Hi all.
We were using PWM MAIN (I/O PWM) outputs for controlling the ESCs of our multicopters for a long time. Now we noticed some discrepancies within PX4 documentation regarding connecting ESCs.
According to Actuator configuration documentation, we should use PWM AUX (FMU board output) for controlling motors as they are supposed to have lower latency.
We are currently using Pixhawk 6X. According to Pixhawk 6X documentation, we should connect ESCs to I/O PWM outputs as we were doing.
What is the best way to connect ESCs with lowest latency?
Thanks for answers.
Michal
FMU Outputs have lower latency.
It’s not really a discrepeancy - the QGC config example uses the FMU ouputs by default configuration - because they have lower latency,
Thank you for answer @jcdonelson.
It is a bit confusing, because you can read opposite recommendation in current PX4 documentation and historically in era before dynamic control allocation (older firmwares 1.12 and earlier) ESCs were connected to MAIN outputs (I/O), see older airframe reference
Yes, and in most cases people used the default mixers and didn’t worry much about latency.
The exception was racer setups, which explicitly recommended disabling the IO in Racer Setup | PX4 User Guide (v1.12) - the MAIN pins then get mapped magically to the FMU.
I’m not sure how necessary it is to chase the lowest latency, though anecdotally Dshot esc are better in this respect to the other supported protocols.
Note, I can’t address your issue in docs. We update the current docs when we get to them - and the advice to use MAIN (usually on I/O) makes sense for the older releases.
Thank you for clarification. I assume, that the difference in latencies is negligible.
