Pi GPIO for Node-RED

2.0.7 · active · verified Sun Apr 19

The node-red-node-pi-gpio package provides a set of Node-RED nodes for interacting with the General Purpose Input/Output (GPIO) pins of a Raspberry Pi. Utilizing the `RPi.GPIO` Python library, it enables flow-based control and monitoring of digital and Pulse Width Modulation (PWM) outputs, as well as digital inputs. The current stable version is 2.0.7. Releases appear to follow a milestone-based cadence rather than a strict schedule, with major version updates incorporating new features or significant changes. Key differentiators include built-in support for mouse and keyboard input detection and direct integration into the Node-RED visual programming environment, simplifying hardware interaction for IoT and automation projects on Raspberry Pi devices. It specifically notes an alternative, `node-red-node-pi-gpiod`, for more accurate servo control, indicating this package is better suited for general purpose digital and basic PWM applications.

Common errors

```
Error: RPi.GPIO module not found
```
cause The Python `RPi.GPIO` library is not installed or not accessible to the user running Node-RED.

fix Install the Python `RPi.GPIO` library using `sudo pip install RPi.GPIO`. Ensure `python-pip` and `python-dev` are also installed (`sudo apt-get install python-pip python-dev`).
```
Permission denied to /dev/gpiomem (or similar GPIO access error)
```
cause The user running Node-RED lacks the necessary permissions to directly access the GPIO pins on the Raspberry Pi.

fix Add the Node-RED user (or the user running Node-RED) to the `gpio` group and ensure correct `udev` rules are in place. Run: `sudo addgroup gpio`, `sudo chown root:gpio /dev/gpiomem`, `sudo adduser $USER gpio`, `echo 'KERNEL=="gpiomem", NAME="%k", GROUP="gpio", MODE="0660"' | sudo tee /etc/udev/rules.d/45-gpio.rules`, then `sudo udevadm control --reload-rules && sudo udevadm trigger`. Replace `$USER` with the actual user Node-RED runs as.
```
PWM output is erratic or inaccurate, especially with servos.
```
cause The `node-red-node-pi-gpio` package uses software-driven PWM which can be affected by system load and scheduling, leading to timing jitters.

fix For applications requiring high precision PWM (like servo control), switch to `node-red-node-pi-gpiod`. This package uses the `pigpiod` daemon for hardware-timed PWM, offering significantly better accuracy.

Warnings

breaking This package relies on the `RPi.GPIO` Python library and specific system permissions. On non-Raspbian operating systems (e.g., Ubuntu, Debian on a Pi), you *must* manually install `python-pip`, `python-dev`, the `RPi.GPIO` Python package, configure `udev` rules, and add your user to the `gpio` group. Failure to do so will result in GPIO access errors.
Fix: Execute the following commands: `sudo apt-get install python-pip python-dev`, `sudo pip install RPi.GPIO`, `sudo addgroup gpio`, `sudo chown root:gpio /dev/gpiomem`, `sudo adduser $USER gpio`, `echo 'KERNEL=="gpiomem", NAME="%k", GROUP="gpio", MODE="0660"' | sudo tee /etc/udev/rules.d/45-gpio.rules`, `sudo udevadm control --reload-rules && sudo udevadm trigger`.
gotcha For applications requiring highly accurate or fine-grained servo control, this package's PWM mode may not be sufficient. The underlying `RPi.GPIO` library can have timing inaccuracies for demanding PWM tasks.
Fix: Consider using the `node-red-node-pi-gpiod` package instead, which leverages the `pigpiod` daemon for more precise hardware-timed PWM control suitable for servos.
gotcha When configuring GPIO pins, ensure you are using the correct BCM GPIO number, not the physical pin number. The Node-RED configuration diagram shows pin numbers for reference, but the input field expects the Broadcom (BCM) GPIO numbering scheme.
Fix: Always cross-reference the BCM GPIO numbering for your Raspberry Pi model (e.g., using online pinout diagrams) to ensure you are configuring the intended physical pin.
gotcha The `rpi gpio out` node expects different `msg.payload` types depending on whether it's configured for Digital or PWM mode. Sending the wrong type or range can lead to unexpected behavior.
Fix: For Digital mode, `msg.payload` should be `0`, `1`, `true`, or `false`. For PWM mode, `msg.payload` must be a number between `0` and `100` (representing percentage duty cycle). Use a Node-RED `range` node to scale inputs if necessary.

