Mavlink over ELRS: No telemetry in EdgeTx until QGroundControl connected via WiFi

[maciek252]

Hello,

I use mavlink over ELRS (it is very good) but I've noticed that the telemetry in EdgeTx starts being displayed and updated only after I connect a QGroundControl instance via WiFi from the ELRS backpack. Sometimes I would want to have this EdgeTx telemetry display running withouth the QGroundControl, just to know the stuff like the battery voltage and num of sats.

Is this possible? What can be the reason for this behaviour? Setting correct Mavlink rates by QGC? Is there any setting in EdgeTx which could initialize the telemetry correctly?

I tested this on the newest ELRS v3 and v4 versions. EdgeTx was 2.11.4. I do not understand very well the inner details of the conversion Mavlink->CSRF.

BTW I've posted the same question to the ExpressLRS discussion forum as well, as I'm not sure which one is more relevant (maybe both?) The same problem occurs on a Taranis X-Lite running OpenTx.

[ja51d]

this is normal mavlink behaviour, nothing wrong with your elrs setup. the flight controller doesn't just blast telemetry on its own - it waits for the other end to request the data streams. when you open QGC over the backpack wifi, QGC sends those stream requests, the FC starts emitting SYS_STATUS, GPS_RAW etc, and that's what edgetx finally has to read. close QGC and nothing's requesting anymore so the FC goes quiet again. that's why it only works while QGC is connected.

if you're on ardupilot, the fix is to set the stream rate params for the serial port your elrs rx is wired to, so the FC streams without waiting for a GCS. for the port = SERIALn, set:

• SRn_EXT_STAT -> battery voltage + gps sats (the stuff you want)
• SRn_EXTRA1 -> attitude
• SRn_POSITION -> position

set them to something like 2-4 hz and save. after that edgetx should show telemetry straight after boot, no QGC needed.

(if you're on px4 it's the same idea but you configure it on the MAV instance for that port instead of SR params.)