little2wire

Little²wire is my take on the classic Little Wire USB stick: surface mounted parts, as small and flat as possible, with an option for 3.3V operation, and optionally a micro or mini USB connector. Still solderable by hand!

Notice: I'm no longer selling these on Tindie. If you really want one, please get in touch - I may have some spare PCBs and parts.

The idea is not new in any way - the basic schematic + VUSB library, popularised by Little Wire, has been adopted by some successful projects: DigiSpark, Adafruit Trinket, as well as some perhaps less well-known ones like picoDuino and USBasp-t.

The design of this board is directly inspired by the latter two. The differences are:

• USB connector directly on the PCB, with the micro and mini USB sockets option.
• An option for 3.3V operation (in which case the bottom side of the PCB needs to be populated and the zener diodes can be omitted).
• Standard AVR ISP header, like Little Wire. This can be used initially for programming the attiny85 (with the micronucleus bootloader) and after disabling RESET via fuses, it functions as a normal ISP header with attiny85 acting as a programmer.
• A solder jumper to select between 3.3V and 5V.
• Selecting whether to supply power to the ISP header is done also via a solder jumper.

The board in between the two little²wires below is my AVR ISP level translator, based on GTL2003 chip, with 3V3 regulator and designed to be as flat as possible.

Links

• Little²wire EAGLE files
• Little²wire PCB on OSH Park

BOM