The PiGlow is a small add on board for the Raspberry Pi that provides 18 individually controllable LEDs. You can use it for all sorts of things! And of course, it fits inside a Pibow!

Works just fine with all models of Raspberry Pi including the B+!

There are tons of things you can do with it:

Mood lighting / ambience
Showing current system load
Notify you of events like mentions in tweets or incoming e-mail
Feedback the status of scripts/daemons running on your Pi
Works great when VESA mounted to provide a cast against a wall
...and pretty much anything else you can think of!

PiGlow sample code and other instructions

If you just want some Python code to start tinkering with please check out our GitHub repository which also includes the full datasheet for the IC used on PiGlow.

Gordon Henderson has added a PiGlow driver for wiringPi which you can find here: http://wiringpi.com/dev-lib/piglow/

Simon Walters has added PiGlow support for Scratch which is here: http://cymplecy.wordpress.com/

Jason Barnett has put together a great Python class and a load of samples: https://github.com/Boeeerb/PiGlow

Ben Lebherz has forked Jasons project and tidied up the code a bit while adding gamma correction: https://github.com/benleb/PyGlow

Manuel Ernst has created a Node.js library: https://github.com/zaphod1984/node-piglow

Falldeaf has put together a nice XBMC hack to use the PiGlow as a status indicator: http://falldeaf.com/2013/11/the-xbmc-piglow-information-display-addon/

Jonathan Stowe has created a module for the Perl divers among you: https://metacpan.org/release/JSTOWE/Device-PiGlow-1.0

Toon Schoenmakers has gone as far as making a library for Golang: https://github.com/schoentoon/piglow

More detail

This board uses the SN3218 8-bit 18-channel PWM chip to drive 18 surface mount LEDs. Communication is done via I2C over the GPIO header with a bus address of 0x54 (Python example code provided). Each LED can be set to a PWM value of between 0 and 255.