MSP430's port-interrupt-request logic helps debounce contacts

摘要

Contact debouncing requires monitoring an input and waiting for it to stop toggling or at least establish that it's definitely switching from its initial state. You can use either analog or digital filtering plus hysteresis to accomplish contact debouncing, but this approach uses a lot of resources, including parts, board space, and CPU time, when multiple inputs need to be conditioned. Alternatively, you can either detect just the first state change or sample the input at least twice as often as the contacts can bounce. Sampling at mechanical vibration frequencies must be avoided. Both methods also require time delays to ensure that the contacts have finished bouncing.