I am attempting to design my own custom PCB for a TKL layout with 12 extra macro buttons to the left. In total it will require 100 rgb leds. I think I'm gonna use the at90usb1287 (48 GPIO pins) but it's up for change.
My keyboard matrix, with some space saving hacks, I calculated to take up 17 cols + 6 rows = 23 pins. That leaves 25 pins to address 100 common anode rgb leds.
For reference, here is the layout:
https://imgur.com/a/zRkqr6MThe matrix has 1 column less because I managed to squeeze the navcluster + bottom right modifiers into 2 cols.
Since each color of each led triplet should be individually addressable, we're really dealing with 300 outputs.
So far, I have looked at 1:16 demuxers but that would still take up too many pins. Big Demuxers, of 128 and larger I'm not able to find for a reasonable price. I also wasn't able to find shift registers which do pwm, and chaining them would cause too much delay anyway.
Are there chips that do this? And what are they called? I tried searching for "RGB LED driver" but all I could find were those sh*tty led strips, or those smd rgbs with built in controller. How do other boards do this?