dxPwm

1. Overview

This module is part of the official system module library of dejaOS, used for PWM (Pulse Width Modulation) control functionality. It includes comprehensive PWM control features:

• PWM channel initialization and management
• Power level control (0-100 range)
• Beep sound generation with customizable parameters
• Pre-defined beep patterns for different scenarios (press, success, fail, warning)
• Cross-thread PWM control support

On some devices, the PWM output is connected to an LED instead of a buzzer: in this case, setPower controls LED brightness (duty cycle), and pwm.beep() becomes a blink pattern (with volume interpreted as blink brightness). Channel indexes must match your hardware design. If no channel is passed, most APIs default to channel 0.

2. Files

• dxPwm.js
• libvbar-b-dxpwm.so

• Ensure these 2 files are included in the dxmodules subdirectory under your project root directory

3. Dependencies

• None

4. Compatible Devices

Compatible with all devices running dejaOS v2.0+ that have PWM hardware support.

5. Usage

Basic Usage

import pwm from '../dxmodules/dxPwm_new.js'
import logger from '../dxmodules/dxLogger.js'
import std from '../dxmodules/dxStd.js'
import * as os from "os"

// Initialize PWM channel
pwm.init(); // channel 0

// Set power level
let power = 0
pwm.setPower(power)
os.sleep(500)

power = 50
pwm.setPower(power)
os.sleep(300)

power = 0
pwm.setPower(power)
os.sleep(500)

// Generate a simple beep
pwm.beep({
    delay: 50,
    interval: 50,
    count: 2
})

// Use pre-defined beep patterns
pwm.pressBeep();    // Short beep for key press
pwm.successBeep();  // Two short beeps for success
pwm.failBeep();     // Long beep for failure
pwm.warningBeep();  // Standard warning beep

PWM for LED (Brightness and Blinking)

The example below assumes channel 0 drives a white LED and channel 1 is another output (for example, NIR). Only the white channel is used in this demo. For multi-channel use, initialize each channel before use.

import pwm from "../dxmodules/dxPwm_new.js";
import logger from "../dxmodules/dxLogger.js";
import * as os from "os";

// Channel IDs must match hardware wiring.
// If channel is omitted, init / setPower / beep usually use channel 0 by default.
const CHANNEL_WHITE = 0;
const CHANNEL_NIR = 1; // Not used in this demo

// Initialize the PWM channel before any operation on it.
let resp = pwm.init(CHANNEL_WHITE);
logger.info("PWM init: " + resp);

// --- Steady light: setPower(0-100) controls duty cycle / brightness ---
let power = 0;
pwm.setPower(power, CHANNEL_WHITE);
os.sleep(500);

power = 10; // Example low brightness; tune per hardware and visual effect
pwm.setPower(power, CHANNEL_WHITE);
os.sleep(2000);

power = 0;
pwm.setPower(power, CHANNEL_WHITE);
os.sleep(500);

// --- Blink pattern: beep is "sound" on a buzzer, but "blink rhythm" on LED ---
// time: LED on duration per blink (ms)
// interval: pause between blinks (ms)
// count: number of blinks
// volume: brightness level during blink (0-100)
logger.info("Two short blinks demo");
pwm.beep(
  {
    time: 50,
    interval: 50,
    count: 2,
    volume: 80,
  },
  CHANNEL_WHITE
);

6. API Reference

pwm.init(channel)

Initializes the specified PWM channel. Must be called before any other PWM operations on that channel.

Parameters:

• channel (number): The PWM channel number to initialize, default 0

Returns: object - Initialization result object

Note: This function must be called before using any other PWM functions on the specified channel.

pwm.deinit(channel)

Releases and cleans up the designated PWM channel.

Parameters:

• channel (number): The PWM channel number to deinitialize, default 0

Returns: boolean - true if deinitialization successful, false otherwise

Throws: Error if channel parameter is invalid

pwm.setPower(power, channel)

Sets the power level of the specified PWM channel.

Parameters:

• power (number): Power level (0-100), required
• channel (number): The PWM channel number to use, default 0

Returns: boolean - true if power set successfully, false otherwise

Throws: Error if power or channel parameters are invalid

Power Range:

• 0: No power output
• 1-99: Variable power levels
• 100: Maximum power output

pwm.beep(options, channel)

Generates a beep sound with customizable parameters.

Parameters:

• options (object): Beep configuration parameters, optional
  • count (number): Number of beeps, default 1
  • time (number): Duration of each beep in milliseconds, default 50
  • interval (number): Interval between beeps in milliseconds, default 50
  • volume (number): Beep volume (0-100), default 50
• channel (number): The PWM channel to use, default 0

Returns: void

Note: This function returns immediately and performs beeping in the background. The PWM channel must be initialized with pwm.init() before using this function.

Example:

// Custom beep pattern
pwm.beep({
    count: 3,      // 3 beeps
    time: 200,     // Each beep lasts 200ms
    interval: 100, // 100ms pause between beeps
    volume: 80     // 80% volume
}, 0);

pwm.pressBeep(volume, channel)

Plays a short beep, typically used for key press feedback.

Parameters:

• volume (number): Beep volume (0-100), default 50
• channel (number): The PWM channel to use, default 0

Returns: void

Configuration: Single beep, 30ms duration

pwm.successBeep(volume, channel)

Plays two short beeps, typically used to indicate successful operations.

Parameters:

• volume (number): Beep volume (0-100), default 50
• channel (number): The PWM channel to use, default 0

Returns: void

Configuration: Two beeps, 30ms duration each

pwm.failBeep(volume, channel)

Plays a long beep, typically used to indicate failure or error conditions.

Parameters:

• volume (number): Beep volume (0-100), default 50
• channel (number): The PWM channel to use, default 0

Returns: void

Configuration: Single beep, 500ms duration

pwm.warningBeep(volume, channel)

Plays a standard beep, typically used as a warning signal.

Parameters:

• volume (number): Beep volume (0-100), default 50
• channel (number): The PWM channel to use, default 0

Returns: void

Configuration: Single beep, 50ms duration

7. Constants

No specific constants are defined in this module. However, the following ranges are used:

• Channel Range: 0 and up (device-dependent)
• Power Range: 0-100 (0 = no power, 100 = maximum power)
• Volume Range: 0-100 (0 = no sound, 100 = maximum volume)

8. Related Modules

9. Example

None.