I love V-USB … bought my VID/PID a couple of years ago for my own little toys and playing around in my home lab. With the release of the Digispark and the Trinket (t85 based), a renewed interest seems to be brewing. So, I thought I would share a few of my homemade enablers - that is, things to help with prototyping… and things that can be reused with the next project idea.
The designs I present here work with 3.3V devices and 5.0V devices; however please refer to the Objective Development’s reference designs for ideas and specific values of things such as resistors and zener diodes. Listed below are my reference parts that I selected because they are known to work for me - the most critical is the zener diode. The 1.8K pullup can vary in specs based upon the reference design and source voltage.
- Zener 3.6V - 1N5227B-TAP by Vishay Semi (sourced: Newark 18M3528)
- 68 Ohm 1W metal film resistor 5% (sourced: Newark 78R4762)
- 1.8K Ohm 125MW 1% metal film resistor (sourced: Newark 38K5432)
PLEASE DO NOT POST ASKING ABOUT PARTS VALUES OR SUBSTITUTES. I SPENT A LONG TIME FINDING PARTS THAT WORK CONSISTENTLY FOR ME. YOUR MILEAGE MAY VARY.
For Arduino UNO/Mini/Nano boards AND for 328P-PU bareboards and breadboarding, I use this library:
For Trinket and Digispark both of which are t85-based, they both provide V-USB enabled bootloaders and user libraries for HID.
Other Adafruit software: GitHub - adafruit/Adafruit-Trinket-USB: Arduino libraries allowing Trinket to act as USB devices
Other Digispark software: Digistump LLC · GitHub
Now for the picture review of my hardware implementations for enabling a good prototyping experience. The traditional method of just sticking the parts into the breadboard is the 1st picture shown. By moving the V-USB interface parts to a small, epoxy encapsulated board, only V+, Gnd, D+, and D- (Red, Black, Yellow, Green) need to be connected to almost any Arduino to provide the V-USB interface. In my designs, I also use a small polyfuse just to protect my PC USB port.
For non-members and those not logged in, Flickr hosted versions;
Nano with V-USB adapter: http://www.flickr.com/photos/77727388@N06/10439987003/
V-USB adapters complete with polyfuse: http://www.flickr.com/photos/77727388@N06/10439987723/