The interrupt part isn’t that difficult at all once you’ve wrapped your head around it. I guess mostly all the register names are confusing at first, what they do and so forth. Having a look at the datasheet for ATmega168/328 should answer most questions regarding that.

You can play with all numbers in there. Assuming nothing else is plugged in, the worst that can happen is erratic behaviour or a blank screen ;-)

Seems like one of your last comments was caught by the spam filter. I didn’t check for a while, but now it’s online. Strange that I didn’t get an email from my blog…

So an ATmega328 should be able to hold way over 100 images, depending on how much other code you put in there. Image complexity doesn’t matter.

Regarding colors, the standard code runs a color depth of 5bits per color, which totals in 32768 shades. However, many of these will look the same to the human eye. The converter script has a variable called $color_scaler, which is set to 8. 24bit images allow for 255 shaded per color. That gets divided by 8, which gives about 32.

Strongly contrasting colors work best.

#define __fade_out_display 2000 // in milliseconds

To run stand alone animations, the loop function of the arduino code should look like this:

void loop(void) {
/* this would show the images stored in the above PROGMEM arrays
byte counter;
for (counter=0; counter<10; counter++) {
show_image(counter,100);
}
}

There’s already an animation stored in the code, consisting of 10 frames.

To convert your own .ppm images, use ‘convert_ppm_to_array.pl’ on the image. It will spit out c-code, which you can put into the arduino code in the same manner as shown in the little demo.

The images must be named like ‘frame1.ppm’ etc, so the converter knows how to number the arrays for the c-code. Be sure to also adjust

const char * frames[] = {frame1,frame2,frame3,frame4};

accordingly.

I create .ppm images using GIMP like this:

Create a new image with 8×8 pixels, draw draw draw, save as e.g. “frame5.ppm”, chose option: RAW.

BTW, I hope you use the code I’ve published on my gitweb site. Anything else should be pretty much obsolete.