Example four-digit 7-segment display project for the Sipeed Tang Nano 4K, includes a "shift-and-add-3" binary-to-BCD encoder for displaying in base-10.
The example assumes a common-anode 7-segment display where the 4 digits share the ABCDEFG cathodes:
Pins 13, 17, 18, 19, 20, 21 and 22 are connected to segments A, B, C, D, E, F and G respectively.
Pins 35, 34, 32 and 31 are connected to the anodes of digit 4, 3, 2 and 1 respectively (where digit 1 is the least signficant, digit 4 is the most significant). Consider using a current limiting resistor for each anode.
