Python API for the Chromation spectrometer dev-kit
microspeclib is a Python API for the Chromation
microspec project also includes:
- command line utility
microspec_cmdlinefor running basic measurements without developing a Python application
- an emulator (Mac and Linux only) for faking the dev-kit hardware in unit tests
The Chromation spectrometer is a surface-mount PCB package consisting of a linear photodiode array and optical components.
The Python API communicates with firmware on the two microcontrollers in the dev-kit, one on each of the stacked PCBs.
- The microcontroller on the bottom of the stack provides a SPI interface to the Chromation spectrometer.
- The microcontroller on the PCB stacked above provides a USB bridge that turns the SPI interface into a USB interface.
microspeclib accesses this USB interface using
Install the Python API
microspec project with
$ pip install microspec
To extend/customize/repurpose the API, clone the repository from
the project homepage:
https://github.com/microspectrometer/microspec and install in
Windows Load VCP
On Windows, when connecting the dev-kit for the first time:
- Open Device Manager:
- right-click on USB Serial Converter
- select Properties
- go to tab "Advanced"
- check "Load VCP"
- cycle power to the dev-kit (unplug/plug the USB cable)
Now "Load VCP" is enabled every time the dev-kit is connected to this Windows computer.
If "Load VCP" is not enabled,
pyserial cannot communicate with
the dev-kit and
microspec will report that it does not see a
connected USB device.
Install extra requirements for testing and documentation
Developers may want to install additional packages required for running unit tests and rebuilding documentation.
- Unit tests require
tabulate. Install these by adding
$ pip install microspec[test]
- Many unit tests use the emulator. The emulator requires
psutil. Install this by adding
$ pip install microspec[emulator]
The emulator also requires the utility
socat, which is only
available for Mac and Linux.
- The documentation is built with Sphinx. Developers extending
the API will need to rebuild the documentation. Install the
Sphinx-related requirements by adding
$ pip install microspec[dev]
Use the Python API
Import the API in a Python script or at a Python REPL:
>>> from microspeclib.simple import MicroSpecSimpleInterface
The API is a set of commands for configuring the spectrometer and acquiring data.
There is one method for each command. Commands are
camelCaseFormatted. Commands return the received reply object. If
there is an error or a timeout, the reply is
The following will connect to the dev-kit USB hardware, capture a single frame, then print the status, number of pixels, and the value of the 3rd pixel.
from microspeclib.simple import MicroSpecSimpleInterface si = MicroSpecSimpleInterface(timeout=2) reply = si.captureFrame() print(reply.status) print(reply.num_pixels) print(reply.pixels)
Command Line API
microspec_cmdline.py executable will run a single command
and print the reply to stdout, optionally in CSV format. The
default is to look for hardware, but -f FILE can be used to point
it to either a device file or the name of a port, as in "COM3",
if necessary. The command itself is case-insensitive, and after
the command are key=value pairs of options for the command, if
necessary, such as
The -t timeout is how long it will wait for the command each time, and if it fails it will print None and move on. If a -r repeat is specified, it will run the command that many times. And if it is repeating, a -w wait will wait that long in between commands. All times are in fractional seconds.
For example, to set the exposure and cycles and then get 3 capture frames spaced 1.5 seconds apart, with a timeout of 0.2 seconds on each, and print it in CSV format:
microspec_cmdline.py setsensorconfig binning=true gain=gain1x row_bitmap=0x1f microspec_cmdline.py setexposure cycles=100 microspec_cmdline.py captureframe -t 0.2 -r 3 -w 1.5 --csv
The command line utility is a
.exe on Windows
On Windows, replace
microspec_cmdline.py in the above lines
> microspec-cmdline.exe captureframe -t 0.2 -r 3 -w 1.5 --csv
Emulate hardware with
Note that if you have no hardware connected, you can (on Linux and MacOSX) add a "-e" flag to use the emulator. It won't return very interesting capture frame data, but it will give an opportunity to test the interface.
For now, this is only supported on Linux and MacOSX, and requires
socat executable to be installed and available on your PATH.
Use the emulator with the command-line utility by adding a "-e" flag.
Use the emulator with the
microspeclib.expert API with keyword argument
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