I have wired a 5x6 matrix of LEDs to a MAX7221. To test the wiring, I simply set the 7221 into display test mode in my setup() by writing 0x01 into the display test register. If I connect only one column (5 anodes connected together) and disconnect the other columns, it works. It does not matter w…

MAX7221, flicker in display test mode

Paul_B May 12, 2014, 12:22pm 5

Power supply insufficient.

(Or a bogus chip - just perhaps.)