Datasheet

Design

The Pixie was designed by Ytai Ben-Tsvi, who joins us below with "how he did it"

Don't forget to read the whole thing for a bonus photo at the end!

Take it away, Ytai!

Overview

While having a fairly simple functionality, the Pixie design has more than meet the eye. In

contrast to its low-power relatives, the NeoPixels, switching current to a chain of 3W LEDs

creates some interesting engineering challenges, which took a few iterations to get right.

Here’s what we’ve learned and how we’ve approached some of the interesting problems.

Microcontroller

Fairly early down the design path, it became clear that implementing all the features we

wanted is a task most suited for a small microcontroller. We chose the 8-bit Microchip

PIC12F1571, which had just about everything we could hope for in this application. It is

small and cheap, works on 5V, has exactly 5 I/O pins (used for R, G, B, Din, Dout), an

internal oscillator, a 16-bit, 3 channel PWM module, on-die temperature sensor and more.

Pretty amazing!

Programming the PIC12 is done through exposed pads featured on the circuit for that

purpose (labeled rst/pgd/pgc). A cheap PIC programmer can be used, but the programming

protocol is so simple that we’ve implemented an Arduino library that can do that for our

testbed.

The possibilities with having an on-board microcontroller are endless! The Pixie can be

reprogrammed for standalone operation, and the Din/Dout pins can be repurposed to

support different protocols or to directly connect to buttons, etc. The Dout pin can even be

used for analog input!

The exiting firmware can be found in Pixie's Github repository. (http://adafru.it/iNF)