little2wire

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!

l2w-top

Notice: I’m selling some of these on Tindie.

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:

l2w-bottom

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.

l2w-levtrans

BOM

Part Type Value Package Note
R1 Resistor array 68R 1206  
R2 Resistor array 1.5kR 1206  
C1 Capacitor 0.1uF 0805  
D1 Zener diode 3.6V SOD-323  
D2 Zener diode 3.6V SOD-323  
D3 LED amber 0805  
D4 LED green 0805  
IC1 ATtiny85   SOIC-8WIDE  
U1 male headers   2x3  
IC2 AMS1117 3.3V SOT-224 optional
C2 Capacitor 10uF 0805 optional w/IC2
C3 Capacitor 22uF 0805 optional w/IC2