Allright! Horizontal scrolling works now I have to make it nicer now because it does not clip tiles yet.
It's very very hackish. I modify the frame time for the back and front porch to get scrolling. I can scroll smoother than per pixel this way

I modified the ASM of the video driver. It did have scrolling out of the box, but since the video driver takes tiles I have to use some accurate code to be able to scroll with clipping. In the V axis that is not a big problem. Just set the video counter to the offset multiplied by the horizontal tilecount and there you have your vertical scrolling, but horizontal is a bit more tricky and it involves messing with the video scale register in real time (it contains timer values).

The video generator can only assign 4 colors per pixel per tile and to shift the tile grid you need to shorten a tile on the left and shift in another tile that is 16 - the size of the leftmost tile in pixels. To do this you set the video timer so it fetches new data after for example 7 pixels have been drawn. Then switch back to 16 pixels and draw the other tiles like normal. Then do the last 9 pixels using the same trick I used on the leftmost tiles.

So this is what happens:
do visible porch line
while it draws that: set video timer to 7 pixels
tile0 << 9 (leaves you with 7 more pixels)
send shifted tile data to video generator using the WAITVID instruction
while it draws that: set video timer to 16 pixels
do all of the tiles in the middle
at the last tile you set the video timer to 9 pixels
tilex << 7 (leaves you with 9 more pixels)
do visible front porch line

repeat for all lines you want to scroll horizontally.


I have not implemented it this way yet though. I am focussing on school at the moment.

It's all about racing the electron beam: Decrease tile size at the front, draw all the tiles, fill in leftover space at the back. That is how it shifts.

I just hooked up a commodore 64 keyboard to the eZ8 computer. The c64 keyboard is just a matrix of switches like this:
It's really easy to read individual keys.


Should be able to make some interactive software now

I just managed to read every single keypress event. The cpu store all key states in registers. That way it knows which keys should not cause a trigger because they are held down. I am now gonna write a simple typing demo I guess?

Edit:



I recorded some footage using my video capture card. It shows how it reads key input from the c64 keyboard.
The first byte is the column number. The second byte corresponds to the bit of the pressed key.
Example:
Key E is 0x02_40 because it's the 2nd column and it's the 6th key, so 2^6 = 0x40

Working on a string parser. I got this down already:
-User input
-Keyboard string gets stored
-Tokenizer for single tokens

To do:
-Tokenizer that takes a string and converts all the words into tokens.
-Token interpreter.

It sounds awesome but unfortunately I can't watch the video.