i have ask Eric Stockenstrom - zs6buj this is the way the mavlink to passthrough works
Yeah, we installed a PR from hasil123 back in 2020-01-18 v2.51
if(fr_rssi < 1){ // Patch from hasi123 fr_rssi = 69; }
The purpose was to ensure connectivity to the Taranis et al, even when there was a problem with rssi. Before that we had
//#define RSSI_Override // Dummy RSSI - fixed at 70%
Further, I continue to send rssi even if we lose Mavlink telemetry. We did this because on some long-range radios telemetry would time out, rssi to Taranis would stop, and Taranis screen stops updating.
So it’s a bit of a mish mash and could benefit from a logic clean up.
Since then we increased the telemetry time-out to 10 seconds, so it’s probably ok to stop forwarding (the most recent) rssi on the downlink when the uplink is broken.
Also, maybe 69 is a bit odd, so I could make it say 70% when rssi == 0, but only if
(#defined RSSI_Override) is true.
so its to fix openTX issue not updating