/challenges-projects/design-challenges/energy-harvesting/b/blog/posts/a-very-compact-guide-to-energy-harvesting---part-034A Key Point This is a circuit can be used to support a 4x4 key matrix and be made energy efficient by not requiring perpetual polling. This is done by the use of interrupt inputs.When a key is pressed, the KBINT ISR (Interrupt Service Routine) is launen-USTelligent Community 12