Problem rfd900x (pixhawk 3 pro)

Hey, I’ve connected my rfd900x to pixhawk 3 pro at telem 1. The connection works just fine when I power my pixhawk from USB (connected to my computer). But, when I power the quad with a lipo, the rfd900x shows a flickering orange led, momentarily, and then no light or any indication that its’ powered on. All my other sensors/accessories (gps, rx, etc) are functioning normally.

So it seems as if the USB provides sufficient power to telem1 to run the rfd900x but not the lipo / power module (Mauch PM). Any suggestions or ideas?

Unless someone has a solution, I’ll try to power the rfd900x with a separate 5v bec and connect only TX/RX and CTS/RTS between radio and pixhawk. That may work just fine but its’ an added complication that I’d hoped to avoid… Thanks!

You really should power it separately. Make sure you connect gnd to the Pixhawk too.

Thanks for response and I have powered it separately (5v bec to pins 2&4) and its’ all functioning normally. I disconnected 5v and ground in my cable between radio & pixhawk but I’ll go back and reconnect that ground - thanks for that tip.

I still think its weird that the usb port powers the radio sufficiently but not lipo…

So I’ve powered my rfd900x via 5v bec and I’ve powered my pixhawk via a different 5v bec (mauch power module). When I connect ground between rfd900x and pixhawk, am I not creating a ground loop? if so, is that not a problem?

You need the common ground to ensure the logic levels have the same reference.