What is PWM_ACHDIS?

ealdaz · February 15, 2017, 10:50am

Dear all,

I’ve seen in many of the configuration files for vtol airframes that there is a parameter PWM_ACHDIS such as:

set PWM_ACHDIS 5

The number it is set to seems to be related to what channel the throttle is mapped to in the AUX Channel.

Any idea’s of what it’s used for?
Thanks

dagar · February 15, 2017, 7:46pm

It’s used for setting the disarmed value for the fixedwing motor on the AUX channel.

github.com

PX4/Firmware/blob/494d2c9ecf4a5eb984974455cdf3848ed47cfdd8/ROMFS/px4fmu_common/init.d/rc.interface#L228


		if [ $PWM_ACHDIS == none ]
		then
			set PWM_ACHDIS ${PWM_AUX_OUT}
		fi


		#
		# Set disarmed, min and max PWM_AUX values
		#
		if [ $PWM_AUX_DISARMED != none -a $PWM_ACHDIS != none ]
		then
			pwm disarmed -e -c ${PWM_ACHDIS} -p ${PWM_AUX_DISARMED} -d ${OUTPUT_AUX_DEV}
		fi


		if [ $FAILSAFE_AUX != none ]
		then
			pwm failsafe -e -d ${OUTPUT_AUX_DEV} ${FAILSAFE}
		fi


	fi
fi

ealdaz · February 15, 2017, 9:08pm

I see, so this a way to specify a disarmed value only for the channel/s specified as opposed to all of them as would be the case when using PWM_AUX_DISARMED on it’s own.

Why is this necessary? Is this related to mixing servos and motors in PWM_AUX ?

Why is there no PWM_ACHDIS for MAIN? Does this mean that only motors are meant to be used in PWM_MAIN?

I haven’t used servos yet, but now wondering how you’d specify different Disarmed values for each of them…

Can you provide a bit of context for this please?
Thanks