leddriver

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.

installation

npm install leddriver

initialization

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 )

directly setting values

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.

percentage value setting

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.

sending the values to your driver

driver.send();

This updates your led driver by sending the values.

example

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.

setting RGB-LEDs

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

Special issues with MOSFETS

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

wiring the Raspberry Pi (example with adafruit led driver)

Connect your Pi like this to the LED driver:

Raspberry Pi	led driver
GND	GND
5V or 3.3V (or external)	input V+
SCLK	input CLK
MOSI	input DIN
CE0	input 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.