This is an Arduino library that enables you to read a Keypad using interrupts. The difference with Keypad.zip (from Mark Stanley and Alexander Brevig) is that may pass any time between successive call to getKey() without losing any key. In Keypad.zip lib the function getKey() must be called continuously with a minimum delay between consecutive calls, otherwise keys can be lost. With the KeypadInt library the function getKey() does not need to be called continuously. Keypad lib as of version 3.0 supports multiple key presses while KeypadInt lib only supports a single key.
KeypadInt lib uses a buffer of up to 10 keys that are stored in case the CPU is occupied in other tasks.
KeypadInt example is based on example of Keypad.zip library (from Mark Stanley and Alexander Brevig) but the implementation of the library is different as is based in interrupts instead of polling.
KeypadInt lib uses overflow interrupt of timer2 (2.048mS) but does not modify the configuration of the timer2, so does not affect the AnalogWrite() function (pins ~3 and ~11 on Arduino Uno) that maintains a PWM with a frequency of 488,28Hz.
KeypadInt lib spends 160us every 51mS (0.3% of CPU) and does not interfere with Timer0 interrupt that controls the functions millis(), micros() and delay().
As an example of a typical Keypad tested, the time of a momentary key pressed varies between a minimum of about 190ms and a maximum of 380ms and the key pressed has no rebounds. Obviously the maximum time can be increased if the key is pressed continously.
To obtain the most recent version of the code or to report issues (or, better, provide fixes), please visit the Github pages at
https://github.com/toranlo/KeypadInterrupt.
Inquiries via the Github issue tracker, please. This way, others may benefit from the answers.
(C) 2022 toranlo
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.