trimarlib-sysfsgpio 0.1.0rc2

Sysfs GPIO utility

trimarlib-sysfsgpio

Python GPIO library, using Linux sysfs interface.

Getting started

These instructions will get you a copy of the project on your local machine for development and testing purposes. See Deployment for notes on how to deploy the project on a live system.

Prerequisites

The build process requires some basic development tools:

• make - GNU Make program, either for *nix or Windows system, used to execute build and test targets
• git - used not only to clone the repository, but also in auto-versioning (see Versioning)
• python3

Two standard Python packages are used for build and installation steps:

• setuptools
• wheel

The library has no dependencies on any third-party packages.

Building and releasing

Invoking make all (default target) prepares archives for distribution. It is done in two steps:

1. query Git repository for tags (git describe command) to determine current version and generate version.py file,
2. invoke Python interpreter passing setup.py script to prepare source and wheel distributions.

The Python interpreter invoked by the Makefile defaults to python when running on Windows machine and python3 otherwise. In both cases it is possible to override it passing a PYTHON variable to the command, e.g. make all PYTHON=python3.

The release process is automated and based on GitLab CI/CD environment - each commit triggers a build job which attempts to make and install built packages (no testing implemented yet, requires an available hardware platform). If the commit is tagged the built wheel distribution is passed to the deployment stage and the runner attempts to upload the package to the repository specified in project settings.

Testing

Test source files are located in sysfsgpio/tests directory. Testing is based on unittest Python built-in package. The Makefile defines test target which invokes all tests.

Testing is divided into two steps:

• utility functions testing - performs unit tests of all ancillary features. Those tests are platform independent (i.e. shall pass on either a *nix or a Windows machine);
• Pin testing - performs unit tests of Pin class. Those tests depend on the sysfs Linux filesystem and are skipped when running on Windows machine.

Deployment

The library is not intended to be used in a standalone configuration - the primary purpose is to be used by higher-level applications, which should define it as a dependency. However it is perfectly correct to install it manually using pip.
Please keep in mind that there are some platform dependent steps needed to be taken before the pins are accessible without super-user privileges. The package designates 3 entry points (accessible as command-line tools) to ease-up the set-up process (the scripts are developed and confirmed to be working on Orange Pi platform running Armbian distribution). These entry points are:

• sysfsgpio-install-service - this command installs and enables systemd gpio-exporter service, which exports all free pins available on the Orange Pi SBC at system boot;
• sysfsgpio-install-rules - this command install udev rules file which ensures that each exported pin has rw mode available to staff group;
• sysfsgpio-install - this one invokes the above to reduce number of commands needed to set-up system.

Each of the commands may be invoked with --force switch to overwrite existing files - without that switch commands fail printing proper message.

NOTE: The user needs to become member of the staff group to use the pins without super-user rights.

Versioning

The project is versioned using a simple pattern based on repository tagging feature. See Makefile for implementation details, for versions available see tags on this repository.

Usage

See docstrings for API documentation.

• Example of using pin PA21 as input:

from sysfsgpio import Pin


def callback(sender, value):
    print('pin={}, value={}'.format(sender, value))


pin = Pin('PA21')
pin.direction = 'in'
pin.register_callback(callback)
pin.enabled = True

• Example of using pin PA20 as output:

from sysfsgpio import Pin
import time

pin = Pin('PA20')
pin.direction = 'out'
for i in range(10):
    time.sleep(.1)
    pin.value = pin.value ^ 1

• Example of using pin PA7 as inverted output to generate timed pulses:

from sysfsgpio import Pin

pin = Pin('PA20')
pin.direction = 'out'
pin.config(ontime=3.33, offtime=6.67, repeat=3)
pin.enable()

License

This software is licensed under the MIT License - see LICENSE.