X9D Telemetry page - RSSI Source [---]?

Hi all-

I’m trying to set up telemetry on our quad and I’ve run into a problem that I cannot find any references to, so I thought I’d shoot it past the collected wisdom of the forum.

The hardware in question: Pixhawk 4, R-XSR receiver, Taranis X9D Plus 2019 (OpenTX, latest).

In order to get the receiver bound to the TX, had to I flash both with the latest firmware. Now Channels 1-4 are responding normally (ACCST D16 mode).

So far I have wired the S.Port of the R-XSR to the TX of the TELEM1 port on the Pixhawk. I have tried setting the parameter SERIAL1_PROTOCOL to both 4 (FrSky Sbus) and 10 (FrSky SPort Passthrough), and neither is working so far.

Here’s what I see:

When I long press on the [Source — ] I get only beeps. I have also tried discovering sensors, which fails also.

Any suggestions would be much appreciated!

What flight controller is that?
Most will need a TLL/RS232 adapter circuit. See

Thanks for the suggestion, Shawn, The FC is a Pixhawk 4, which (from what I have read) contains an FMUv5 processor which automatically detects inputs to UARTs.

However, I did notice that I had only flashed the RF firmware on the Taranis, and not OpenTX. (That was to get the ACCST D16 mode on both the R-XSR and the Taranis, which now seems to be working.) So I just flashed the latest OpenTX to the Taranis, and now instead of [—] under telemetry, I see (default). Which seems like an improvement, but unfortunately I’m still not discovering any sensors or seeing any RSSI info.

Should I try enabling ACCESS mode? Offhand I can’t recall exactly why I thought I needed to switch to ACCST mode, but I think it had something to do with not seeing D16 mode under the radio setup for this model.

Patrick

Yeah I saw it was a Pixhawk 4 after I wrote that question :slight_smile:
You might need to experiment with these options, available for all serial ports but serial 4 linked here as an example. It’s a bitmask value, so combine the bits you need set and convert to a decimal value and plug that in.
SERIAL4_OPTIONS https://ardupilot.org/copter/docs/parameters.html#serial4-options-serial4-options

For a CUAV V5 Nano I had to use a (real/physical) pull down resistor (2k ohms) between TX and 0v and these settings:

  • SERIAL4_PROTOCOL,10
  • SERIAL4_OPTIONS,7

I didn’t have the pull up and pull down options available on this FC. Some of the OPTIONS settings are only available depending on the capabilities of your FC.

Shawn-

Yikes…I wasn’t expecting any uart hardware hacking to be necessary, but…

I’m a little confused…you said you used a 2K pulldown between TX and gnd. However bit 7 is a pullup. But not having pullup/down options on your FC seems like you wired it for bit 6 (TX_pulldown) being set without actually setting the parameter that way, and it worked! Before I go pulling on the TX port one way or another, could you please clarify?

So if I do go with a pullup on the TX of, say TELEM1 (SERIAL1) I would set SERIAL1_OPTIONS to 64…correct?

Thanks very much-

Patrick

Ahhh, I just checked and the Pixhawk 4 (PX4) does NOT have SERIALN_OPTIONS. So I guess I’ll just try a pulldown and see if that helps. My FC has the same processor as the Nano (although the IO processor might be different- I couldn’t find that data for the Nano).

Patrick

SERIALx_OPTION,7 would be:
bit0 InvertRX (value 1)
bit1 InvertTX (value 2)
bit2 HalfDuplex (value 4)
= 1+2+4
and the bit0 setting might be not needed since we only use the TX line anyway. So in theory SERIALx_OPTION,6 could work just as well for me. I’ll test this to be sure.

The pull-down resistor I’m using is in the wiring between the FC and the receiver, so not much hacking involved at all.

If you dont have any of the SERAILx_OPTIONS then you’ll definitely need one of the external RS232/TTL converters.

Turns out I was wrong about the Pixhawk 4 firmware not having SERIALN_OPTION…so I’m about to try the options you mentioned with the TX pulldown.

Patrick