I had some space available on another board I am working on, and I decided to add the ATtiny84a prototype board to this empty space. Putting one of these together is pretty easy, there are not too many components to add:

This board is perfect for working on the bread board since it does not take too much space. The Arduino UNO as SPI programmer can be used to upload the Micronucleus bootloader. The LED was added to determine if the board is in bootloader mode:

Unfortunately the board was not recognized by the computer, and after some troubleshooting I found an issue in the design. I designed this board pretty fast, and made a mistake by doing so. The pull-up resistor was on the D+ line instead of the D- line. I removed the resistor from the board and added and external resistor instead. See below how the sketch is uploaded:

There is still some work to do to the firmware. The current sketch is compiled at 16Mhz, even with the CPU set to 8MHz in the board.txt file, causing the delay to run too slow (example above was 1000ms delay).