Page created: 15APR2026
Over the past month or so, I drew a schematic and designed a PCB for this project in KiCad, then had it fabricated by JLCPCB. Nearly two weeks passed while the boards were being fabricated and shipped (the manufacturing takes 2-3 days, but the cheapest shipping option brings the wait up to about two weeks). I assembled a board and put together the prototyping setup. The disc drive and ATAPIctrl board are powered through a splitter by a cheap power supply with a molex plug that outputs +5V and +12V. A USBasp programmer is connected to the SPI programming header, which will be the means of uploading the firmware to the board. On the breadboard is a FT232 module (wired to the transmit, receive and ground pins of the ATAPIctrl), which is a USB to UART adapter that will allow me to communicate with the ATAPIctrl over USB from a terminal emulator on my laptop.
I designed the ATAPIctrl board for an ATmega8515 chip in a DIP package as this made the trace routing easier (routing lots of signals from a large connector to a tiny chip is a pain, and many signals conveniently just lined up when using the larger DIP part). I instead installed a TQFP-44 package on a DIP breakout board I made because the TQFP-44 variant was easier to acquire. I did not install a crystal oscillator and load capacitors (parts Y1, C2, C3) for now as I want to get this working with the ATmega8515's internal clock source first. I implemented those footprints as insurance in case I need to run the 8515 at a higher frequency than the internal oscillator.
The quick and easy part is complete. Now comes the long process of writing the firmware...