This is just a quick blog post to say that I have revised my plan for this project a little.
I have decided to make the computer use 32K or 48K of RAM.
I have found a cheaper 4G cell breakout board than the one that I originally specified.
I have also decided not to go with the Hobbytronics open source serial-to-VGA video driver, and instead use the TIA from the Atari 2600 as the video chip for the computer.
The following is the implementation of the TIA in the Atari 2600, which uses the TIA to generate a composite output, which is then combined into an RF signal.
And I will draw up schematics showing how I will change this circuit to display composite video and monoaural audio.
The TIA is a very versatile device which is capable of 128 colours in NTSC video, with one colour per scanline. With special coding, it is possible to draw up to 36 columns of text.
See THIS forum post and THIS blog post for more details.
This is an example of the text display. This is 36 columns. I think it is possible to go further.
And another example of text display on the TIA. This is 24 columns:
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