VGA through rpi pico - How many colors possible on border?

[Brocky]

this is cool...finally a converter that works!..gonna have to get one...

i wonder if this could be simplified with something like an ESP32 WROVER and its ADCs and inbuilt comparators... i know it can output 64 colour VGA..

[eto]

Yep. I had test screen appearing on power off after a second in earlier version but it was causing some issues, so I switched it off and did not fix yet.

would turning black/off be a possibility? Test screen after power on is fine, but if I turn off the CPC it's a bit misleading to see the last frame.

Scanlines should be easy to add... instead of doubling each row I would just put every second row black?

It's worth giving it a try. Or maybe half brightness? Of course that would require another resistor per colour and another PCB revision.

The case looks awesome! It that case 3d printed? Is there a chance you would share the design?

Sure. The one you see in the picture is a special one as I pass through the power and can turn on/off everything with a switch. I also made another version which is just the case for the converter without any additions. I did not test it yet though... I'll make a test print today and share it.

[eto]

Is there a chance you would share the design?

Find attached the STL. I'm not 100% sure that it will fit as I can't test it as my converter is already fully assembled and I don't want to tear it apart again. But I think it should be fine. 

One version for the top of the case is for the pure PCB and the other is the one I used which offers options to add a power connector, power outlet and a switch. Not sure if anyone else will use it as I designed it for the components I already had. 

For the cords I also made some strain reliefs. I am absolutely not sure if that is a good design but it works for me. Put the cable through the hole before soldering it internally (check that it has the right size - there are 3 different diameters). Adjust the length so there is not too much cable inside and then press the little part into the slot - this should keep the cable in place and secure the internal soldering from any accidental ripping. 

[Brocky]

this is cool...finally a converter that works!..gonna have to get one...

i wonder if this could be simplified with something like an ESP32 WROVER and its ADCs and inbuilt comparators... i know it can output 64 colour VGA..

im just looking at the pinout on the rpi pico...  it seems it has 3 ADCs... wouldnt they be perfect to read the RGB values from the CPC instead of the dedicated comparators?
the ADCs will be able to determine the levels and you can code them appropriately...
https://microcontrollerslab.com/raspberry-pi-pico-adc-tutorial/

im gonna have to grab a few picos to play with!

EDIT: never mind ..found the answer "First I wanted to use ADCs in RP2040, but they are just too slow."
96 clock cycles x (1 / 48MHz) = 2 μs per sample (500kS/s). for one conversion..we need 3x that...
ESP32 ADCs are not up to the task either

[gregg]

Unfortunately ADCs in pico are just too slow. I wasn't able to read samples fast enough with them. Actually that was also quite hard to find fast enough comparators that were cheap in the same time.
But if you find any way to do it without comparators, that would be great. It would simplify the design a lot.