The first shield I'm going to make is a standard 8×8 matrix with red LEDs, using the IS31FL3728 chip. What's the difference from the HT16K33-based one then? Well, not much. It's still "on/off" only for each LED, with a global brightness control. There are two extra features, related to the analog input pin that this chip has: you can modulate the brightness of the whole matrix according to an audio signal, and you can switch it into "equalizer mode" -- not sure what it does then, but you can guess.

I have the PCBs already, and I should get the chips on Monday. I will need to do some tricky QFN package soldering then, but I have a couple of tricks that should work.