SPort connection to RXSR-FC board

[Allan Bennett]

Having successfully (I think) upgraded my Taranis 9D+ 2019 transmitter to v2.1.0 firmware, I now need to do my receivers, and want to start with an FXSR-FC board in my 250 quad.

The RXSR receiver is factory-mounted onto the back of an Omnibus F4 flight controller board, and its SBus outputs are inaccessible to me. But the FC board itself has an SBus pad, so I presume that all I need to do is connect a standard servo socket signal wire to the SBus pad, and the + and - wires to the 5V DC and GND pads on the board, to give myself an easily accessible SPort connection.

I'd rather not just suck-it-and-see, in case I damage something, so can anyone confirm that my thinking is right please? I'll be using my laptop and a FrSky STK SPort tool, rather than the transmitter, to do the update.

[Bob Cotsford]

Google helps sometimes

[Allan Bennett]

Thanks for that quick reply Bob. Google is indeed helpful, if you know the right search terms! Anyway I've read your link, configured my quad's UART2 to SPort, and installed FrSky's Update Sport program onto my laptop, but it won't run due to .dll files not found, and other errors. I'll have another go tomorrow. Thanks.

[Allan Bennett]

This is not working for me

I've got the FrSky update tool working, but it's unable to find the device.

I've followed the instructions in Bob's link, but my first problem is I'm confused by the the message in Betaflight's CLI screen which says "Forwarding, power cycle to exit" after it reports that Port 2 is opened. Power cycle what, and how? The only way to power cycle the receiver is to disconnect it from the USB port, since that's where it's getting power from at the moment. I thought that inputting "Exit" at the CLI line would save the changes.

Anyway, after I've done that, then reconnected the receiver to the USB. I start the FrSky update tool as Administrator, select the firmware update file that I've previously saved, and the update tool correctly recognises the COM port but gets stuck on "finding device".

At the moment soldering three wires to the board to give it an SPort socket seems to be the simplest way to do the update, so is anyone able to confirm, or otherwise, that the method I describe in my opening post is correct please?

[Allan Bennett]

Github.com has clarified my question about the "Forwarding, power cycle to exit" message, but I've tried serialpassthrough again today, trying three spare UARTs in turn, and the FrSky update tool is unable to find my device whichever one I use, even though it's automatically selected the correct COM port. My receiver does not power on when I connect to USB (which Github says is correct), so I then connect external power to it when connecting to the update tool.

So any ideas please, about serialpassthrough or the SPort connection on the top side of the board?

Edited By Allan Bennett on 23/05/2020 15:56:42

[Allan Bennett]

Problem solved

Actually I've circumvented the problem! I plucked up the courage to extract the RXSR receiver from it's little mounting box on the FC board and soldered three wires direct to its ~+- S.Port pads, then used my FrSky STK tool to do the firmware update with direct connection to the RXSR S.Port.