There are two approaches to this - either or both might be needed. 1) Use external stiff pull-up resistors on the keyboard lines that=20 are normally low. This reduces the input impedance and thus=20 sensitivity to external electric fields. 2) Improve the keyboard debounce so that a phantom trigger=20 (Interrupt) does NOT register a key-press. The unit would wake up,=20 see that there is no key pressed, then go back to sleep. dwayne At 02:25 PM 3/21/2017, John Hansen wrote: >I'm doing a project that involves a keyboard scan. The project is battery >operated with the usual matrix structure with the keypad rows set as input= s >and the columns set as outputs. The inputs have the internal pullups >enabled and I'm using the wakeup on change interrupt. It works >perfectly (with very little current draw as expected) except for one >thing. If I bring my hand close to the keypad while it is asleep, it wake= s >up and registers a keypress. > >This project is designed to be plugged into a radio and when it is plugged >in (that is the keypad ground is connected to the radio ground), these >phantom keystrokes go away. > >Is there any way to get this behavior to stop when the keypad is not >plugged in? > >Thanks for any advice. > >John --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA 780-489-3199 voice 780-487-6397 fax 888-489-3199 Toll Free www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .