I always like a challenge, so when I saw [simpleavr]s vusbtiny programmer, I started to wonder how small I could make an AVR programmer. All in all I’m pretty pleased with the result.
The schematic is almost the same as the original one. I’ve only added a LED and a resistor to indicate a proper power supply.
Since I wanted to try a simple USB connector made only with some bare pads on the PCB, I also added an additional Mini USB socket just to have at least one working connection.
The schematic for the tiny ISP programmer
Except for the programming header I used only SMD components, mostly 0805 sized. The board itself is 12mm x 28 mm, the width was dictated by the size of the USB connector.
Board layout of the programmer. Top side on top, bottom side at the bottom.
The boards were made by Seeed Studios Fusion service and came out great. The bare USB connector works reasonably well, if you add some material to the back of the PCB. Some electrical tape works well, hot glue might also be a good choice.
Front and back of the final board
For the software, the original code from simpleavr works great, or if you use an Attiny 85 instead of the 45, the code from [kerhibar]s great little wire project should also work (Update: In little wire the USB data lines are inverted compared to this schematic. I’ve added updated files below).
With a female pinheader, the progammer can be plugged directly into the target.
If you use the Fusion service with small boards, you sometimes get lots of them
Eagle files for board and schematic
Little wire compatible board and schematic
Update: If you liked this, you might also like my even smaller AVR programming cable.