Multi-Breadboard Drifting! (555 timers and such)

From the YouTube video comments:

“I modified the earlier sketch that draws characters on the led matrix to count from 0-9 (then loop back), and i triggered it with a 555 timer circuit i made earlier.  555 timers can be used as pulse trains. always keep at least one on your giant table-sized breadboard!”

The display used here is the DLG7137…