Atmega328 game system with 6502 emulator

ATMEGA328 GAME SYSTEM WITH 6502 EMULATOR FULL
ATMEGA328 GAME SYSTEM WITH 6502 EMULATOR SOFTWARE

An assembly routine mixes 4 audio channels and fills up another buffer during vblank. After pulling in tile indices from RAM and tile graphics from ROM, there is hardly any time left to do sprites.ДЄudio is double buffered, so that at the start of each scanline video generation routine pulls a byte from an audio buffer. I had to painfully cycle count the scanline routine so that it fetches tile data and masks sprites on top of the scanline while outputting a pixel every 6 cycles. The hardest part was getting sprites to work. Here's a few things worth mentioning to maybe get you an idea what's going on: The code is in a pretty messy state because of many optimizations and because I wanted to release the video as soon as possible. Just give me a few days to clean up the code and add the playback routine.

The AD725 datasheet has a reference schematic for the oscillator, or you can simply use a crystal oscillator like I did, although they are more expensive and maybe harder to find. The chip needs a strong (buffered) clock signal. Nick, a crystal can't directly produce the needed frequency for the AD725. Thanks for the interest and kind words! They make the endless hours spent on the project worthwhile :)

ATMEGA328 GAME SYSTEM WITH 6502 EMULATOR FULL

IвЂ™ll probably do a full write up with schematics when music is done if people are interested in this. For example room data is compressed in flash and inactive rooms use only 1 byte of RAM to store the state of objects when the player is not around. The game is fully playable and has 15 rooms.ДЄtmega328P has only so many bytes of memory, so several tricks are needed to squeeze everything into memory. This should allow C64 SID quality music once the playroutine is finalized and music is composed.

ATMEGA328 GAME SYSTEM WITH 6502 EMULATOR SOFTWARE

RGB values are converted to NTSC composite signal by AD725 chip.ДЄudio is generated in software by mixing 4 waveforms together. The program has been heavily optimized and written in assembler, so that the ATmega328 outputs a new pixel exactly every 6th clock cycle.

Video signal is generated by the microcontroller by outputting 8-bit RGB values. Music is still work in progress and not present in this early video footage. 4 audio channels with triangle, pulse, sawtooth and noise waveforms. Display resolution 104x80 with 256 colors. Up to three sprites per scanline, unlimited number of sprites vertically. The project is not yet finished вЂ“ IвЂ™m working on music playback which is still missing on the video.ДЄttached images: titlescreen, arduino based proto version, final standalone hardware. ItвЂ™s a 8-bit retro video game based on Arduino and ATmega328P. IвЂ™m finally ready to show you a project IвЂ™ve been working on and off for several months. Visit my blog at for schematic, source code and technical info!

Atmega328 game system with 6502 emulator