Gpredict and Arduino rotor project


Have made a home built rotator project from: by Julie VK3FOWL & JOE VKEYSP. Win install is under the heading “Windows Installation” on this page.

The portable rotator project really works well for portable operating. As the Ardueno project is designed, it can only work with Gpredict up to and including ver. 1.4. After that It will not work properly. I assume because of Hamlib Rotctld Easycomm II protocol??? Maybe the feedback positioning of the rotator?? Not sure??

I do not know the exact reason it will not work with later versions. I would really like to use the latest release of Gpredict In the project if possible. It still works great with Ver. 1.4.

I am using a Win10 machine, Hamlib, Rotctld, Easycomm II protocol for the rotor control function.

Any guidance or help is sincerely appreciated.


Hi Ed,

I think this is an issue that has been fixed since the last release, see issue #128, so please stay tuned for the next release b the end of the year, I hope.

In general, please always try to describe the error or malfunction you are experiencing. In most cases, we don’t have access to the same hardware and only knowing that it is not working properly is not enough information. The diagnostic messages under File -> Log browser can often provide useful information.


Hi Csete,
Thank you for taking the time to answer me. The problem sure seems to be the same as described in issue#128, after going through the emails.
I have no means other than use the program and give the results.
This is the bat file that is run before opening Gpredict:

cd \Program Files (x86)\hamlib-w64-3.2\bin
cmd /k “rotctld -m 202 -r COM11 -s 9600 -T -t 4533 -C timeout=500 -C retry=0 -vvvvvvvv”

Ver. 1.4 works perfect with tracking and manual control of the rotor.

Gpredict log file 1 entry with manual control only with engage button, 2nd tracking and 3rd tracking also:

2018/09/13 09:17:03|3|sat_log_init: Session started
2018/09/13 09:17:03|4|sat_cfg_load: Everything OK.

2018/09/13 09:52:01|3|sat_log_init: Session started
2018/09/13 09:52:01|4|sat_cfg_load: Everything OK.

2018/09/13 11:24:24|3|sat_log_init: Session started
2018/09/13 11:24:24|4|sat_cfg_load: Everything OK.

Sequence to use Gpredict:
Run above BAT file.
Start 2.2.1
Select->Rotor control
Press->Engage(no tracking) Target
In the Rotor Control window The feedback readings for Azimuth & Elevation are correct
At this point the program freezes up. If I tap the upper right hand close X in the
Rotator Control window, a few times the Rotator Control window will close.
Gpredict main program is still frozen up, press the upper right hand corner close X (then (Not Responding) shows up. Continue to press the X and the Widows dialogue comes up with the “restore” “close” “Wait” selections. I can keep pressing the Red X or use Windows “Close” option and Gpredict closes.
As soon as Gpredict closes, the settings that were entered into the Rotator Control window either by “tracking” or by just engaging the settings without “tracking” and pressing “Engage”, at this point the rotator moves to the correct azimuth and elevation positions. This happens every time, without exception.

I wish I had the tools to update with the code from the issue#128, but sadly I do not.
Any chance of getting hold a a beta? Know you are busy with real life, and just a question about a beta.

Again thanks for your time and answer.

Hopefully this information helps.


Big fingers.

Not as long as I have to make the binaries. You have to understand that the whole point with gpredict was to make a satellite tracking application for Linux. Windows support will never have any priority in my life, sorry.


Totally understand. Just a question.

Thanks for a great program.

Have a nice evening.


I built the same Rotator one with DC motors and one with AC motors. They both work perfectly with Gpredict 2.2.1. on Linux Mint. The build instruction do mention of a coms problem with Windows and I think they also supplied a solution. Go back and read the whole article. I can’t remember the details.
73 vk2byf