update readme.md

Author: RobTillaart

CHANGELOG.md

@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.3.7] - 2022-11-16
+- fix #40 - add interrupt section to readme.md
+
 ## [0.3.6] - 2022-10-19
 - fix example PCF8574_rotaryEncoder.ino
 - add RP2040 to build-CI

PCF8574.cpp

@@ -2,7 +2,7 @@
 //    FILE: PCF8574.cpp
 //  AUTHOR: Rob Tillaart
 //    DATE: 02-febr-2013
-// VERSION: 0.3.6
+// VERSION: 0.3.7
 // PURPOSE: Arduino library for PCF8574 - 8 channel I2C IO expander
 //     URL: https://github.com/RobTillaart/PCF8574
 //          http://forum.arduino.cc/index.php?topic=184800

PCF8574.h

@@ -3,7 +3,7 @@
 //    FILE: PCF8574.h
 //  AUTHOR: Rob Tillaart
 //    DATE: 02-febr-2013
-// VERSION: 0.3.6
+// VERSION: 0.3.7
 // PURPOSE: Arduino library for PCF8574 - 8 channel I2C IO expander
 //     URL: https://github.com/RobTillaart/PCF8574
 //          http://forum.arduino.cc/index.php?topic=184800
@@ -14,7 +14,7 @@
 #include "Wire.h"
 
 
-#define PCF8574_LIB_VERSION         (F("0.3.6"))
+#define PCF8574_LIB_VERSION         (F("0.3.7"))
 
 #ifndef PCF8574_INITIAL_VALUE
 #define PCF8574_INITIAL_VALUE       0xFF

README.md

@@ -32,6 +32,17 @@ The library allows to read and write both single pins or 8 pins at once.
 Furthermore some additional functions are implemented that are playful and useful.
 
 
+#### Interrupts
+
+The PCF8574 has an interrupt output line (INT) to notice a MCU that one of the input lines has changed.
+This can be used to prevent active polling of the PCF8574, which can be more efficient.
+The library does not support this internally.
+
+There are two examples to show how interrupts can be used:
+- PCF8574_interrupt.ino
+- PCF8574_rotaryEncoder.ino
+
+
 ## I2C Clock
 
 Tested on UNO with **PCF8574_performance** showed that the PCF8574 still works at 500 KHz and failed at 600 KHz.

library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/PCF8574.git"
   },
-  "version": "0.3.6",
+  "version": "0.3.7",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=PCF8574
-version=0.3.6
+version=0.3.7
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for PCF8574 - 8 channel I2C IO expander