A Python interface for StellarNet spectrometers designed to provide the functions of a Spectronic 20 spectrophotometer

The goal of this project was to replace the old Spec 20s in our teaching laboratories with equivalent functionality in modern equipment. Choices of hardware and software were driven largely by familiarity. The choice of the Raspberry Pi was to make an effectively disposable computer. I picked Python 3.x (works on Python 2.7 also) for simplicity in migrating to different hardware. What I created here is a simple frontend for the spectrometer suitable for use by relatively untrained undergraduate students.

The project was written to support undergraduate laboratories, so really this repository is for people looking for a frontend to run their spectrometer. However, the functionality of the project can readily be expanded to take advantage of the spectrometer features. This code takes care of collecting the spectra, everything else is just manipulations in code. Simple changes in the code shift the interface from having lots of things chosen for you to needing to make lots of choices.

The master branch only works on Python 3.x, a separate branch has the files for Python 2.7. I wrote this on a Raspberry Pi 3b+. For Windows or Mac you will need to make small changes to the code to deal with OS peculiarities. You will need to possess a Stellarnet spectrometer.

For Raspbian OS, the apt-get package manager is preferred to pip in most cases. For other Linux types, the appropriate package manager (e.g., yum for CentOS) will depend on your Linux distribution.
For Windows and MacOS, one would typically use pip to install Python libraries. Help with pip is available at https://packaging.python.org/tutorials/installing-packages/

• pyusb 1.0.0a3 (Linux python 3 example: sudo pip3 install pyusb==1.0.0a3) this is version specific, so pip is appropriate
• screen (if you want to hide the background processes)
• numpy
• python-matplotlib
• libraries usually automatically included in Python
  • json
  • python-requests
  • python-flask
  • python-virtualenv (if you want to run this in a virtual environment)
  • Tkinter

• 99-local.rules needs to be copied to '/etc/udev/rules.d/' or updated to include rules for StellarNet devices. Otherwise you would need to run as root to get USB access.
• the rest of the files in PiSpec20_stellarnet should go into the same directory
• Issue sudo chmod -x spectroweb.py in the project directory if on a Linux system
• on a Windows system you will need the free 'SWDrivers.zip' or 'SWDriver64.exe' from https://www.stellarnet.us/stellarnet-downloads instead of the driver included in this package
• use the 'run_hidden' bash script to start the project without showing the command line. From the command line issue sudo chmod +x run_hidden to make the bash script executable. On Windows a batch file would substitute the bash script.

• a USB connected StellarNet spectrometer
• a light source if you are going to do absorbance experiments

The following steps were followed to install this project on a Raspberry PI model 3B+ with a fresh Raspbian (full version) installation:

• sudo apt-get install screen
• sudo pip3 install pyusb==1.0.0a3
• downloaded this repository
• from the project directory copied the 'rules' file sudo cp 99-local.rules /etc/udev/rules.d
• change permission sudo chmod -x spectroweb.py
• python3 spectroweb.py will keep this command line window busy, so open another one
• python3 stellarnet_spec.py runs the interface

I don't write in Python for a living, nor particularly do a lot of programming. And it shows in the code.
If you wish to contribute please contact me.

Apache License 2.0. A Stellarnet module is included under the Apache License 2.0, so the whole thing is, too.