Random notes & other stuff…

Maxim MAX7219

This chip is a LED driver : this means you can connect up to 64 LEDs (matrix configuration), and drive them from a microcontroller via 3 lines. The chip has segments and digits lines. The digits sinks current, while the segments source. It also has built-in PWM to control the LED brigthness. See :

• max7219 datasheet
• Sample projects using the max7219.