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.
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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:
https://github.com/hoglet67/RGBtoHDMI/wiki
Other Atom and video projects from the same source:
https://github.com/hoglet67/AtomGodilVideo
https://github.com/hoglet67/AtomVGAWing

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