VGA capture

[bruleherman]

Hi, I wish just merge RGB signals (via resistor), and have something like:
0-253 -> grey scale
254 -> HSync
255 -> VSync
Send the stream to USB
Read the stream via VLC or similar.
It's just for BIOS and maximum resolution 800x600.
Allow me to debug boot, not need VGA screen, capture to publish on youtube.
Then 480Kbps on serial max.

[MicroController]

You want to convert about 800*600*60=28,8 million analog values per second to digital?
Sounds like you want to purchase a "VGA capture card".

[bruleherman]

Oups, I forgot the 60FPS... just 1FPS it's well for me.
All the VGA capture card I tested into market is not able to capture BIOS (500USD to import here, then I search cheap solution)... and when OS is loaded I have other way to capture.

[Sprite]

You being ok with 1fps is not going to help, your VGA port is gonna output >60FPS regardless.

The way I could see it working is by using effectively an external flash DAC. Take the RGB values, feed them into a comparator with the other end set to 0.35V (half the 0.7V a VGA signal would be at max when terminated with the required 50 ohm resistor) and you have a 3-bit RGB value. Feed that plus the H and Vsync into e.g. the PARLIO peripheral of a modern ESP32 or the LCD/CAM peripheral of an older one (anything that can use DMA to sample GPIOs effectively), dump that stream to PSRAM, and sort out the actual way the image looks later in software. It's a lot of software work to sync that up properly, I'd imagine.

[bruleherman]

Then working VGA capture card working with BIOS take me lot of time and 5200USD... I think it's more cheap with ESP32 just grab 1Bit for each color, reduce to 1FPS, and send frame by frame to serial. After it's just simple software displaying raw image.