Servo

Library for controlling servos

Install command

curl -o src/libs/servo.ts https://c2coder.github.io/Jaculus-libraries/data/servo/servo.ts

Basic usage

import { Servo } from "./libs/servo.js"

const SERVO_PIN = 35;
const TIMER = 1;
const CHANNEL = 3;
const servo = new Servo(SERVO_PIN, TIMER, CHANNEL);

servo.write(0);    // 0°
servo.write(512);  // 90°
servo.write(1023); // 180°

Multiple servos

import { Servo } from "./libs/servo.js"

const SERVO_PIN = 35;
const TIMER = 1;
const CHANNEL_1 = 3;
const CHANNEL_2 = 4;

const servo_1 = new Servo(SERVO_PIN, TIMER, CHANNEL_1);
const servo_2 = new Servo(SERVO_PIN, TIMER, CHANNEL_2);

servo_1.write(0);    // 0°
servo_2.write(0);    // 0°

servo_1.write(512);  // 90°
servo_2.write(512);  // 90°

servo_1.write(1023); // 180°
servo_2.write(1023); // 180°

Source code:

import * as ledc from "ledc";

/**
 * A class for controlling a servo motor.
 */
export class Servo {
	private channel: number; // the PWM channel to use

	/**
	 * Create a new servo object.
	 * @param pin The pin the servo is connected to.
	 * @param timer The timer to use for PWM.
	 * @param channel The channel to use for PWM.
	 */
	constructor(pin: number, timer: number, channel: number) {
		this.channel = channel;
		ledc.configureTimer(timer, 50, 12); // 50Hz is the frequency of a servo, 12 is the resolution of the timer
		ledc.configureChannel(channel, pin, timer, 1023); // 1023 is the resolution of a servo
	}

	/**
	 * Set the servo position.
	 * @param value The position to set the servo to, from 0-1023.
	 */
	write(value: number) {
		// map the value from 0-1023 to 0.5-2.5ms
		const ms = ((value / 1023) * 2) + 0.5; // 0.5-2.5ms is the range of a servo

		// convert to a duty cycle
		const duty = (ms / 20) * 1023;  // 20ms is the period of a servo

		ledc.setDuty(this.channel, duty); // set the duty cycle to the servo
	}
}