I learned how to write an ISR

• I learned how to write an ISR
• Cannot use Serial.printf in ISR, and must be fast. Debugging is not easy.
• Need to use volatile to share a global between ISR and main code.
• Instead of firing 16 interrupts and light up a color 0 to 15 times, there is a technique called BCM
• Binary Code Modulation changes the interrupt frequency to fire only 4 times instead of 16, but with intervals 8t, 4t, 2t, and t.

Row Scanning Driver Details