Install

npm install node-red-node-pi-gpio npm
yarn add node-red-node-pi-gpio yarn
pnpm add node-red-node-pi-gpio pnpm

Imports

Pi GPIO Input Node
```
Install via Node-RED palette manager or `npm i node-red-node-pi-gpio`
```
This package provides nodes for Node-RED, not JavaScript symbols for direct `import` statements. Nodes are added to the Node-RED palette upon successful npm installation into the Node-RED user directory.
Pi GPIO Output Node
```
Install via Node-RED palette manager or `npm i node-red-node-pi-gpio`
```
These nodes are accessed visually within the Node-RED flow editor after installation, appearing in the palette under the 'rpi gpio' category.
Pi GPIO Keyboard/Mouse Node
```
Install via Node-RED palette manager or `npm i node-red-node-pi-gpio`
```
This node detects keyboard clicks and mouse button events directly from the hardware, bypassing application focus. Functionality may vary across different OS setups (YMMV).

Quickstart

Describes the installation process and guides a user through creating a basic Node-RED flow with Pi GPIO Input, Output, and Debug/Inject nodes.

/*
  This quickstart demonstrates how to install 'node-red-node-pi-gpio' and describes a basic Node-RED flow setup.
  Since this is a Node-RED node package, direct JavaScript runtime usage is not applicable.
  The instructions guide you through setting up a simple input-to-debug and inject-to-output flow in the Node-RED editor.
*/

// Step 1: Install the Node-RED node package.
// You should run this command in your Node-RED user directory (typically ~/.node-red)
// or use the 'Manage Palette' option within the Node-RED editor.
console.log("Executing installation command:\n  npm i node-red-node-pi-gpio\n");

// After installation, restart Node-RED if prompted or if nodes do not appear in the palette.
console.log("Installation complete. If nodes are not visible, restart Node-RED (e.g., 'node-red-start').\n");

// Step 2: Configure a basic flow in the Node-RED editor (usually accessible at http://localhost:1880).
console.log("--- Node-RED Flow Configuration Guide ---");
console.log("1. Drag an 'rpi gpio in' node from the palette onto your flow canvas.");
console.log("   - Double-click the 'rpi gpio in' node: Select a BCM GPIO number (e.g., 4) and configure pull-up/down resistors if needed.");
console.log("2. Drag a 'debug' node onto the canvas.");
console.log("   - Connect the output of the 'rpi gpio in' node to the input of the 'debug' node.");
console.log("   - When the state of GPIO 4 changes, you will see '0' or '1' in the debug sidebar.");
console.log("3. Drag an 'inject' node onto the canvas.");
console.log("   - Double-click the 'inject' node: Set 'Payload' to a number (e.g., 1 for digital high, or 50 for 50% PWM).");
console.log("4. Drag an 'rpi gpio out' node onto the canvas.");
console.log("   - Double-click the 'rpi gpio out' node: Select a BCM GPIO number (e.g., 17) and choose 'Digital output' or 'PWM output' mode.");
console.log("5. Connect the output of the 'inject' node to the input of the 'rpi gpio out' node.");
console.log("   - Clicking the 'inject' node's button will now set the state of GPIO 17.");
console.log("6. Click the 'Deploy' button in the Node-RED editor to activate your flow.");

// Note: On non-Raspbian systems, additional Python library and Udev rules setup is required. (Refer to warnings for details).

view raw JSON →