@episensor/epi-gpio

A set of Node-RED nodes to interact with the GPIO on an EpiSensor Gateway.

Note: unlike the official Node-RED nodes, this does not include functionality for taking inputs from a keyboard or mouse.

Installation

You can install this node directly from the Node-RED Palette Manager or manually using npm:

npm install @episensor/epi-gpio

For EpiSensor Edge users: These GPIO nodes come pre-installed with your Edge device.

Usage

Note: the diagram in the configuration shows pin numbers - the BCM GPIO field allows you to enter the GPIO number directly (this allows you to use the node for other devices that have other BCM GPIO like the Pi Compute modules.)

Input node

Generates a msg.payload with either a 0 or 1 depending on the state of the input pin.

Outputs

msg.payload - number - the level of the pin (0 or 1)
msg.topic - string - pi/{the pin number}

You may also enable the input pullup resistor ↑ or the pulldown resistor ↓.

Output node

Can be used in Digital or PWM modes.

Input

msg.payload - number | string
Digital - 0, 1 - set pin low or high. (Can also accept boolean true/false)
PWM - 0 to 100 - level from 0 to 100%

Hint: The range node can be used to scale inputs to the correct values.

Digital mode expects a msg.payload with either a 0 or 1 (or true or false), and will set the selected physical pin high or low depending on the value passed in.

The initial value of the pin at deploy time can also be set to 0 or 1.

When using PWM mode, the input value should be a number 0 - 100, and can be floating point.

Development

Testing

This package includes a comprehensive testing framework to ensure compatibility with Node-RED. To run the tests:

npm test                # Run unit tests with Jest
npm run test:integration # Run integration tests
npm run test:node-red   # Test installation and loading in Node-RED
npm run security-check  # Run security checks
npm run verify-package  # Verify package can be installed and loaded
npm run pre-publish     # Run all tests before publishing

The testing approach is based on the one used in the edge-bacnet repository and includes:

Unit Tests: Tests for individual modules using Jest
Integration Tests: Tests that verify the nodes work together
Node-RED Compatibility: Tests that verify the nodes can be installed and loaded in Node-RED
Security Checks: Checks for vulnerabilities and outdated dependencies
Package Verification: Ensures the package can be correctly installed and used

Implementation Notes

Pure JavaScript Implementation: This package uses a native Node.js implementation for GPIO access with no external dependencies
The GPIO functionality is implemented using the sysfs interface on Linux
For testing on non-ARM architectures, the package will run in a simulated mode
Graceful fallback for environments without GPIO hardware

Cross-Platform Development

This package can be developed and tested on non-ARM platforms (like macOS or Windows):

On non-ARM architectures, the GPIO functionality is automatically disabled
All tests can be run on any platform, with appropriate simulations for GPIO hardware
The package gracefully handles the absence of GPIO hardware, making it easy to develop on any machine

Architecture

The package consists of the following main components:

gpio.js: A native Node.js implementation for GPIO access
epi-gpio.js: The main Node-RED node implementation
testgpio.js: A utility to test for GPIO availability

Credits

Node-RED
Dave Conway-Jones (ceejay@vnet.ibm.com)

Support

For more information, please visit EpiSensor Documentation or for support, visit EpiSensor Helpdesk

License

Apache 2.0