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CdF Plasma Controller

Raspberry Pi-based PWM controller for plasma tubes that support the Open Sound Control (OSC) protocol.

Installation

On the Raspberry Pi

Clone the repository.

cd ~/
git clone [email protected]:coup-de-foudre/cdf-plasma-controller.git
cd cdf-plasma-controller/

Install python3 with pip and the requirements

We require Python3 and pip, which you have to install:

sudo apt-get update && sudo apt-get install -y python3-pip
sudo pip3 install -r requirements.txt

Install pigpio from source and start the daemon

The CdF Plasma Controller requires the pigpio installation, and in particular, the pigpiod daemon should be running. To install the pigpio driver on a Raspberry Pi, run

wget https://github.com/joan2937/pigpio/archive/V67.tar.gz
tar -xf V67.tar.gz
cd pigpio-67
make
sudo make install

You then need to start the daemon using

sudo pigpiod

Running the daemon on startup

To have the daemon run on startup, first cd into the pigpio-67 directory above and then run

cd util/
sudo cp pigpiod /etc/init.d/pigpiod
sudo chmod +x /etc/init.d/pigpiod
sudo update-rc.d pigpiod defaults
sudo service pigpiod start

You can now start, stop and restart the pigpiod service using the commands

sudo service pigpiod start
sudo service pigpiod stop
sudo service pigpiod restart

See the README.md here for more details.

Note If you installed the older version of pigpiod using apt-get, you may need to unmask previous service using sudo systemctl unmask pigpiod. (You can check if it's masked using sudo systemctl status pigpiod.)

On a client machine external to the Raspberry Pi

If you want to run over a network, you'll need to have Python 3.4 or greater (preferably 3.6) and pip3 installed on the client machine. (Google it.) Then clone this repo and run

sudo pip3 install -r requirements.txt

You should now be able to connect to a remote Raspberry Pi running the pigpiod daemon.

Running

There are two ways to control the PWM, either via the keyboard or using the Open Sound Control protocol. The next two sections provide examples of using it both ways.

For the full range of options, see ./plasma_controller.py -h.

Using the keyboard

The simplest way to use this package is via the keyboard controller, which allows you to change the parameters using key strokes. If you have this package installed on a Raspberry Pi following the directions above, try running the PWM with an initial frequency of 10000 Hz:

./plasma_controller.py -f 10000.0

You'll see a screen that looks like this:

Keyboard

Use the specified keys to increment or decrement the parameter values.

Using Open Sound Control (OSC)

This package also allows control of the PWM via the Open Sound Control (OSC) protocol.

To enable OSC, setting the --controller-type=OSC flag on the command line. This starts a OSC server on UDP port 5005 with the following endpoints:

  • /pwm/start Start the PWM, but does not turn on the interrupter or the FM modulator.

  • /pwm/stop Stop the PWM Also turns the interrupter and FM modulator off.

  • /pwm/toggle <value> Toggle based on the value of the argument. No argument or a "falsey" value turns stops, while a "truthy" value starts.

  • /pwm/center-frequency <float> PWM center frequency in Hz. Resets the fine control value to zero.

  • /pwm/fine/spread <float> Set fine control frequency spread around the center frequency

  • /pwm/fine/value <float> Set fine control frequency value. Value is capped between [-1, 1]. The true frequency is given by

    center-frequency + value * spread

    where spread is set with /pwm/fine/spread.

  • /pwm/frequency-offset-factor <float> Offset factor for the center frequency. Should be between [-1, 1]. The true frequency is given by

    center-frequency * (1 + offset-factor)

    This simplifies implementing small changes of the input frequency around a fixed center frequency.

    Use of this endpoint immediately stops the FM modulator.

  • /pwm/duty-cycle <float> Set the PWM duty cycle. Settings other than 0.5 (the default) create a DC offset in the output, which may damage some circuit configurations.

  • /pwm/fm/start Start FM modulation.

  • /pwm/fm/stop Stop FM modulation.

  • /pwm/fm/toggle <value> Toggle based on the value of the argument. No argument or a "falsey" value turns stops, while a "truthy" value starts.

  • /pwm/fm/spread <float> Set the PWM FM spread in Hz.

  • /pwm/fm/frequency <float> Set the PWM FM frequency in Hz. Use of this endpoint starts the FM modulation.

  • /pwm/interrupter/start Start the interrupter.

  • /pwm/interrupter/stop Stop the interrupter.

  • /pwm/interrupter/toggle <value> Toggle based on the value of the argument. No argument or a "falsey" value turns stops, while a "truthy" value starts.

  • /pwm/interrupter/frequency <float> Interrupter frequency in Hz.

  • /pwm/interrupter/duty-cycle <float> Interrupter duty cycle in Hz.

The default root /pwm/ is configurable for adding new channels via the --osc-roots parameter.

You can test OSC using the included osc_msg.py script. You can test that the server is receiving messages as follows:

# On RPi on localhost, local network address 192.168.2.247
./plasma_controller.py --controller-type OSC -vv -f 10000

# In a separate terminal screen same RPi
./plasma/utils/osc_msg.py /pwm/center-frequency 10001

# On another machine on the local network
./plasma/utils/osc_msg.py --server 192.168.2.247:5005 /pwm/center-frequency 10001

If it's successful, you should see output that looks like the following:

DEBUG:controller.osc_controller:{'offset_factor': None, 'center_frequency': 10001, 'osc_path': '/pwm/center-frequency', ...}

Note The server only supports OSC over UDP. If you have difficulty receiving messages, make sure that your client is configured to use UDP, not TCP.

Additional Examples

  1. Run in interrupted mode, with the interrupter running at 100Hz and 30% duty cycle.

    ./plasma_controller.py -F 100 -D 0.3 -f 30000

    NOTE Running interruption over a network is not recommended, since network latency will significantly affect the interruption rate.

  2. Control the RPi at address 192.168.2.247 on pin 12 at 15kHz.

    ./plasma_controller.py --pin 12 --host 192.168.2.247 -f 15000

  3. Start an OSC controller with initial frequency of 83.3MHz with root pwm1 and verbose logging:

    ./plasma_controller.py --controller-type OSC -f 83300000 -r pwm1 -vvv

Copyright and License

Copyright 2018, Michael McCoy <[email protected]>

This file is part of the CdF Plasma Controller.

The CdF Plasma Controller is free software: you can redistribute it and/or 
modify it under the terms of the GNU Affero General Public License as 
published by the Free Software Foundation, either version 3 of the License, 
or (at your option) any later version.

CdF Plasma Controller is distributed in the hope that it will be useful, 
but WITHOUT ANY WARRANTY; without even the implied warranty of 
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero
General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with the Cdf Plasma Controller.  If not, see 
<http://www.gnu.org/licenses/>.