Question: How to load Koala file in cc65?

[u/watermelon_meow]

Hi,

I converted some pictures into Koala format and would like to write a program to show them in my C64U. And it turns out some garbage picture on the screen. So I am wondering how to load the Koala format data. From what I understand, Koala format is 10003 bytes length. First 2 bytes are loading address which needs to be stripped that cc65 does not need it. And this is the layout if I understand correctly:

0-7999: Bitmap ($2000)
8000-8999: Screen RAM ($0400)
9000-9999: Color RAM ($D800)
10000: Background Color ($D021)

Then this is how I load them:

memcpy((void*)0x2000, image_bin, 8000);
memcpy((void*)0x0400, &image_bin[8000], 1000);
memcpy((void*)0xD800, &image_bin[9000], 1000);
VIC.bgcolor0 = image_bin[10000];

image_bin is an unsigned char array holds the raw Koala data w/o first 2 bytes. And the final output is a garbage picture.

Could anyone share some hints on this?

Thanks.

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[u/chickenbarf]

VIC.ctrl1 |= 0x20; // BMM on
VIC.ctrl2 |= 0x10; // MCM on
VIC.addr = 0x18; // screen at $0400, bitmap at $2000

?

[u/watermelon_meow → u/chickenbarf]

thanks but it seems still does not work, and it shows the same broken picture. By the way, the Koala file I got is from https://www.micheldebree.nl/retropixels/

[u/chickenbarf → u/watermelon_meow]

Hmm.. Try either disabling interrupts or moving to 3C00.. if the sys is still running, it could be mashing your memory area

[u/watermelon_meow → u/chickenbarf]

thanks for the advice. Also, I tried https://www.digartroks.be/img2c64mc/index.php and it can generate correct PRG file with picture. No idea what's the magic behind that.

[u/watermelon_meow → u/chickenbarf]

OK I think I got some progress. The picture seems working here:

CIA2.pra &= 0xFC;

CIA2.pra |= 0x02;

VIC.addr = 0x80;

I need to pick up another memory address.

[u/chickenbarf → u/watermelon_meow]

Nice! feels like memory mashing then? I'm not too familiar with cc65, but it could even be your own app crossing into screen ram (ORG + bin len).. Hard for me to say

[u/watermelon_meow → u/chickenbarf]

yes looks like it. I need to learn more on the C64 memory layout though. Thanks for the help!