pyhid-usb-relay 0.1.0

A tool for controlling USB HID relays

Python Utility for controlling HID USB Relays

This utility is a Python version of usb-relay-hid

Getting Started

Setup a python virtual environment and install requirements:

python3 -m venv venv
. venv/bin/activate
pip install -r requirements.txt

The module can be installed with:

./setup.py install

The provided pyhid-usb-relay command is pretty much the same as the hidusb-relay-cmd from the usb-relay-hid project, and aims to be feature compatible. Additional commands are implemented, and the best way to discover what options are available is to run:

pyhid-usb-relay --help

Configuration

Coming soon

Permissions

If you want to access the relay devices as a normal user (which is recommended, since it will respect your local configuration), you will need to modify your udev rules to allow access to the HID device. You can do this by creating a file named /etc/udev/rules.d/90-hidusb-relay.rules with the following contents:

# Give all users access to USB HID Relay
SUBSYSTEM=="usb", ATTRS{idVendor}=="16c0", ATTRS{idProduct}=="05df", MODE:="0660", GROUP="dialout"

You may need to reload your udev rules with sudo udevadm control --reload-rules and unplug and reattach the USB relay board for this to take effect

NOTE This rule allows any user that is part of the dialout group to access the board. If this is not what you want, you should change the udev rules.

Fixing Serial Numbers

The relays that this tool is designed to control have a quirk that they all report the same USB Vendor, Product, and Serial Number (The serial number used by this code is retrieved by the HID API). This can make it hard to distinguish between multiple relays attached to the same device using udev rules.

The pyhid-usb-relay tool can be used to help resolve this by using the get-serial subcommand, which will fetch the HID serial number from the device with a udev rule that looks like:

SUBSYSTEM=="usb", ATTR{idVendor}=="16c0", ATTR{idProduct}=="05df", ACTION=="add", PROGRAM="/usr/local/bin/pyhid-usb-relay get-serial '%E{BUSNUM}' '%E{DEVNUM}'", ENV{ID_SERIAL}:="%c"