ULAdigitizer

This board is added to the underside of the ZX Spectrum 16k/48k home computer. The FPGA on the board listens to the digital communication between the ULA and the rest of the system and re-generates the video output in a near-digital form. This output signal (we call it 'lumacode') can then be flawlessly upscaled to a pixel-perfect HDMI signal using an RGBtoHDMI device or some other device that can decode lumacode.

The original video output of homecomputers of the 1980th is of pretty low quality. Using a modern TV to display this signal normally does not make this any better. In fact it normally just exaggerates the visible noise. Also there is basically no way to improve the analog signal because of the random nature of the noise.

With my digital-only approach, the monitor picture is absolutely perfect without any noise or ghosting.

This mod only works with the variants ZX Spectrum 16K/48K and ZX Spectrum+. Later variants use a different ULA which is not compatible. But these machines provide either digital RGBI or analog RGB on their video port. These signals can be directly used with a suitable RGBtoHDMI.

More details are available on the project documentation page.