QGC multi-vehicle: connect/disconnect flicker >3 drones (COM_DLL_EXCEPT/COM_DL_LOSS_T questions)

QGroundControl Development
1

When I connect more than 3 PX4 vehicles to QGroundControl, some start rapidly flipping between Ready and Not Ready with repeated “connection lost/regained” messages. It’s not always the same vehicles, but a few from the group. Limiting failsafe behavior by setting COM_DLL_EXCEPT reduced the visible flicker, but I’m not sure that’s actually safe or addressing the root cause.

I was considering increasing COM_DL_LOSS_T, but I’m unsure whether that just delays the inevitable failsafe or if it helps during the initial connect phase when multiple vehicles come online together.

Setup (high level):

  • PX4 (multiple airframes), unique MAV_SYS_IDs

  • Wi-Fi UDP to QGC, default autoconnect (14550)

  • 3 simultaneous vehicles triggers the issue; ≤3 is stable

Questions:

  1. Is there a recommended upper limit for simultaneous QGC vehicles on one GCS/port?

  2. Would raising COM_DL_LOSS_T meaningfully help during connect bursts, or just mask real link drops?

  3. Any best practices for multi-vehicle UDP (e.g., unicast to unique ports per vehicle and adding QGC Comm Links vs. all on 14550 broadcast)?

  4. Guidance on stream rate tuning to keep QGC responsive (PX4 MAV_x_RATE, SRx rates) for multi-vehicle?

  5. Any known QGC settings that reduce UI/heartbeat thrash with many vehicles?

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here is it switching from ready to not ready due to connection error

3

I’d have a look using Wireshark to see what is going on exactly. And if you’re doing this with SITL drones, you can consider reducing the rate a bit at which they blast out MAVLink messages.