niklasekstrom/flickerfixer

An open source flicker fixer for Amiga 500/2000

flickerfixer

An open source flicker fixer for Amiga 500/2000

This is the first stage in the construction of a flicker fixer/scan doubler that mounts internally in an Amiga 500 or Amiga 2000.

In order to rapidly prototype the FPGA logic I designed a small adapter board that connects pins on Denise to a DE10-Lite FPGA development board via a 5V-tolerant buffer. The KiCad files for the board are available in Hardware.

After ordering, receiving and soldering the PCB I then wrote Verilog code that samples CSYNC (composite sync) and the 12-bit RGB signals, and outputs the sampled pixels to VGA. The logic handles both non-interlaced and interlaced output from the Amiga. The Quartus project is available in HDL.

The next stage is to design a stand-alone board that contains an FPGA chip and an SDRAM chip.

Some pictures:

flickerfixer's Issues

Try finding top-left corner of display window from PIXELSW pin

Denise has an output pin PIXELSW that is supposed to indicate if a pixel has the background color or not. It might be possible to use this pin in some clever way to find the top-left corner of the display window (DIWSTRT), which could be used to remove overscan and only output the pixels in the display window. Probably one has to make additional assumptions about the size of the display window for this to work, which may only work in certain circumstances. Experiment!