Good day guys !!  

I feel the need to obtain the information from my PixHawk in my Graupner MZ-24 screen. I found
some threads talking about a change in arducopter firmware to run the telemetry, not good at messing original controller firmware.

Then I found an "adapter" that staff of the AutoQuad made to convert the MavLink in Hott telemetry.

I come here to share a few changes I made in the project Mav2Rott downloaded here:
This is an adaptation to send the telemetry PixHawk for Graupner Hott Protocol.

Is correct with some features:

Battery Voltage;
Altitude for barometer;
Satellite count Speed;
Flight Modes Current drawn by the motor;
Direction of the Head;

I am not able to make it work:

Correct display Latitude and Longitude;
Distance of Home;
Direction of Home;

If anyone can help thank you very much.
The project is attached to the topic. The connections are equal to the jd-ioboard. I am using an Arduino Pro Mini.

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Good morning guys

I'm sending firmware update to make the conversion MavLink ( Arducopter ) for Telemetry Hott .

It's working for now :

Altitude ( Baro )
Speed ​​( GPS)
Battery Voltage
Battery current drain
Distance to Home
Bearing to Home
Satellite count 
Flight Modes
Direction of the Head; 

Thanks for sharing!

I will try it as soon as my new AUAV-X2 arrives (small pixhawk comp. controller board).

I'd like to suggest my version of MAVLink2HoTT adapter for testing/usage. Any feedback and ideas are highly appreciated.

This code is based on my HoTT telemetry patch for APM which is based on Adam Majerczyk code.

This code displays every parameter provided by MAVLink and HoTT:


Absolute air pressure


Climbrates by 1s, 3s and 10s



Battery capacity used

Battery percent used

Ground speed

Fuel in ml shows used mAh

Electric time shows time when current is above 2A

Flight direction (not heading, but movement direction)

GPS satellites number

GPS fix type

GPS coordinates

Yaw, Pitch and Roll in degrees

Home distance

Home direction

Armed / Disarmed status

Flight mode

Current WP number in AUTO mode

Heading and distance to current WP

MAVLink heatbeat status

Throttle (shown in RPM field)

Two HEX files are compiled for any Atmega328 16 MHz controllers with different pins for HoTT communication.

Controller LED shows status:

1 short flash -- bootloader started

5 short flashes -- initialization passed

3 short + 1 long flashes -- MAVLink streams request sent

Slow blinking (1 blink in several secs) -- MAVLink stream is being read, but no HoTT communicaton

Faster blinking -- HoTT communication active.

When both MAVLink and HoTT communications are active LED blinks in faster irregular manner.

Here are HEX files.

This code was tested on funduino pro mini controller with Graupner GR-12, GR16 and GR-20 receivers.

RCs used in tested were Graupner MX-16 and MX-20.

I'll appreciate feedback from owners of MC an MZ series RCs as I'm not able to test this confuguration.


Hello Marcelo!

I tested your sketch yesterday. Works!

One thing i noticed is the heading. It must be sent in 2 degree steps. I get a heading from~ 1-140°

Hello Michel!

How can i flash the hex file to my Pro mini? Do i need a special ISP?


You don't need any ISP. As these boards usually come with bootloader already installed, so you don't need any ISP, only serial port (eg. FTDI cable etc).

Just use google search how to flash hex into arduino board. It's easy. If you have serial cable (and you should have if you are able to test and flash sketches), use it with AVRDude, which you should also have installed with arduino IDE.

There are several free GUIs for AVRDude on the net.

Friend , I was dedicated to improve my Drone flight time just leaving it to the background , I was very interested in your code will test and see how it behaves .

Hello Michel,

I'am testing and i'd like to have failsafe indication (battery, ...), fence breached ...  with message and sound on my mx20.

Did you develop it ? Could you share your code ?


Hi pix,

Yes I developed this code based on Adam Majerczyk's and MinimOSD code.

I plan to share it, but nowadays it doesn't look good enough.

What features exactly do you need?

In fact it's possible to display a string of text at the bottom of MX-20 summary screen (I display flight mode text there) and trigger alarm.

There is battery voltage indication and also battery low alarm which is autocalibrated at power-on assuming battery connected is not exausted.

If you know how to get fence breached info from mavlink stream, tell me and I'll implement this feature.

Also if fence guard is enabled you'll see flight mode changed when autofence is triggered.

Hi Michel,

Thanks a lot for your reply.

I needed to have alerts like onto Mission Planner

But my  first problem is the refresh rating on my mx20.

Did you note this pb too ?


"I want it all and I want it now" approach won't suit here.You should think definitely what alerts do you need and how these alerts are to be displayed.

Please note that MX20 sensor data pages layouts you're using are pre-defined by Graupner firmware and cannot be altered. I tried to make use of all available fields. If you have ideas, you are welcome. There is also so-called "text mode" in HoTT specs, which allows to write any alphanumeric data to RC display, but it works even more slowly and is not recommended by Graupner to be used in-flight, only during setup. (Receiver setup pages use this mode and you may see slow update yourself).

What problem with refresh do you have? A delay of 1-2 seconds is normal for HoTT telemetry as RC polls sensors (which are emulated by my code) at that rate. If you select "Receiver" in MX20 HoTT display menu, you'll see it updating at same rate.


Yes, and as usual, coffee too.

Seriously, good job Michel.

l'll come back later. 

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