Mavlink serial ports limited to 4 even on H7 boards

Development Team
1

is there any specific reason mavlink is restricted to just 4 serial ports? I have just built my rover around mavlink to discover that you can only use it on 4 ports

Im curently running

mavlink hoverboard motor controller,
mavlink AI camera,
Mavlink Lidar,
8266 wifi adapter
mavlink UHF telemetry
mavlink monitoring computer

as soon as i enable more than 4 ports one stops working.

2

It might be related to MAVLINK_COMM_NUM_BUFFERS which is 4 by default.
https://mavlink.io/en/mavgen_c/#channels

1 Like
3

I would say that is a scheduling issue. Mavlink in/out is handled from the main thread so it could be a burden to the main loop scheduling if there is too much mavlink routing involved.
There should be indeed : MAVLINK_COMM_NUM_BUFFERS == 5 mavlink port working (usb will take one by default).

Good question anyway as H7 should “theorically” be able the handle more than F4.
Notice that MAVLINK_COMM_NUM_BUFFERS was extented to 7 with networking enabled, so the limit could problably be raised

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4

I tried enabling ppp but it’s still limited to 5 on the serial ports.even if they were rate limited it would work fine for me as only 1 of them is a high speed device the rest is just sensors that send back at 1hz.

I have had to get creative, I have multiple devices connected to the serial 1 TX pin at 115200 so they can all get data at 115200 then im using a RP–2040 to buffer the data back to the flight controller to a different port that runs at 1500000 so it doesnt get overloaded. because all mavlink packets get sent to all the ports it still works.using TX and RX on 2 different ports.