Greenctld is a driver that enables hamlib and SatNOGS to communicate with the Green Heron Engineering RT-21 Rotator Controller. The GAS Team has made several modifications to the original repository. For use with the GASGroundStation code, Raspberry Pi 4, and Alfa Spid RAS Az/El rotator, the installation instructions below must be followed. All changes made by cartertpage and jackadanos.

• GAS Team Changes
• Installation Instructions
• Configuring udev Rules
• Rotator Controller Settings
• Adding make-run.sh to the Crontab
• Manually Commanding the Rotator
• Rotator Controller Settings
• Original README
  • Usage
  • License

• make-run.sh, cron job bash script that ensures greenctld is always running

• gasctld-log.txt, status output from make-run.sh

• requirements.txt, for easy installation of the dependency Python 2.7 package pySerial

1. Clone the repository:

   git clone https://github.com/SmallSatGasTeam/greenctld.git

2. Rename the "greenctld" directory to "gasctld":

   mv greenctld/ gasctld/

3. Install Python 2.7:

   sudo apt install python2

4. Install pip2:

   curl https://bootstrap.pypa.io/pip/2.7/get-pip.py --output get-pip.py

   python2 get-pip.py

5. Install dependencies:

   pip2 install -r requirements.txt

The rotator controller connects to the Raspberry Pi using two separate USB cords. When the Pi boots up, it assigns the two cords specific device paths (/dev/). If we do not create udev rules, the device paths could change randomly. Creating the udev rules will ensure the azimuth cord is always on /dev/azimuth and the elevation cord is always on /dev/elevation.

1. On the rotator controller, turn the knobs to set the azimuth to 180 and the elevation to 0.
2. The two cords will usually be /dev/ttyUSB0 and /dev/ttyUSB1 (or /dev/ttyACM0 and /dev/ttyACM1. If so, adjust the following accordingly).
3. Run through Manually Commanding the Rotator using ./greenctld --az-device /dev/ttyUSB0 --el-device /dev/ttyUSB1 for step 1.
4. Run the "Get Position" command. If your output is:

   • P 180 0, we guessed the device paths correctly, therefore azimuth = /dev/ttyUSB0 and elevation = /dev/ttyUSB1.

   • P 0 180, we guessed the device paths incorrectly, therefore elevation = /dev/ttyUSB0 and azimuth = /dev/ttyUSB1.

In order to write the udev rules, we must determine each cord's serial values, which are one of the only unique identifiers between the two.

1. For this, we will assume that azimuth = /dev/ttyUSB0 and elevation = /dev/ttyUSB1. If yours are the other way around, adjust the following accordingly.
2. Run the following commands to determine the serial values for each cord. The first is for /dev/ttyUSB0 and the second is for /dev/ttyUSB1. The output of each should look like ATTRS{serial}=="AB0N4HB4", along with some other rows. Be sure to write down the value "AB0N4HB4" and note for which cord it is for, as we will be using that number in the next section.

   udevadm info -a -n /dev/ttyUSB0 | grep serial
   

   udevadm info -a -n /dev/ttyUSB1 | grep serial
   

1. Open a new file in the udev directory.

   sudo nano /etc/udev/rules.d/99-usb-serial.rules
   

2. Copy and paste the following lines, replacing XXXXXXXX with the appropriate serial values we determined in the previous section.

   SUBSYSTEM=="tty", SUBSYSTEMS=="usb", DRIVERS=="usb", ATTRS{serial}=="XXXXXXXX", SYMLINK+="azimuth"
   SUBSYSTEM=="tty", SUBSYSTEMS=="usb", DRIVERS=="usb", ATTRS{serial}=="XXXXXXXX", SYMLINK+="elevation"
   

3. Exit and save the document.

1. Reload the udev rules.

   sudo udevadm control --reload-rules
   sudo udevadm trigger
   

2. List our new udev rules. If they are not found, then you have a problem! If they are listed, you did it! The two USB cords should now reliably connect to /dev/azimuth and /dev/elevation.

   ls /dev/azimuth /dev/elevation
   

The settings the GAS Team uses for the RT-21 controller with the Alfa Spid RAS rotator are as follows:

Calibration = 180 (displayed number should be aligned with actual direction of antenna)
Offset = 0
Delays = 0
Min Speed = 3
Max Speed = 10
CCW Limit = 181
CW Limit = 179
Option = SPID
Divide Hi = 360
Divide Lo = 360
Knob Time = 40
Mode = NORMAL
Ramp = 3
Bright = 1

1. Open the crontab:

   crontab -e
   

2. Copy and paste the following two lines. The first will run greenctld at reboot, and the second will run make-run.sh every five minutes.

   @reboot ./gasctld/greenctld --az-device /dev/azimuth --el-device /dev/elevation
   

   */5 * * * * ./gasctld/make-run.sh
   

3. To ensure greenctld is running, you should be able to run htop and see the process /usr/bin/python2 ./gasctld/greenctld --az-device /dev/azimuth --el-device /dev/elevation running.

The following can be used to manually command the rotator from a command line. You should only expect to use this in testing/troubleshooting.

1. If greenctld is not running, run the script:

   ./greenctld --az-device <az serial port> --el-device <el serial port>

   If you do not yet know <az serial port> and <el serial port>, you should probably run through (Configuring udev Rules)[#configuring-udev-rules] first.

2. From a separate terminal, connect to the rotator controller's port:

   nc localhost 4533

3. The following commands can now be run:

   • Get position: p (lowercase p)
   • Set position: P <Az> <El> (uppercase P)
     • Example: P 150 20 sets the Azimuth to 150 deg and the Elevation to 20 deg.
   • Halt movement: S (uppercase S)

A hamlib-compatible driver for the Green Heron Engineering RT-21 Digital Rotor Controller. hamlib does not support the rotor, but this program can be used as a drop-in replacement for rotctld when commanding the RT-21.

The RT-21 is unlike most of the other rotors hamlib supports in that it uses two serial ports, one for controlling azimuth and one for controlling elevation. The two serial ports are passed via the --az-device and --el-device command line arguments.

The TCP network protocol is compatible with the hamlib protocol documented in the rotctld(8) man page. This driver only implements a subset of that protocol, which includes the subset that gpredict uses. At Astro Digital, this driver has been used extensively with gpredict. For debugging the network protocol, the --dummy option can be used to simulate a rotor without connecting to a real serial port.

Like rotctld, this program does not daemonize on its own. It also produces copious debugging output to stdout.

• --az-device <serial-port>, the serial port to use for azimuth

• --el-device <serial-port>, the serial port to use for elevation

• --speed <baud>, the serial baud rate to use, defaults to 4800

• --timeout <seconds>, the serial port timeout, defaults to 1.5

• --port <port>, the TCP port to listen for connections on, defaults to 4533, the same as rotctld

• --get-pos, to query the serial ports for the current az/el, and immediately exit. Useful for testing the serial port configuration.

• --dummy, to speak the TCP network protocol only without connecting to a serial port, useful for debugging gpredict integration.

Copyright (c) 2017 Astro Digital, Inc

Released under the terms of the Simplified BSD License; see the LICENSE file for details.

Michael Toren <[email protected]>