Arduino Library to approach PCA9555 I2C expander with digitalRead, digitalWrite, pinMode and functions. Implemented begin() to check connection with PCA9555 and optional interrupt functionality.

##Installation:

• a) Just download the zip file
• b) move PCA9555_LIB to the Users Arduino library (usually My documents\Arduino\Libraries)
• c) Create a new sketch and copy the example file into your sketch
• d) Compile, download and done.

• pinMode() same as standard Arduino
• digitalRead() same as Arduino
• digitalWrite() same as Arduino
• begin() checks if PCA9555 is responsive
• pinStates() ISR retrieves state of all I/O pins
• stateOfPin() returns the state of a particular pin
• setClock() sets clock speed

The code supports either pinnumbers 0 - 15 or ED0 - ED15. This to stay more or less in sync with Arduino. alertISR() is used to point to the actual ISR for the use of attachInterrupt() from Arduino.