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arduino_keypads

This repository contains several separate arduino format libraries, each one adding to the library Keypad external expansion port communication via an I2C (or Wire( )) port on the arduino microprocessor.

The separate libraries each handle the I/O needed by Keypad for different expansion port chips:

  • Keypad_I2C - PCF8574, PCF8574A and PCF8575
  • Keypad_I2Ca - PCA9554, PCA9555, PCA9534, PCA9535, PCA9539, PCA6408, PCA6416
  • Keypad_MC16 - MCP23016
  • Keypad_MCP - MCP23008
  • Keypad_MC17 - MCP23017
  • Keypad_tw - PCF8574, PCF8575 using the TinyWire lib on atTiny processors

The reason for separate libraries for each sort of expansion port IC is that their register sets, while implementing similar I/O functions, are generally not compatible among the devices, or/and because the I/O needed for Keypad is a small subset of the port chip capabilities, a system will likely only contain one type of port IC so a simple program library for that specific device will have a smaller memory footprint than would a single larger program that could handle all devices.

To use the libraries, download the .zip file, unzip to a temporary location, and then move the library desired into your libraries folder. The library manager does not work on the entire repository.

A recent update to the libraries permits the optional specifation of an I2C port as an alternative or in addition to Wire on those arduino that have more than one I2C bus. See the example Hello_I2Cboth in Keypad_I2C for using two expansion port chips on MKR ZERO. See also the arduino tutorial Adding more Serial Interfaces to SAMD microcontrollers (SERCOM)

The Keypad library is found on github.

An interesting use of Keypad's features enables decoding of quadrature encoders--see the examples KeypadEnc, and KeypadEnc_I2C in the Keypad_I2C library.

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arduino libraries for keypad interface on I2C bus

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