Review on GeeekPi 2Pack MAX7219 8x32 Dot Matrix MCU 4-in-1 LED Display Module for Arduino & Raspberry Pi - Red Color by Melissa Perez

They were easy to get working with Arduino Nano, Uno and ESP8266 NodeMCU microcontrollers. I haven't tried them with a Raspberry Pi yet. I have found that there are at least 2 variations of this product. The first version has gaps between the 8x8 LED arrays and the board with the MAX7219 chips installed on them, occupying an additional 1.5-2 rows on the breadboard. The markings showing IN -> OUT -> are on the top of the board, making it a bit difficult to figure out which end to place the wires on. The other has no gaps between the 8x8 LED arrays and is labeled IN -> OUT -> on the underside of the board. I don't know which would be considered the current version. Another potential caveat is that the pin headers are at a 90 degree angle. If you want to splice two of these modules back to back (like I did) you will need to desolder the pins and solder on the straight pins to replace them. Another advantage of the straight headers is that the product can be installed on one breadboard (but spans three breadboards) without soldering. I would like to order more of these pins, but the possibility of a **third** hardware variant confuses me a bit. I'm afraid to do this.