Pixhawk 4 and DShot ESCs

Just a quick caveat to those who are considering using the Pixhawk 4 FC for their builds.

There’s a massive hardware limitation when using the DShot protocol instead of OneShot or MultiShot. You have to disable the IO chip which normally handles the MAIN channels and route them through the master FMU, halving the number of channels available from 16 to 8. On top of that, due to hardware interrupt conflicts you can only use DShot on 4 of those FMU channels, thereby halving available motor channels once again. This means you literally cannot have a hexa- or octarotor and use DShot. You may as well use a Pixhawk 4 Mini which doesn’t have an IO chip on it, and is cheaper, smaller, and lighter.

Why use DShot? Well apparently it’s more robust than the earlier protocols, and you get ESC telemetry.

Ultimately UAVCAN devices will be the way forward, but as far as I can tell they’re much more expensive, there’s less choice, and they only seem to go up to 20A

Some poking around has found UC4H which, amongst other things, implements a UAVCAN to DShot interface. Definitely something I will be looking into.