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Feb 16, 2020, 11:24 AM
Thread OP

MAVLink for OpenTx and Telemetry Script

Hey Folks,

I think it's time for sharing with you the project I'm working on lately, which is about bringing native MAVLink support to OpenTx.

The FrSky passthrough certainly is a fantastic development, and really has brought new things to the table. For drones I however believe that what one really wants to have is the bi-directionality and comparatively high throughput which is offered by the usual MAVlink wireless links. And that's what this project is about, and that's what this project delivers.

For a teaser please see the attached photo.The videos below provide more information, showing the features as they are available today. You also could inspect the project web page.

Btw, everything you see there is 100% MAVlink. 100.00% MAVLink Standard.

I'd like to acknowledge that the design of the autopilot page of "my" lua telemetry script is much inspired by the Yaapu FrSky Telemetry Script. I also want to acknowledge that the circle drawing code is coming from AdaFruit's GFX library.

Looking forward to your responses and most importantly, have fun guys,

* Github repository for the script and other stuff to download: (all open source under GPL3)
* The source of my additions to OpenTx are found here: I also raised a PR in the main OpenTx repository.

OpenTx with MAVLink: MAVLink Router (18 min 41 sec)

OlliW's OpenTx with MAVLink: Features Update (14 min 36 sec)

Telemetry Script for OpenTx with MAVLink: Features and Capabilities (16 min 28 sec)

Telemetry Script for OpenTx with MAVLink: Hardware (11 min 35 sec)

Telemetry Script for OpenTx with MAVLink: Firmware and Script Installation (8 min 40 sec)
Last edited by OlliW; Feb 14, 2021 at 04:13 AM.
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Feb 16, 2020, 07:59 PM
Registered User
Thanks Olliw for sharing another excellent development.

I guess it's time to open my T16
Feb 16, 2020, 08:30 PM
Thread OP
hey Luis
great to see you're still around

I'm now trying to figure out what the best wireless module would be to combine this with ... there are soo many, ULRS, EZ and family, LORA based and family, or something commercial ... argh ... it would be great if it would be just one antenna instead of two LOL

yeah, the T16 is a bit of a cheapy but is great to tinker with, so, yeah, time to open it ... you should not find it difficult to solder the wires

have fun
Feb 16, 2020, 10:14 PM
Registered User
Out of the top of my head I'm not sure if possibly the multi-module wouldn't be a easier "target", but then we would loose the RC protocol, but piggybacking on the multimodule with the mavlink radio only?
Feb 17, 2020, 05:11 AM
Thread OP
I'm sorry, I don't understand this sentence.
My thoughts go towards wireless links which have combined the bidirectional telemetry and the rc control into "one stream", like what ULRS or EZ-Wifibroadcast has, and I think also some LORA based projects. One antenna for all that data flow.
Feb 17, 2020, 09:27 AM
Registered User
Would this script work if I'm using MAVLink over Crossfire?
Feb 17, 2020, 09:45 AM
Thread OP
I can't say for sure since I don't have crossfire and thus can't test it.

But: I definitely would think so. And, moreover, it definitely should be so!! That is, if it doesn't yet work I should (and would) make it to work. Crossfire is certainly one of the candidate links for which the native MAVLink support aimed at in this project should just work.

The difference to "normal" crossfire would be however that the communication would not go via the pins in the module bay, since this would be only uni-directional but we want to have bi-directionality here. That is the crossfire transmitter module must be configured to output/input rx&tx, and these must be fed to the rx&tx pins on the Jumper T16, as for the SK radio in the hardware video.

In the manual it might be the section "serial bridge" which is relevant. I have set the baudrate to 57600 in the code, which seems to match what crossfire is using in this mode.

The "MAVLink" option may not work, as it appears to be MAVlink V1 only, while you want MAVlink V2.

But as said, I don't have crossfire so don't really know. It simply would need a try, I would say

EDIT: I need to correct, I didn't understood the current TBS/Crossfire serial "bridge" correctly. Crossfire as it currently stands is not suitable for the purpose.
Last edited by OlliW; Feb 18, 2020 at 03:02 PM.
Feb 17, 2020, 04:20 PM
Thread OP
sources of opentx modifications pushed to github repo
Feb 17, 2020, 05:11 PM
Registered User
Hi Olliw, amazing job!
Feb 18, 2020, 12:24 PM
Thread OP
thx, sir
well, let's see how amazing it really should be considered to be
Feb 22, 2020, 07:42 PM
KD2PBU - Fly No Evil
davidbitton's Avatar
hey OlliW, I saw some posts on the DragonLink thread from you. Can a DL TX work with this? Thanks.
Feb 23, 2020, 12:09 AM
Thread OP
I can't say with 100% certainty since I don't have a DL and thus can't test it, but IMHO the DL is a primary candidate for using this !! So the answer should be: YES

to the best of my knowledge DL offers a full duplex transparent serial modem which I think they call "radio modem telemetry", and this would be what is needed here. It might be that the Otx firmware needs some adaption, since in the manual I read it would be better to use 38400 instead of 57600 without flow control, which is what we have here, but that's really all easy.
Feb 26, 2020, 06:28 AM
Registered User
All works! Thank Olliw!
Telemetry Jumper T16 Mavlink olliw42 (0 min 26 sec)
Feb 26, 2020, 07:14 AM
Thread OP
oh, wau, this is fantastic
thx for sharing, much appreciated

btw, I wasn't not working on this in the last days, but in fact improved the otx firmware as well as the script quite significantly I believe. For instance, one can see now the status messages, if available get info on two GPSes, chose the baudrate via the ModelSetup menu, etc., and even added support for scripting guided/autonomous missions.

I hope I can demonstrate the latter by doing a cable cam quick shot, it's all working except of setting the heading of the copter, I somehow can't figure that out since some days now ...

anyway, the bottom line, more to come

may I ask, what telemetry link are you planing to use?
Feb 27, 2020, 03:11 PM
Registered User
I look forward testing this with Dragonlink soon and I definitely like gimbal functions.

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