this is a small box and lid that will hold (2) 8X8 LED arrays.
These LED's have the MAX7219 chip on board
They measure 32mmX32mm so two measures 32mmX64mm
8X8 LED's so two = 8X16 LED's
replace ‘prog_uchar’ with ‘const unsigned char’ in the sketch then it will work
R1 I made a revision. This box and lid will hold 4 units.