Merge pull request adafruit#199 from flywire/master

#define SCREEN_ADDRESS instead of hard-coded value

Author: ladyada

examples/ssd1306_128x32_i2c/ssd1306_128x32_i2c.ino

@@ -32,6 +32,7 @@
 // On an arduino MEGA 2560: 20(SDA), 21(SCL)
 // On an arduino LEONARDO:   2(SDA),  3(SCL), ...
 #define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
+#define SCREEN_ADDRESS 0x3C ///< See datasheet for Address; 0x3D for 128x64, 0x3C for 128x32
 Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
 
 #define NUMFLAKES     10 // Number of snowflakes in the animation example
@@ -60,7 +61,7 @@ void setup() {
   Serial.begin(9600);
 
   // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
-  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3C for 128x32
+  if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
     Serial.println(F("SSD1306 allocation failed"));
     for(;;); // Don't proceed, loop forever
   }

examples/ssd1306_128x64_i2c/ssd1306_128x64_i2c.ino

@@ -27,7 +27,12 @@
 #define SCREEN_HEIGHT 64 // OLED display height, in pixels
 
 // Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
+// The pins for I2C are defined by the Wire-library. 
+// On an arduino UNO:       A4(SDA), A5(SCL)
+// On an arduino MEGA 2560: 20(SDA), 21(SCL)
+// On an arduino LEONARDO:   2(SDA),  3(SCL), ...
 #define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
+#define SCREEN_ADDRESS 0x3D ///< See datasheet for Address; 0x3D for 128x64, 0x3C for 128x32
 Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
 
 #define NUMFLAKES     10 // Number of snowflakes in the animation example
@@ -56,7 +61,7 @@ void setup() {
   Serial.begin(9600);
 
   // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
-  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3D)) { // Address 0x3D for 128x64
+  if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
     Serial.println(F("SSD1306 allocation failed"));
     for(;;); // Don't proceed, loop forever
   }