[Andy] didn’t want to use up 24 pins on his Arduino, so he used a latch to multiplex the lowest 8 address lines and the data lines together. With the 512KB RAM expansion installed, the Mega is ...

The system is controlled by an Arduino Mega, with the meters driven using the PWM pins. The only extra part is a 1 kΩ resistor. The Arduino wrangles the LEDs as well. Sadly [Lex] did not include ...