Trying to understand ExpressLRS/ELRS and Mavlink

I’ve been trying to understand the features and limitations of ExpressLRS and Mavlink. Currently using ExpressLRS 3.2, Radiomaster TX16S/EdgeTX 2.8, Arducopter 4.4.

  1. I know I get Mavlink messages via Yaapu, but no way to get real Mavlink protocol out (i.e. via USB/UART/TX Backpack). I can get generic telemetry out to a telemetry viewer but not Mission Planner. As I understand it, ExpressLRS is only receiving and outputting to Yaapu generic telemetry?

  2. Is the only way to even get one-way (receive) Mavlink that is compatible with Mission Planner, to use a separate TX/RX module? Not currently needing two-way (i.e. control, mission upload, etc), just wanting receive.

2a) If so, since there is no timeframe for full Mavlink support in ExpressLRS, what is the cheapest/lightest way to obtain one-way Mavlink receive to use in Mission Planner?

There is no mavlink via Yaapu script … Yaapu only uses CRSF with ExpressLRS.

There is currently no Mavlink with ExpressLRS. If it will ever come is uncertain, because not important for the ExpressLRS project.

There is no light and cheap equipment to transmit Mavlink more than a few km. You could at most play a new firmware on your transmitter to generate there Mavlink. Klick!

There is no light and cheap equipment to transmit Mavlink more than a few km

I beg pardon, but this is not correct:

2 x 15$ = 30$ for a tx and rx (DIY) module

crsf, yaapu, ardupilot, mavlink, mission planner, all there:

=> statement not correct at all :slight_smile: :slight_smile:


Olli, I know your projects … But there are no easy and cheap modules that you can just buy ready-made. With DIY is of course much possible, but I think that was not asked.

Personally, I am also bothered by the fact that mLRS hardly has a community. I believe everything you write, but it is also so that exactly only one person develops the system. If you have no problem with it as a user, everything is fine …

I guess I miscommunicated, I am referring to the boot/error messages that stream in the Yaapu script (I called Mavlink messages because they say Mavlink).

A few km would be fine for me at this point. I said cheapEST and lightEST as a comparison to all that is available.

I know the ExpressLRS devs are highly resistant to adding Mavlink support, however the more we use it in whatever roundabout way, maybe they will be more likely.

I have been looking at this but I do not have a separate TX to run only mLRS right now nor do I want to mess with the DIY stuff on an expensive LR drone (yet, lol). It would be WONDERFUL if this could run on existing off-the-shelf modules, then I could at least just convert existing and maybe have an extra TX module to swap in, but sounds like that will never be the case due to hardware differences?

Hi Reinhard,

Have you seen this one?
ELRS Airport (with MAVLink flow control)

It’s just a start. I keep my fingers crossed.

Hi Bryan,
Even if its not Olli’s most favorite platform, you can run “mLRS” firmware on off-the-shelf FrSky R9 hardware right now.

Hi Sascha,
I guess we will have to wait and see. IMHO this is also not a bi-directional Mavlink. I myself tend to separate RC and Mavlink connection, so far I have made good experiences.

Hi Reinhard,

The ELRS fork listed above is a MAVLink flow control on top of a transparent bidirectional serial link. The application is to use a second set of rx and tx to transport MAVLink data (in both directions).

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Oh, I may have to look into that! I’m not a fan of FrSky either but may have to just do it instead of waiting for the slight chance of it happening with ExpressLRS.

I was looking into this as well, but I saw a lot of comments about it not playing well with the same band RC link (i.e. 2.4 RC and 2.4 Airport), and I think even some that it caused issues even with different bands.

@olliw42 Hello.
I’ve tried 915MHz multiple pairs of Mlrs digital transmissions working together at the same time signal quality is very poor with interference;

I have tried to modify the ID and frequency range, the signal quality is very good when the digital transmissions are close to each other, and very poor when they are a little farther away. (It’s mainly interference between pairs. Disconnecting one pair of pairs restores the signal)

Is there any other way I can minimize the interference when multiple MLRS pairs are working at the same time?

The only way to prevent interference would be to have coordinated transmissions and frequency hopping so transmissions don’t step over each other or swamp out the incoming transmission.

I don’t think those tiny RF modules would support using circulator to separate transmitters and receivers. You would also need to match the antennae so the SWR is as low as possible.

The easiest way to reduce interference would be to use two circularly polarized antenna with opposite polarizations if you can find