Problem rfd900x (pixhawk 3 pro)

Hardware Radios
1

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!

2

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

3

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…

4

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?

5

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