This week, Acorn's Atom gets HDMI output and shows it really has 12 colours including three shades of orange. (Generally it's regarded as a 4-colour machine with a choice of two palettes, but it turns out the text and graphics modes have slightly different shades available.) The HDMI output in this case is by means of a Raspberry Pi, with a CPLD middle-end to capture the pixels, and an analogue front end to digitise the Atom's non-binary output levels. The same kinds of techniques might well work with an Amstrad CPC.
The original Atom colour board was quite tricky, and there are later and modern designs which do a good job of removing the video-contention noise and producing good levels. The thread is well worth a read! Here's the intro post:
"""I thought I would start a new thread to record my experiences with various Atom colour boards. Since I got my Colour Atom a few weeks ago, I've tried several different ways of getting a proper colour picture:
- The original Acorn colour board that was fitted with an RGB output
- Phill's new design (based on the LMH1251) with an RGB output
- Using Y PA PB on connector PL4 directly as a YPrPb output
- My own design, that I've been playing with this weekend

The RGBtoHDMI project also works wonders for a BBC Micro, as well as for a ZX Spectrum:
Other Atom and video projects from the same source:

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