Raspberry Pi Satellite Rotator Interface

We’ve been using our Portable Satellite Station 2.0 for some time now, and it works great. One area that can be improved is the interface between the MacDoppler Satellite Tracking program we use and the GHTracker application, which controls the Green Heron Engineering RT-21 Az/El Rotator Controller in our setup. Our initial approach was to run the GHTracker app under Windows/VMWare on the same MacBook Air laptop that runs MacDoppler. While this approach works ok, it was more complex and less reliable than we had hoped.

Fortunately, MacDoppler and GHTracker use a UDP-based interface that will run over an IP network.

Anita, AB1QB, got great results using a Raspberry Pi 2 with a Touch Screen for her DX Alarm Clock Project, so I decided to do something similar with GHTracker. The new Raspberry Pi 3 Model B boards feature a built-in WiFi networking interface and four USB ports, making the RPi 3 a perfect platform for this project. An email exchange with Jeff at Green Heron Engineering confirmed that GHTracker could run under Linux on the Raspberry Pi (RPi).

We wanted a compact package that did not require anything but a power supply to run the final project. There are many great parts available for building a Raspberry Pi system. Here’s what we used:

• Raspberry PI 3 Model B 1.2GHz 64-bit quad-core ARMv8 CPU, 1GB RAM
• Samsung 32 Gb Class 10, UHC-1 MicroSD Card
• PiTFT Plus 480×320 3.5″ TFT+Touchscreen Display
• Pibow PiTFT+ Case for Raspberry Pi
• Black Aluminum Heatsink Cooler Cooling Kit for Raspberry Pi 3
• CanaKit 5V 2.5A Raspberry Pi 3 Power Supply

The total cost for all of the parts was $120.

The assembly of the case and the hardware was straightforward. The folks at Adafruit provide a pre-built Jesse Linux image for the RPi, including the necessary driver for the Touch Screen Display.

After some configuration work and creating a few shell scripts to make it easy to boot the RPi to an HDMI display or to the Touch Display, we were ready to install the GH Tracker App. We also enabled the VNC Server on the RPi to use a VNC Client application on our MacBook Air instead of directly connecting a display, keyboard, and mouse to the RPi. Finally, we installed Samba on our RPi to allow files to be moved between our other computers and the RPi.

Jeff at Green Heron Engineering provided a copy of GHTracker V1.24 and the necessary serial interface library to enable its use on the RPi. Jeff is planning to make a tar file available with GH Tracker and the library in the near future. We did some configuration work on LXDE (the GUI interface for Linux that runs on the RPi), and it automatically runs GH Tracker whenever the RPi is booted up. We also optimized the GUI for the sole purpose of running GH Tracker on the Touch Screen Display. Finally, we configured the Ethernet and WiFi interfaces on the RPi to work with our home network and LTE Hotspot modem.

With all the software work done, it was time to test the combination with our Satellite Rotator System. The setup worked on the first try using a WiFi network connection between the MacBook Air Laptop running MacDoppler and the RPi. The USB-based serial ports, which control the Azimuth and Elevation direction of the rotators, worked as soon as they were plugged into the RPi. Also, the touchscreen interface works well with the GH Tracker App making the combination easy to use.

The VNC Client/Server combination allows us to work with the software on the RPi right from our MacBook Air laptop. It also makes for a nice display for monitoring the GHTracker App’s operation from the Mac.

You can find information about how to build your own Raspberry Pi Satellite Rotator Interface here.

Other articles in the Portable Satellite Station series include:

• A Portable Satellite Station Part 1 – A Simple Station for AO-85
• A Portable Satellite Station Part 2 – 2.0 Station Goals and Antenna System
• A Portable Satellite Station Part 3 – Station Radio and Supporting Equipment
• A Portable Satellite Station Part 4 – 2.0 Station First Contacts!
• A Portable Satellite Station Part 5 – Plans for Our 3.0 Station
• A Portable Satellite Station Part 6 – 3.0 Station Initial Contacts
• Raspberry Pi Satellite Tracker Interface How To
• Plans for Upgrading Our 2.0 Station for ARISS Contacts
• PTT Router for Satellite Station 3.0

You may also be interested in the satellite station at our home QTH. You can read more about that here.

Thanks to the help from Jeff at Green Heron Engineering, this project was very easy to do and worked out well. The Raspberry Pi 3 platform is powerful and relatively easy to work with. It makes a great start for many Ham Radio projects. Also, there is a wealth of online documentation, how-to information, and open-source software for the RPi. I hope that some of our readers will give the RPi a try!

Fred, AB1OC