bicolor-bargraph

Johnny-Five component for an Adafruit Bi-Color 24 Bargraph

Install

$ npm i johnny-five bicolor-bargraph

Requirements

• Node.js v6.x or newer

Example

The following naive example shows how a CPU load indicator (updating every second) can be created for a Raspberry Pi.

• When the load is light, a handful of green LEDs will display
• When the load is moderate, these green LEDs will display, as well as yellow ones
• When the load is heavy, you get green + yellow + red

The bar graph has 24 bars; thusly the colored sections are each of size 8.

'use strict';

const percent = require('cpu-percent');
const j5 = require('johnny-five');
const raspi = require('raspi-io');
const bargraph = require('bicolor-bargraph');

function color(i) {
  if (i > 16) {
    return bargraph.GREEN;
  } else if (i > 8) {
    return bargraph.YELLOW;
  }
  return bargraph.RED;
}

new j5.Board({
  io: new raspi(),
  repl: false
}).on('ready', () => {
  const bar = bargraph();
  percent((err, value) => {
    if (err) {
      throw err;
    }
    // invert numbers to change "direction"
    const pct = Math.round(24 * (100 - value) / 100);
    const [cols, values] = [[], []];
    for (let i = 0; i < 24; i++) {
      cols.push(i); 
      values.push(pct <= i ? color(i) : bargraph.OFF);
    }
    // sets many LEDs at once in a single I2C write
    bar.leds(cols, values);
  });
});

I'm Calling This "Usage"

Other methods are available, similarly to the Led.Matrix component:

• on(): enable component (happens automatically upon instantiation)
• off(): disable component
• clear(): turn all LEDs off
• brightness(value): 0-100
• blink(value): blink at 2 HZ, (0x02), 1 HZ (0x04), or 0.5 HZ (0x06). Default is no blinking (0x00)
• led(bar, value): Control an individual bar, where value is a color (see constants below)

The module exports class BicolorBargraph if you want it, but its default export is a factory function.

It exports constants RED, GREEN, YELLOW, and OFF to help with the colors.

It should support multiple devices, but I don't have multiple devices to test.

The module supports some options via the factory function or constructor, but probably best to leave them be.

Prior Art

This module is based on:

• Adafruit_Python_LED_Backpack
• johnny-five

License

Copyright 2017 Christopher Hiller. Licensed Apache-2.0