ECE 110/120 Honors Lab Section : 8 Bit Console

Purpose: Our primary goal with the project is to further our understanding of how a simple CPU operates. We will use the NES processor as our subject and study graphics rendering and assembly programming. In addition, we want to study how other components work in conjunction with the CPU, such as the buses, storage units, and clocking. Our second goal is to create a functional game console using an 8-bit processor with the help of a Raspberry Pi with the NES as a base. 

We are all fans of retro computing and especially, retro gaming. The opportunity to work with a retro console and to study how computers work in general was something we were not going to miss. This project is important to us because we will not only be just simply coding a video game but we will be able to work on the hardware itself, as well. 

Background research:

Throughout our classes, we learned about the core components of a computer and how they interact with each other. We also learned high level programming and assembly language programming. While this may not be enough to build our project, we are confident that it will give us a strong foundation as we do more research on building a more simple computer. 

 There are several examples online of engineers developing their own versions of retro 8-bit consoles. Here is one from Sergio Vieira:

There are a huge amount of examples of building simply a "homebrew" 8 bit computer, the most famous being Ben Eater.

There is a wealth of information about both the NES layout and wiring, specifically an entire wiki about developing for it. In addition, the whole manual for the 6502 assembly language is available online.

Block Diagram:

• PSU: Will most likely be a 5V source to power the Raspberry Pi, CPU, and PPU.
• NES Game: We will choose a NES game to test our console. The NES cartridge contains game ROM and RAM.
• Controllers: Will either be NES controllers (real or clone) or of our own design.
• PPU: The Picture Processing Unit was the main IC on the NES to process and output video.
• CPU: We will either use the NES CPU or the more common Commodore 6502 CPU.
• Raspberry Pi: We hope to implement a Raspberry Pi to either replace or aid the PPU in video and audio processing. We also hope to output video in HDMI.

Parts Needed: 

• RP2A03 CPU, Ebay (Not on Amazon) ~$24 
• NES PPU Ricoh RP2C02, Ebay, combo with CPU, $29
• Raspberry Pi 4, Adafruit ~$35
• NES game cartridge, ~$20 (varies depending on game), Ebay or Gamestop
• 6502 CPU, ~$5, various places, will ask for advice on which is best to order from
• Breadboards, ~$5, ECE Supply Center
• Wire, purchased by the spool, various colors, ~$1 each, ECE Supply Center
• RAM Chips
  • EEPROM
    • 6502: AT28C256, 256K, ~$10, digikey
    • NES: Uses two of these, 32k for prog, and 8k for chr
  • SRAM
    • 6502: 62256 SRAM, 256K, ~$3, digikey
• Various other IC components that can probably be picked up from ECE Supply Center

Possible Challenges:

• Breadboard will get cluttered quickly and keeping track of everything may be difficult 
• Designing a proper PCB to hold components
• Integrating the Raspberry Pi with the RP2A03 processor
• General programming with the processor

References:

[1] "CPU", [ONLINE]. Available: https://wiki.nesdev.com/w/index.php/CPU. [Accessed Februrary 14, 2020].

[2] S. Vieira, "Building a 'homebrew' video game console", [ONLINE]. Available: https://www.gamasutra.com/view/news/338966/Building_a_homebrew_video_game_console.php. [Accessed February 14, 2020].

[3] B. Eater, "Build an 8-bit computer from scratch", [ONLINE]. Available: https://eater.net/8bit. [Accessed February 14,2020].

Other Links:

http://www.6502.org/