The Firmware & Bootloader
Clicking on the "Firmware" link on the left-hand side of this page goes to a zip archive containing the firmware (code - an Arduino sketch) for the computer as well as the Arduino libraries required for the sketch. Once the zip archive has been downloaded, extract it and place the folders within the "Arduino Libraries" into the Arduino libraries directory as shown in the image below:
Once the Arduino libraries have been placed in the correct directory, the Arduino sketch needs to be placed in the Arduino sketches directory as shown in the below image:
After the firmware folder has been dealt with, the bootloader can be downloaded from the "ATmega 1284P Arduino Bootloader" link (which goes to a Github page; use the download as zip link on the right hand side of the Github page) and placed within the Arduino hardware directory as shown in the following image:
Once both the bootloader and the firmware files have been dealt with, the Arduino IDE can be opened. Open the "AVR_BASIC_Computer_V0.1" sketch and then select "Original Mighty 1284p 16MHz" from the board menu (Tools -> Board). Then select the "USBasp" from the programmer menu (Tools -> Programmer) or alternatively "Arduino as ISP" if an Arduino is being used. Pinouts for the USBasp header on the PCB can be found by googling "USBasp pinout" (I have marked the ground connections on the PCB). The below images show these steps:
Finally, connect the USBasp programmer to the assembled circuit (along with a power source) and select "Upload Using Programmer" from the file menu as shown in the below image:
Done! Now the computer is programmed and ready to be used. Simply connect a keyboard and composite display (such as a TV) to begin writing BASIC programs.