Difference in IOMCU and "regular" out ports regarding handling input signals

Would someone please confirm or correct my understanding on this topic?

I understand that IOMCU ports do not have the ability to handle input signals. Is this true?

If so - is this a hardware or a firmware restriction?

I understand that things like camera hot-shoe signals have to be connected to non-IOMCU (AUX) ports - perhaps for this reason. Similarly, passthrough for BLHeliSuite32 requires motor connections to AUX ports - perhaps because it requires the AUX port to receive input signals.

I’m trying to wade through the history of threads regarding bi-directional dshot. As near as I can tell bi-directional dshot requires non-IOMCU (AUX) ports - presumably because “bi-directional” means signaling is also going back to the flight controller.

Many Thanks!

You can use any servo port as GPIO, the Dshot issue is to do with the timers connected to specific groups of pins not it’s input capability. Thats why you usually have to enable Dshot on a groups of pins as they share a timer.

Thank you GeoMuir -

Yes - I noticed the firmware change a few revisions ago that now allow IOMCU ports to function as GPIO relays. I’ve used this function to trigger a camera shutter on a IOMCU (main) port - works great.

As I understand it however, the GPIO capability on IOMCU ports is still output only. So for example, I can’t use a IOMCU port for camera hot-shoe input. Is this still correct?

Thank you also about your comment regarding dshot. I’m finding that a lot of the confusion in the discussion threads is because “regular” dshot and “bi-directional” dshot have different requirements - and this distinction isn’t always made clear in the discussions.

As best as I can tell, “regular” dshot works on any port - IOMCU and non-IOMCU.

What I’m not clear about yet is the requirement for bi-directional dshot. I think this requires a non-IOMCU port - and there are some flight controller limitations and/or restrictions.

If you can comment on that, or perhaps point me to a link with current information, I’d appreciate it very much.

Thank you.

Im sure I use button input buttons and relays on regular outputs or aux on my pixhawk1. but I dont know if the hotshoe has other requirents. if you have Dhot enabled then you have to watch what groups of ports are assigned to dhot as you wont be able to use them for anything else. I think its aux 1-4 and aux 5-6. so if you use any of them for dshot the rest in that group will be unavailable for anything else. so even if your only using one dshot motor on aux 1, then aux 2 3 4 wont do anything other than dshot.