Help! XM+ binds, but no inputs

[bhester91]

I was in the process of upgrading the VTX and Rx on my Tinyhawk Freestyle and after finishing up I bound my QX7 to the XM+ (got the green light), but when I go into betaflight I don't get any inputs from the receiver.

I made sure serial rx was set to UART1 and it is configured SBUS. I also tried UART2 and still nothing.

Any help would be greatly appreciated!

 

[HighTechPauper]

Check this video at 8:05, see if that helps. My guess is that the RX1 pad is and un-inverted UART input, and the SBUS pad goes through an inverter first before it hits the UART. I did not watch the whole thing to see which port he configured as Serial RX, but I would guess it would be easy enough to test and find, but my guess here is port 1.

 

[bhester91]

So I watched his video and I tried soldering to each pad with no luck on either. I also read that inverting could work so I did serialrx_inverted=on in CLI with no luck.

 

[bhester91]

When I am setting up the serial Rx on UART1 should those setting stay after the reboot? This is what I set it to.

Screenshot (1).png

• bhester91
• May 29, 2020

and this is what it goes back to after the save and reboot.

Screenshot (2).png

• bhester91
• May 29, 2020

 

[bhester91]

Also this is how the XM+ is wired to the board.

20200529_164001.jpg

• bhester91
• May 29, 2020
• 1

 

[bhester91]

Disregard! After posting my pictures I realized I only needed to click Serial Rx and not configuration. I feel dumb now haha

 

[tevek]

Disregard! After posting my pictures I realized I only needed to click Serial Rx and not configuration. I feel dumb now haha

A couple of weeks ago I hit a tree and tore off the wiring to the Rx. Resoldered it and for whatever reason it would bind but wouldn't arm. I was in a crap mood and did essentially what you have done and despite looking at the ports tab and knowing it wasn't right, I kept mucking around with it. In the end, I simply pasted the original setup/file that I dumped from the CLI, the correct settings popped up and was good to go. Lesson to self: always back up the standard settings before I even both taking the thing out for its maiden flight.

 

[HighTechPauper]

Ok, a couple things...

You shouldn't be setting MSP on UART1, just Serial RX, a port can only have 1 function, not 2, that is likely what is keeping it from saving.

That exposed length on the wires, on the RX especially, and probably the black on the FC too, are way too long, in the slightest crash they can bend and touch and short out.

I wish I knew a little more about the FC/ESC in those so I could be a little more certain, but there is almost no clear documentation out there on them.

 

[bhester91]

Yep that was the issue! I don't know why I kept checking that slider, but when I realized what I did I felt really dumb for wasting so much time trying to figure it out. As for the wires, I ended up redoing pretty much all of it to clean it up and added heat shrink around the ends. Wish I would have taken those screenshots sooner!