This was once available in kit form at https://adwaterandstir.com/product-category/parts/, but it has recently been unlisted from the store. Instead, we will have to source the parts ourselves based on the source files. Easiest to obtain is the PCB, which can be simply ordered from OSHPark1). A BOM is included below (carefully note package dimensions!).
| Part | Quantity needed | |
|---|---|---|
| 22 pF, 2.54 mm | 2 | DigiKey |
| 22 nF, 2.54 mm | 1 | DigiKey |
| 100 nF, 2.54 mm | 6 | DigiKey |
| 150 R, 1/4 W | 1 | DigiKey |
| 1 k, 1/4 W | 1 | DigiKey |
| 2.2 k, 1/4 W | 1 | DigiKey |
| 10 k, 1/4 W | 3 | DigiKey |
| 47 k, 1/4 W | 1 | DigiKey |
| 100 k, 1/4 W | 1 | DigiKey |
| 1 M, 1/4 W | 1 | DigiKey |
| green LED, 2.54 mm | 1 | DigiKey |
| ATMega328P-PU, DIP-28 | 1 | DigiKey |
| 74HC126, DIP-14 | 1 | DigiKey |
| CD4068BE, DIP-14 | 1 | DigiKey |
| 74HC00, DIP-14 | 1 | DigiKey |
| 74HC04, DIP-14 | 1 | DigiKey |
| LM358, DIP-8 | 1 | already in stock |
| 8 MHz crystal, HC-49S 2) | 1 | |
| 3.5 mm audio jack | 2 | AliExpress |
| 1×3 pin header | 7 | DigiKey |
| DIP-8 socket | 1 | DigiKey |
| DIP-14 socket | 4 | DigiKey |
| DIP-28 socket | 1 | DigiKey |
| SBH11-PBPC-D13-RA-BK | 1 | DigiKey |
As all parts are through-hole, assembly proceeded simply enough. The most complicated portion was programming the ATMega chip, something we had never done outside of Arduino programming. We used the Raspberry Pi GPIO avrdude configuration and a breadboard. The fun came when programming the fuses3). We set them incorrectly on the first attempt and were subsequently unable to interact with the chip in any way; the same happened when we tried again with another chip and the correct fuse values. This was because both settings — correct and incorrect — told the chip to expect an external oscillator as its clock source. Once we built the required oscillator network, communications functioned normally. If we are to program more AVR chips in the future, it would be a good idea to construct a target board, perhaps with sockets for support components (crystals, capacitors, etc.).
They almost certainly didn't have these back in the day.