Issue with MAVLink RC Link on INAV 8 using TBS Crossfire

[tedre191]

I’ve been trying to set up the new MAVLink RC feature in INAV 8.1 with two aircraft, but haven’t been able to get it working.

All documentation I’ve found seems to reference ELRS Crossfire, but I’m using TBS Crossfire modules. Could this be the reason it doesn’t work? Does it even matter?

Here’s what I’ve tried so far:
• Selected the correct UART in INAV and set it to MAVLink.
• Configured the receiver protocol as Serial (MAVLink).
• Set the Crossfire receiver output channels to MAVL RX/TX.
• Enabled RC by MAVLink on the TBS TX side.
• Tried with and without the CLI command highlighted in the documentation too (set mavlink_radio_type = ELRS)

Despite this, I don’t see any RC data coming through INAV. The same setup works fine on both aircraft with ArduPilot; the same connections work with CRSF as the serial protocol on both aircraft as well on INAV.

Question:
Is MAVLink RC supported with TBS Crossfire in INAV 8, or is it only supported with ELRS Crossfire?
If it should work with TBS, what configuration step might I be missing? I'm not running the latest firmware on the TBS side, but close to it (6.36). We'll try to update that too tonight, but the release notes don't mention anything about MAVLINK or INAV.

Thanks in advance for your help!

[ja51d]

the set mavlink_radio_type = ELRS thing isn't your problem - that setting only changes how RSSI/LQ get shown on the OSD, it doesn't turn RC on or off.

the actual issue: iNav's "RC over MAVLink" only listens for RC_CHANNELS_OVERRIDE messages (you can see it in src/main/rx/mavlink.c). so for sticks to show up, something on the radio link has to actually inject your stick positions into the mavlink stream as RC_CHANNELS_OVERRIDE. that's what ELRS's mavlink mode does. TBS Crossfire's mavlink mode is really just a telemetry bridge between the FC and your GCS - it tunnels mavlink for the ground station, but it doesn't send your gimbals down to the FC as RC_CHANNELS_OVERRIDE. so the FC sees telemetry going out but no RC coming in, which matches exactly what you're seeing.

that's also why plain CRSF works - on crossfire the sticks come through the normal crsf channels.

so short version: on TBS Crossfire, just use CRSF for the control link (it works), and you can still run mavlink telemetry separately if you want a GCS. mavlink-RC is really the ELRS path. it's not a config step you're missing on the iNav side.