leddriver

a node.js library to control a SPI led driver (p.e adafruit leddriver) with your Raspberry Pi

node-leddriver

This is a node.js library to control a SPI led driver.

I wrote this to control my Adafruit 24-Channel 12-bit PWM LED Driver using the TLC5947 with my Raspberry Pi. This should also work with different SPI devices or host systems but my examples referr to this configuration. It could also be used for other PWM modules like motor controls etc.

npm install leddriver
var LEDDRIVER = require("leddriver");
var driver = new LEDDRIVER(24, 12);

parameters:

  • the number of channels your leddriver has
  • the bits per channel of your leddriver
  • (optional) the name of the SPI device (if omitted /dev/spidev0.0 as defined in node-simplespi )
driver.set(5, 819);

parameters:

  • the channelnumber to set (0 to number of channels - 1)
  • the direct value to set in the channel

This example sets the value of channel 5 to 500. The maximum allowed value depends on the bits per channel of your device. Since I am using a 12bit SPI device it has 3 hexadecimal digits per channel ("000" to "FFF"). In decimal this is a value between 0 and 4095.

driver.pset(5, 0.2);
  • the channelnumber to set (0 to number of channels - 1)
  • the percentage to set in the channel (0 - 1)

This example sets the value of channel 5 to 0.2 * maximum value. In my 12bit example this has exactly the same result like the first example (0.2 * 4095 = 819) but it is far easier to use like this.

driver.send();

This updates your led driver by sending the values.

var LEDDRIVER = require("leddriver");
var driver = new LEDDRIVER(24, 12);
 
driver.pset(0, 1);
driver.pset(1, 0);
driver.pset(2, 1);
driver.send();
 
setTimeout(function() {
 
    driver.pset(0, 0.5);
    driver.pset(1, 0.5);
    driver.pset(2, 0.5);
    driver.send();
 
}, 5000);

When running this example the LEDs connected to channel 0 and 2 should be fully turned on while channel 1 is off. After 5 seconds all the LEDs go to half brightness.

The library also includes a helper for setting RGB-LEDs to a color defined in csslike hex style:

driver.setRGB("#e010ff", 0, 1, 2);

parameters:

  • the color to set as hexcode
  • the channel of the red LED
  • the channel of the green LED
  • the channel of the blue LED
  • (optional) the channel of the second blue LED

When driving with MOSFETS like discussed in the adafruit Forums you should invert (1=0, 0=1) your output. You can turn on inversion of setRGB:

driver.invert();

thx @ jnovack

Connect your Pi like this to the LED driver:

Raspberry Piled driver
GNDGND
5V or 3.3V (or external)input V+
SCLKinput CLK
MOSIinput DIN
CE0input LAT

Connect /OE on the LED driver to GND or to a GPIO of your choice (you can quickly turn off all LEDs by using a GPIO).

The SPI interface requires root access on the Raspberry Pi. Run your app with sudo! For more details on getting SPI to run see node-simplespi!

I am not responsible for any damages to your hardware. Use this at your own risk.