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dxGpio

1. Overview​

This module is part of the official dejaOS system module library. It provides GPIO output control.

What it does: A GPIO pin can only be driven to high level (1) or low level (0). Typical use cases include driving relays (door lock / electric strike), indicator outputs, and other on/off hardware. When a relay is wired to the pin, high usually means energized (door open) and low means de-energized (door closed) — confirm against your hardware schematic.

How it differs from dxGpioKey: dxGpio is for output (your app controls the pin). dxGpioKey is for input (external digital inputs report state changes). They are often used together: input events reflect peripheral state, output drives relays and other actuators.

Features:

  • Initialize and release GPIO resources
  • Request / free individual GPIO pins
  • Set and read output level (0 / 1)
  • Configure pin function, pull state, and drive strength (device-specific)

2. Files​

  • dxGpio.js
  • libvbar-b-dxgpio.so

Ensure these files are placed under the dxmodules subdirectory in your project root.

3. Dependencies​

  • None

4. Compatible Devices​

Compatible with dejaOS v2.0+ devices that expose controllable GPIO pins. GPIO pin numbers and function codes are device-specific — use constants from dxDriver (e.g. dxDriver.GPIO.RELAY0) rather than hard-coding values.

5. Usage​

Basic usage​

import gpio from "./dxmodules/dxGpio.js";
import dxDriver from "./dxmodules/dxDriver.js";

// Initialize once
gpio.init();

// Request relay pin and configure as output (request() also sets function 0x04)
gpio.request(dxDriver.GPIO.RELAY0);

// Energize relay (door open)
gpio.setValue(dxDriver.GPIO.RELAY0, 1);

// De-energize relay (door closed)
gpio.setValue(dxDriver.GPIO.RELAY0, 0);

// Read current output level
let level = gpio.getValue(dxDriver.GPIO.RELAY0);

// Release when done (optional)
gpio.free(dxDriver.GPIO.RELAY0);
gpio.deinit();

Timed pulse output​

A common relay pattern is to drive the pin high, then return to low after a delay:

import gpio from "./dxmodules/dxGpio.js";
import dxDriver from "./dxmodules/dxDriver.js";
import std from "./dxmodules/dxStd.js";

const relayPin = dxDriver.GPIO.RELAY0;
const holdMs = 3000;

gpio.init();
gpio.request(relayPin);

gpio.setValue(relayPin, 1);
std.setTimeout(() => {
  gpio.setValue(relayPin, 0);
}, holdMs);

6. API Reference​

gpio.init()​

Initialize the GPIO subsystem. Call once before other operations.

Returns: boolean — true on success

gpio.deinit()​

Release GPIO resources.

Returns: boolean

gpio.request(gpio_)​

Request a GPIO pin and configure it for output (internally calls setFunc(gpio_, 0x04)).

Parameters:

  • gpio_ (number): GPIO identifier for the device, required

Returns: boolean

gpio.free(gpio_)​

Release a previously requested GPIO pin.

Parameters:

  • gpio_ (number): GPIO identifier, required

Returns: boolean

gpio.setValue(gpio_, value)​

Set output level.

Parameters:

  • gpio_ (number): GPIO identifier, required
  • value (number): 1 = high, 0 = low, required

Returns: boolean

gpio.getValue(gpio_)​

Read current output level.

Parameters:

  • gpio_ (number): GPIO identifier, required

Returns: number — 1 or 0

gpio.requestGpio(gpio_)​

Request a GPIO pin only (does not set function). Use with setFuncGpio when you need custom pin configuration.

Returns: boolean

gpio.setFuncGpio(gpio_, func)​

Set GPIO function attribute (device-specific, see dxDriver.GPIO_FUNC).

Returns: boolean

gpio.setPullState(gpio_, state) / gpio.getPullState(gpio_)​

Configure or read pull-up / pull-down state.

gpio.setDriveStrength(gpio_, strength) / gpio.getDriveStrength(gpio_)​

Configure or read drive strength.

7. Constants​

GPIO function values are defined per device in dxDriver.GPIO_FUNC, for example:

dxDriver.GPIO_FUNC = {
  GPIO_FUNC_3:  0x03,
  GPIO_OUTPUT0: 0x04, // output, default low
  GPIO_OUTPUT1: 0x05, // output, default high
};

Relay pin numbers are defined in dxDriver.GPIO, for example on VF203:

dxDriver.GPIO = {
  RELAY0: 44,
  RELAY1: 84,
};
  • dxGpioKey: GPIO input monitoring (door sensor, fire alarm, tamper, etc.)
  • dxDriver: Device-specific GPIO / relay pin constants

9. Examples​

None.