Python API for Numato GPIO Expanders

This Python API can be used to control Numato USB GPIO expander devices with 8, 16, 32, 64, and 128 Ports.

• Configure ports as input or output port
• Write to output ports
• Read from input ports
• Read integer values from ADC input ports
• Register a callback for input port events (edge detection)

See the changelog for details on the releases.

Install uv

Uv is currently by far the fastest and most modern Python project and dependency management tool written in Rust and inspired by Rust's cargo. uv covers the whole Python development environment including but not limited to installation of Python interpreters, dependency-version and package management and transparent isolation in virtual environments. It also enables one-off executions of packages with uvx.

Note:

This readme, only covers the Linux operating system. Refer to the uv documentation to learn how to install and use uv on MacOS or Windows. Keep in mind though that the specifics of device accessibility typically vary across operating systems and numato-gpio is at present only tested on Linux.

To install uv, you'll only need curl and a shell. Both are typically already installed on any Linux installation.

curl -LsSf https://astral.sh/uv/install.sh | sh

Preparation

First, attach the numato device via USB. Ensure you've got read/write access to the device. With dmesg you can find out which device file the board was made available by after attaching it, e.g. /dev/ttyACM0. With ls -l /dev/ttyACM0 you'll then be able to see which user and group the device file belongs to and see the permission. Usually the device will be owned by user root and group dialout. The common way of getting r/w permission for your user is, to join the dialout group like sudo adduser your_username dialout.

One-off execution of numato-gpio's numato-discover with uvx

To test whether your devices can be found, run the command-line interface like:

uvx --from numato-gpio numato-discover

Expected output:

❯ python3 -m numato_gpio
dev: /dev/ttyACM0 | id: 0 | ver: 00000009 | ports: 32 | iodir: 0xffffffff | iomask: 0x00000000 | state: 0x00000000
dev: /dev/ttyACM1 | id: 1 | ver: 00000009 | ports: 32 | iodir: 0xffffffff | iomask: 0x00000000 | state: 0x00000000

Usage API

The API can be used like:

import numato_gpio as gpio

# You can instantiate the device directly from its OS identifier, for instance
# "/dev/ttyACM0" on Linux or "COM5" on Windows.
dev = gpio.NumatoUsbGpio("/dev/ttyACM0")

# Alternatively, you can use the discovery function, but it is limited to
# Linux' /dev/ttyACM* devices. This is because discovery will open and try to
# interact with any device. This can lead to errors in unrelated devices.
# Under windows the naming scheme is entirely flat (COMx) increasing the error
# potential, so no discovery here.
# my_device_id = 0
# gpio.discover()
# dev = gpio.devices[my_device_id]

# Configure port 4 as output and set it to high
dev.setup(4, gpio.OUT)
dev.write(4, value=1)

# Configure port 27 as input and print its logic level
dev.setup(27, gpio.IN)
print(dev.read(27))

# Configure port 2 as input and print its ADC value
dev.setup(2, gpio.IN)
print(dev.adc_read(2))

# Configure port 14 as input and setup notification on logic level changes
dev.setup(14, gpio.IN)
def callback(port, level):
    print("{edge:7s} edge detected on port {port} "
        "-> new logic level is {level}".format(
        edge="Rising" if level else "Falling",
        port=port,
        level="high" if level else "low")
    )

dev.add_event_detect(14, callback, gpio.BOTH)
dev.notify = True

Release Versions

See changelog.

Troubleshooting

In case your device can't be discovered or you even get an error message or stacktrace, please follow the troubleshooting guide.

Known Issues

Though the code works well in a Home Assistant integration since 2018, there are quite some aspects to improve. The following issues are only the ones the author is aware of:

• Some docstrings are hard to understand
• Device discovery/registry as module-global dict is sub-optimal
• Only /dev/ACMx devices are scanned which were mapped on the author's Linux
• No async API available

Install development environment

If you plan to make a contribution use uv to set-up your development environment. Uv installs the dependencies and the numato-project (editable) in a virtualenv.

uv sync

You can now activate the virtualenv (.venv directory) like

source .venv/bin/activate

If you use VSCode or similar IDEs, ensure that their Python environment is configured to the .venv directory so their tools, like Debugger, Test Explorer etc., work.

Note that all commands of the Makefile are using uv run or uvx, so you don't have to activate the virtualenv before calling them.

System Tests

Unit tests in the tests directory are using a device mockup which mimics a Numato device's responses as far as known at the state of development.

System tests in the sys_tests folder are meant to be run using a real device and will just fail, if no device is connected. They are an important complement to unit tests, because they are the real thing and might behave differently than the mockup device for the unit tests.

If you consider to run system tests you should be aware that it may be dangerous running them.

WARNING

Only run the system tests with gpio ports disconnected! You otherwise risk a short circuit which may lead to damage or destruction of your device or worse.