A small test sketch turning a row of LEDs on and off for periods of 1 second showed the problem clearly. Touching the pins of the LED drivers often provoked or stopped the problem temporarily.
Whilst investigating I found no functionality that controlled the enable pin of the LED drivers (pin 21) although they are connected to digital pin 9 of the processor. Setting that pin permanently to LOW in my test sketch appears to eliminate the problem
I see in the library file that there are macros
Code: Select all
/* Macros for the LED driver enable pins */
#define DRIVER_EN_HIGH PORTB |= 0b00000001;
#define DRIVER_EN_LOW PORTB &= ~0b00000001;