Oh ok. I never dig into ESP32 too much.
Anyways, about STM32 is an whole new world. Arduino and such platforms are all based in 8bit chips.
Actually, the ESP32 is a 32-bit dual-core MCU. It's still easy to get it working especially if you get it on a 'dev board' such as a D1 mini, because then it has USB built-in with USB-UART converter chip on the PCB, as you can see in the images.Anyways, about STM32 is an whole new world. Arduino and such platforms are all based in 8bit chips.
Ok, hope you keep improving on your design and features of your project. I'll keep taking a look to this thread!
Thanks for sharing!
Sure, glad you guys like it Thanks for sharing!
I've considered doing this myself before, but just didn't get around to it. Considering that ready made products are very expensive, a few hundred quid. I've always wanted to put something like this together, I don't need it to be fancy looking, just needed something to satisfy the nerd in me.
Can't agree more! 
How easy would this be to scale? For example, making it bigger? I know we're talking about elevated costs then, but if buying these panels in bulk, it could be a little fun project for a wall 
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In theory, it should be relatively easy. The README implies that for vertical scaling it might involve a bit of custom calculations, but it should just be a matter of a division and a modulus. Like, if the library really doesn't support vertical scaling, you just set it up as a long horizontal 'chain' and calculate coordinates of the real thing in your own code.. Quote from: https://github.com/2dom/PxMatrix#chaining
Chaining any number of displays together horizontally is rather straightforward. Simply use the supplied flat band connector between the panels and then treat the entire chain as one display.
Also, would be pretty sweet to be able to turn it off at a set time, I'm also thinking that connecting it to one of those remote controlled plugs could satisfy the nerd in me even more.
You could easily code that in, add a little HTTP listener to turn the thing on or off via API calls or just put it on a ready-made 'smart plug' or IR controlled plug (for better privacy and vendor- / app-independence).I think I'll order 3 more to get a 2x2 display; should be a nice size and would allow me to play with the horizontal and vertical scaling.
Unfortunately, they jumped in price from ~20€ to ~30€ from what I can tell.
It's cool that you explained everything in so much detail, now I have it all figured out.