Enable Serial 5 for Mavlink and Craft and Theory etc [Closed]

Topic: Enable Serial 5 for general purpose use

Proposal type: Hardware [ ] , Software [X] , Other [ ] : _________________

Description:with the number of possible serial devises ever increasing, having serial 5 available would be very helpful.

It is currently the debug console, so a method to change its functionality would need to be sought… and the implications of removing the debug feature would need to be considered.

Planned amount $$ (USD):Unknown (issue is raised… looking for someone to put their hand up

Estimated time for completion: Unknown

relates to issue:


Yes please!
I’ve used the nuttx shell about twice, and most people never will at all. With the number of serial peripherals (gimbals, rangefinders, computers, datalink) now available I think freeing up the use of serial 5 would be awesome.

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Tridge said this should be not too difficult to do…

Craft and Theory would like to throw in $100 to get this developed and approved/merged. Please let me know how to do this so we can give this to the right person.


In linux boot the console is defined in the boot string. Pointing those to dev/null free’s up the port. Then you would need to enable the protocol that C&T uses for that port. Pretty sure that would be easy since its set up for all the other ports just add the port once used for the console. I’ve had to do this on nvidia boards to access all the uarts but not experienced with nuttx.


Tridge has done a pull request!!!

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That’s great to finally hear.

Any ideas when this might migrate into Copter?

not sure, follow the pull request to see when its in master…

Its great! Also if NSH available on any serial port as an option would be the best!

This feature went into the 3.8.1 plane release from today

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That’s awesome tridge! Would you like the payout made out to you or to ArduPilot? You can contact us directly at info@craftandtheoryllc.com.

We’re planning a FrSky telemetry cable for serial 5. It will be in our store soon after we verify that FrSky telemetry works well on serial 5.

Great job and thanks!

Craft and Theory

You don’t need to pay anything, but if you’d like to make a donation to ArduPilot it would be welcome.

One thing to watch out for is that it will get the debug startup messages from NuttX up until the point that ArduPilot reads the SERIAL5_PROTOCOL parameter and changes the port protocol. So you need to test to make sure those bytes at the start don’t cause problems for the frsky adapter. I suspect it will work fine, but make sure you test it thoroughly.
Alternatively, you could use a different UART for FrSky protocol, and then use the serial5 debug port for MAVLink telemetry.

Would very much like to make that donation to ArduPilot. We have been wanting to have serial 5 for quite some time but didn’t know enough to make it work ourselves. We would be very happy to keep supporting the development of some specific features like these from time to time. Thanks again.

I think the startup message shouldn’t be a big problem. Might be a small problem as it means ArduPilot will be talking on the line when other peripherals may already be talking, but that would only happen during startup… so I think we’ll only lose data temporarily and at a time when it doesn’t really matter. But it’s worth making sure there’s no longer term impact. For instance what happens when you turn on the Pixhawk during a sensor discovery on the Taranis… we’ll have to check that. Probably nothing bad, and users should have the Pixhawk turned and done booting before discovery anyways. We’ll see. Thanks for the heads up.

Of course, as you say, people can always connect something else (GPS, MAVLink, rangefinder…) into serial 5 to free up a port for FrSky telemetry.


I need to free my GPS 2 connexion on my copter which is currently used by frsky telemetry. Any news about serial 5 support on Copter?
Thanks for the great job…

It is done in 3.5.4 rc1.


Waow… that’s great.
Thanks a lot!