Since its inception, I’ve been a big fan of Digispark — the minuscule development board from Digistump (http://digistump.com). I’ve already prototyped a couple of designs based on Digispark, turning all of them into useful little gizmos for home/hobby applications.
Little Wire & Digispark
Recently, I found some information about the Little Wire for Digispark Shield Kit, which allows the Digispark to be easily used as a Little Wire device with the Little Wire firmware and libraries. Little Wire is a multi-featured, USB-controlled, open-source hardware tool packed in a minimal form factor (designed by Ihsan Kehribar). I’m glad that Digistump started selling shield kits to use Digispark with the Little Wire firmware more conveniently.
Little Wire for Digispark Shield Kit
The Little Wire for Digispark Shield Kit (designed for use with the Digispark development board) is an unassembled kit that demands basic soldering skills. After successful construction, you can load the requisite firmware as follows:
• Download the Little Wire firmware installer for your OS platform at http://littlewire.cc/downloads.html (under “Single click installers for v1.3 firmware”)
• Run the execution, and when prompted, plug in the Digispark that you will be using with the finished shield kit. Watch the command window to proceed (see screenshots given below).
Thereafter, Digispark becomes a Little Wire device about five seconds after it’s plugged into your computer.
For my Windows 7 (x64) PC, I downloaded the needed Windows Driver (64 bit) located under the “Binaries” section of the downloads page (http://littlewire.cc/downloads.html).
Note that the Little Wire firmware does not replace the Digispark software because it is a program uploaded in the same way as an Arduino sketch. So you can replace it again with an Arduino sketch via the usual upload process.
If the Little Wire shield kit is not within your easy reach, you can still construct your own shield with the help of a small perforated circuit board or Digispark protoboard. As the original shield provides jumper-enabled pull-ups for the I2C lines (plus an external VCC jumper), that option is also included in the schematic presented here. Furthermore, if you think that it would be great to wire up the Digispark protoboard with a DIP-8 socket to program your Attiny85s, it’s possible to do so without too much difficulty. Just solder the IC socker and link six wires from it to the AVR ISP header in the right order. That’s it!
For the curious, here is the pin assignment of Attiny85. Keep an eye on the four connections: MOSI, MISO, SCK, and RESET (don’t forget that you need to wire up VCC and GND for the IC socket).