NES vram buffer sample

[mickbeaver]

Hello,

I have been following along with the projects using my local build environment (CC65 and the Mesen emulator). I found that the VRAM Buffer sample had some odd behavior where the Y scroll position jumped all around. At first I chalked it up to my local emulator, but I was able to get it to happen in JSNES, too, by increasing VBUFSIZE to 150.

As far as I can tell, the issue is that the scroll register isn't getting set during the vblank period, as the local variable y and the NESLIB variable SCROLL_Y seem correct.

[mickbeaver]

In other words, the bug that I'm trying to report is that the timing of the sample is extremely sensitive and that other emulators, such as Mesen and Nesicide, show scrolling artifacts at a lower VBUFSIZE (such as 128).

[denisenepraunig]

@mickbeaver oh I see you've setup the project locally!

I struggle quite a bit with my setup locally, may you could give me some hints how you did it?!

1. Do you use a cfg file for the CC65 compiler like nesdoug does?
2. Where you able to link the sprites (//#link "chr_generic.s") into the NES ROM?

Here is a little thread, but couldn't get it working... https://twitter.com/denisenepraunig/status/1454445239389806594?s=20

Many thanks in advance!

[mickbeaver]

Hello,

For prerequisites:

• CC65
• GNU Make
• NESlib from https://github.com/sehugg/neslib.git
• 8bitworkshop from https://github.com/sehugg/8bitworkshop.git

You can download chr_generic.s and create an object file out of it. The linker config is in 8bitworkshop/src/worker/lib/nes/neslib2.cfg.

I've attached the code; can't remember what state it is in.

mgftn.zip

[denisenepraunig]

@mickbeaver Thank you Mick for sharing your files and config - now I found all the files I need, compiled the crt0.s and things like that. Now it works for me! 👍 YAY finally 🎉

[mickbeaver]

You're welcome! I remember it being a bit of a mystery... Specifically, having a custom NESlib was a surprise to me.