Having looked longingly at Sparkfun’s Tiny AVR programmer, I wanted the same functionality for my attiny USB stick. So I scrounged some old arduino stacking headers, and made another shield for it: Attiny25/45/85 programming shield!
The upper-landing attiny85 is programmable with the lower attiny85 (which acts as an usbtinyISP programmer, actually running LittleWire firmware). The stacking headers can be used right away for connecting the upper attiny to a breadboard via some jumper wires. In the photo above, I just tested the basic “blink”, using the small “breadboard” space on the lower landing.
If you want to make one yourself, this one is very easy: use a 4x6 piece of a protoboard, two 4x1 stacking headers and an 8-pin IC socket. Solder the socket in the middle of the protoboard, then stacking headers on the sides, and make connections from the headers to the adjacent IC socket pins. Finally, cut the middle two pins of the “left” stacking header: these pins are used for USB communication with the programmer attiny below and shouln’t be connected to the pins on the programee attiny above.
As the final touch, I taped little pieces of paper with pin names to the sides of the stacking headers, so that I won’t have to look up the attiny’s pinout every time I come back to it.
So, with this programming shield, with the ISP header shield I showed last time and with the LittleWire firmware, my stick is equivalent to Sparkfun’s Tiny AVR Programmer. (Of course, their stick is much nicer looking!)