added ChangeI2cAddress example

-Also added a getAddress public function to access the private variable "_i2cAddr". I wanted this so I could print it directly in the example and verify the change.

examples/Example17-ChangeI2cAddress/Example17-ChangeI2cAddress.ino

@@ -0,0 +1,91 @@
+/*
+  SparkFun Electronics
+  SerLCD Library - Change I2C address
+  Pete Lewis - August 18, 2020
+
+  This example demonstrates how to change the i2c address on your LCD.
+  Note, once you change the address, then you will need to call ".begin()" again.
+
+  There is a set range of available addresses from 0x07 to 0x78, so make sure your
+  chosen address falls within this range.
+
+  The next thing to note is that when you change the address you'll
+  need to call .begin again to talk to that screen.
+
+  Finally if for some reason you've forgotten your new address. No big deal, run a
+  hardware reset on your screen to get it back to the default address (0x72).
+  To cause a hardware reset, simply tie the RX pin LOW, and they cycle power
+  (while continuing to hold RX low). Then release RX, and cycle power again.
+
+  The circuit:
+   SparkFun RGB OpenLCD Serial display connected through
+   a SparkFun Qwiic cable/adpater to an qwiic-enabled Arduino.
+
+  The Qwiic adapter should be attached to the display as follows:
+  Display	/ Qwiic Cable Color
+ 	GND	/	Black
+ 	RAW	/	Red
+ 	SDA	/	Blue
+ 	SCL	/	Yellow
+
+  Note: If you connect directly to a 5V Arduino instead, you *MUST* use
+  a level-shifter to convert the i2c voltage levels down to 3.3V for the display.
+
+  This code is based on the LiquidCrystal code originally by David A. Mellis
+  and the OpenLCD code by Nathan Seidle at SparkFun.
+
+  Also based off the original Arduino Library code with many contributions from
+  Gaston Williams - August 29, 2018
+
+  Some code/comments/ideas ported from the Qwiic Quad Relay Arduino Library
+  Written by Elias Santistevan, July 2019
+
+  License: This example code is in the public domain.
+
+  More info on Qwiic here: https://www.sparkfun.com/qwiic
+
+  AVR-Based Serial Enabled LCDs Hookup Guide
+  https://learn.sparkfun.com/tutorials/avr-based-serial-enabled-lcds-hookup-guide
+*/
+
+#include <Wire.h>
+
+#include <SerLCD.h> //Click here to get the library: http://librarymanager/All#SparkFun_SerLCD
+SerLCD lcd; // Initialize the library with default I2C address 0x72
+
+byte oldAddress = 0x72; // default 0x72
+byte newAddress = 0x71; // must be within 0x07 to 0x78, DEFAULT: 0x72
+
+void setup() {
+  Wire.begin();
+  Serial.begin(115200);
+
+  Serial.print("Connecting to SerLCD at 0x");
+  Serial.println(oldAddress, HEX);
+  lcd.begin(Wire, oldAddress); //Set up the LCD for I2C communication
+  Serial.println("Done\n\r");
+
+  lcd.setBacklight(255, 255, 255); //Set backlight to bright white
+  lcd.setContrast(5); //Set contrast. Lower to 0 for higher contrast.
+
+  lcd.clear(); //Clear the display - this moves the cursor to home position as well
+
+  // command to change address
+  // note this will also change class private variable "lcd._i2cAddr"
+  Serial.print("Changing address to 0x");
+  Serial.println(newAddress, HEX);
+  lcd.setAddress(newAddress);
+  Serial.println("Done\n\r");
+
+  Serial.print("Connecting to SerLCD at 0x");
+  Serial.println(newAddress, HEX);
+  lcd.begin(Wire); // note, new address argument is not needed. lcd._i2cAddr has been updated by ".setAddress()"
+  Serial.println("Done\n\r");
+
+  lcd.print("My new address: 0x"); // print it to the LCD for user victory experience
+  lcd.print(lcd.getAddress(), HEX); // note, we need to use public function to access private lcd._i2cAddr
+}
+
+void loop() {
+  // do nothing
+}

src/SerLCD.cpp

@@ -765,4 +765,14 @@ void SerLCD::setAddress(byte new_addr)
   _i2cAddr = new_addr;
 
   delay(50); //This may take awhile
-} //setContrast
+} //setAddress
+
+/*
+ * getAddress
+ * 
+ * Returns private variable I2C address
+ */
+byte SerLCD::getAddress()
+{
+  return _i2cAddr;
+} //getAddress

src/SerLCD.h

@@ -108,6 +108,7 @@ class SerLCD : public Print
 	void enableSplash();
 	void disableSplash();
 	void saveSplash();
+	byte getAddress();
 
   private:
 	TwoWire *_i2cPort = NULL;   //The generic connection to user's chosen I2C hardware