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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        • 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 Michael,

            is there any progress in development of this useful software? Sharing would be great and would allow further branches.  

            I loaded the hexfile into a arduino uno connected on pixhawk running 3.3.2. Flight modes are shown on MC32 but no other data. As soon as I get a pro mini board, I will start new tests. 

            Do you have experience with new pixhawk firmware versions?

            The APM version was running perfect and delivered all data to the MC32 Display, but I changed all flightcontroll to pixhawk.

            Thanks for all things done. 

            • Thank you for your testing with MC series RC which I don't have.

              I use this with my pixhawk's latest FW with no problems.

              Newer version will use better-written 1-wire serial port, but it's not ready yet.

              Will be glad to hear form you.

              • Maybe I found my issue while try to get this code running:

                • My mistake was to use the minimosd connector to supply the arduino board with mavlink data. Minimosd is connected to telem2 - didn´t doublecheck if it worked after the last updates.
                • While debugging the code, I found heatbeat and flightmode but no other. 
                • Then found this description: 
          • 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 ?

            • Hi,

              "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.

  • 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)


    3701993504?profile=original3701993554?profile=originalTwo 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.

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