SNES for MiSTer by srg320
Ported to ULX3S using Yosys+ghdl+nextpnr+trellis
Requirements
- ULX3S 85k
- Latest Yosys, ghdl, ghdl-yosys-plugin, nextpnr and Trellis
- SNES ROM(s)
Building for ULX3S
Flash some SNES ROMs using fujprog. ROMs start at address 0x200000 and are spaced by 0x100000. (the start offset in 0x100000 units is selected by DIP switches [3:1]). ROM type and size is auto-detected, plain 'smc' format ROMs should be used.
Currently only ROMs without DSP or SA1 work correctly.
Run the following commands to build and program:
cd ulx3s/scripts
export PLUGIN_DIR=/path/to/ghdl-yosys-plugin
bash build.sh
fujprog-v42-linux-x64 snes.bit
Set DIP switch 0 to select PAL or NTSC, and use DIP switches 3..1 to select the ROM starting offset in flash. Connect an HDMI monitor or TV capable of 640x480 to the ULX3S.
The button mapping is as follows:
- Direction buttons: SNES direction PAD
- Fire 1: B
- Fire 2: Y
- Power: START
- Fire 1 + Fire 2 + Power: RESET
Other SNES buttons are not mapped and would require an external controller (see Known Issues.)
Simulating using CXXRTL
A 512kB, LoROM, no enhancement chip ROM is currently required (Super Mario World is recommended).
Run:
cd ulx3s/scripts
mkdir snes_frames
python ../util/conv_rom_to_hex.py my_snes_rom.smc > rom.init
bash simulate.sh
To convert the CSV format frame to an image, run:
python ../util/convert_frame.py snes_frames/snes_frame87.csv frame_out.png
Note that CXXRTL simulation requires very recent Yosys and G++.
Known Issues
- Audio is output to the 3.5mm connector, but is currently distorted and broken
- DSP enhancement chip is included in the build, but doesn't seem to function correctly
- Currently a framebuffer is used to match the SNES video mode with HDMI. This increases BRAM usage and latency. If a suitable mode could be found and adapter module written, a linebuffer approach would be better.
- Hires video mode is not supported.
- External controller support is needed to enable all buttons of the SNES to be used.
- Loading ROMs from microSD or over WiFI via ESP32 would be easier than programming them to SPI flash.