We only need one pull-up on each line, so I can reuse the board from Week 5 as a second node in the network. The only real change on this board is that I added 10K pull-up resistors on SCL and SDA. Week 5, since we already have SCL (the clock line), SDA (the data line), and power and ground available to other boards on the 2x3 ISP header. I made a new board with the ATTiny44-basically the same as the one from

I decided to work with I2C this week since it's useful.

The Introducing Trinket documentation says that NeoPixels will work with either the 3V or 5V version at clock speeds of either 8MHz or 16MHz, but I've only tested it on 5 volt, 16MHz MCUs.Week Eleven: Networking and Communications It was a nice way to quickly test code and timing issues. My first prototype was tested using an Adafruit Trinket 5V, by the way. The circuit employs a voltage regulator and been used successfully between ambient temperatures of 25F and 100F without NeoPixel issues. If I remember correctly, the internal clock is an RC circuit that could therefore be affected by temperature and power supply fluctuation. It was not tested with a 3.3 volt supply, however. I've tested the scheme on the bench with multiple NeoPixels, as well. Not shown in the schematic are 10uF and 0.1uF noise-reduction capacitors placed across +5v and ground near the NeoPixel. Here's a partial schematic and a photo of the final PCB showing how a single NeoPixel was connected to the ATtiny85. I've done it successfully with the internal 16MHz clock on an ATtiny85 that was powered by 5 volts, programmed with the Arduino IDE and the Adafruit NeoPixel library.

Attiny88 wire library