle even if pid_at_min_throttle is set. This allows you to set the throttle to idle during aerobatic manouevres without the reduction in stability that results if the PID loop is not fully active.
Since I switch arm using switch C (the left shoulder switch on the Futaba T6K transmitter), which is a three-position switch, I decided to allocate the switch as follows:
- Up is disarmed
- Centre is armed, with normal (low) idle
- Down is armed, with idle up.
To achieve this, I simply created a new throttle curve (THR CRV) for SWC (DN)and set value P-1 (corresponding to the throttle being fully off) to 10% instead of 0%. This gives a throttle value (as seen on the Cleanflight receiver screen) of just over 1100, which is sufficient to ensure a fully functional PID loop. Actually 9% was the minimum required to activate the I-term in my setup,but I thought I would give it little margin. It is easy to tell what the minimum value required is because if you arm the quad with the switch in the idle-up position(props off of course), and then gradually increase the P-1 value that sets the idle level, then you will hear the motors start winding up as soon as the I-term is active. That level, or just above it, is where you should leave your idle.
As a bonus, I also set the throttle curve when Switch C is in the Up position to 0% for all stick settings. This ensures that the quad will disarm irrespective of the throttle setting when the switch is in this position. I know that Cleanflight has a setting for this, but I found that occasionally there would be a glitch on the channel during normal flight and the quad would disarm in midair, so I turned it off. Now I have the same functionality, but because it depends on two channel settings (throttle and arm switch) being transmitted over the air, hopefully glitches won’t cause it to disarm!
Postscript
Of course you have to be careful when testing the difference between idle-up and normal idle not to accidentally move the switch two positions, thereby disarming the quad in mid-air. At least I know the disarm is working properly as a motor kill switch!!!