Max7219 dot matrix display: clock, calendar, and memo board.

I used a Wemos D1, to drive the display. This is an ESP 8266 chip on an Arduino Uno form-factor board. I wrote the code using Arduino IDE and tested it using a Nano, but then swapped to using the 8266 to take advantage of the Web connectivity. You could also use an ESP 32 - the code runs on that too - but you need a power supply that can deliver about an amp - either on 3.3V or 5V - if you want to light up lots of the LEDs at full brightness: most of the ESP 32 offerings don't have that sort of power supply built in. The Wemos D1 boards are also dirt cheap. Total parts cost for the contraption is about thirty dollars on Ali Express, as of October 2020.

You can download the sketch here: https://ceptimus.co.uk/DotMatrixMemoC...

...and the STL files here: https://ceptimus.co.uk/DotMatrixMemoC...