All the displays, 4 made with neopixels and soldered by hand
Yeah, the 24x24 one took forever to lay out, glue and solder (6H+)
More than 2 years ago, I spent many hours writing an interrupt written driver for LED matrices that require fast line scanning while you setup the right rows, and even faster per color refreshes where you turn the color on and off depending on how bright you want each color component to be to yield different color mixes. This is explained in more details on my page on Driver for direct driving single to 3 color LED Matrices with software PWM.
Then came in Neopixels which can be individually addressed without fast row scanning, and the Adadfruit Neomatrix library. Those made creating color matrices much more trivial (except for the part where you have to actually build and solder that matrix):
2 row scanned matrices on the upper left, 7x7 neomatrix, another row scanned 32x16 Adafruit panel.
on the bottom row, self built 16x8 neomatrix, and another 12x12 neomatrix
I ended up taking my old Adafruit GFX demo I wrote fro my interrupt driven scan matrices, porting it to Neomatrix (which was trivial) and then extending it. You can find my MatrixGFXDemo code here,
Soon afer, I dug up my Adafruit 16X32 RGB LED Matrix Panel, setup an old Arduino Mega to control it and have enough RAM left to run some fun code (on an Uno memory would have been too tight), it turns out that thanks to Adafruit GFX support, it took very little time to get my same demo working on the RGB Panel.
Here is a video of the demo I wrote on all those different displays:
Here are some things the demo does:
Init displays the same 8x8 pattern as many times as it will fit
The code will then draw lines, rectangles and circles that match the size of the display:
If the display is at least 16x8, it will display the resolution in various ways appropriate to the display size: