(resolution > 200x200, colours >15)
The explanation of Nick Gammon for VGA shows that with a standard 16MHz clock the max nr. of horizontal pixels for 60Hz VGA is about 160. As said before for CVBS using the AD725 chip (and 14.31818MHz) we have a max of 104 horizontal pixels. However NIck Gammon shows the number of pixels depends on the refresh rate of the video mode. I am wondering if there are refresh rates far below 60Hz... have searched, cannot find them.
So options I see are:
- Solution to buffer writing pixels like a Pi Zero or a chip like the VLSI VS23s010C-L which does this
- Lowering my specs from 200x200 to below 160x160
- Higher crystal to drive the ATMega chip
The VLSI VS23s010C-LVLSI VS23s010C-L is (as expensive as the Pi Zero and) very difficult to get. European distributors don't have it in stock.With my limited knowledge, I am not able to find a suitable alternative on the web or on ebay. Suggestions are more than welcome!
EDIT: There is another option and that is the use of an Arduino Due with the DueVGA library. An Arduino Due is not that expensive on ebay (about $13). Advantages this has:
- same Arduino programming IDE (as opposed to Pi Zero)
- high res 320x240 in 255 colors
- VGA and Composite possible
- easily available
- feels not like cheating with an overpower board like the Pi Zero which also could emulate the other chips of the 8 bit system.
SIDENOTE: I examined whether VGA or Composite is more future-proof and found that with tv-monitors above $500 most have composite but no VGA.