completely rewrite the driver.

using one class to descripe two kinds of display.
add two displays used simultaneously example.
use : setTubeType() to select which type of display is going to be used.
add : add comment ,modify configuration files.

examples/combine_two_displays/combine_two_displays.ino

@@ -0,0 +1,51 @@
+#include <Wire.h>
+
+#include "grove_alphanumeric_display.h"
+
+Seeee_Digital_Tube tube1;
+Seeee_Digital_Tube tube2;
+
+/** 
+ * NOTICE:Every tubes display has the same default i2c address.
+ *        if you want to combine two(or more)display in one project,you should change the i2c
+ *           i2c address,by soldering the pad of display backside.
+ *        please refer to our wiki to get more details.
+ * */
+#define I2C_ADDR_AFTER_CHANGE_FOUR  0x75
+#define I2C_ADDR_DEFAULT_FOUR       0x71
+
+
+
+void setup()
+{
+    Wire.begin();
+
+    // If using four digital tubes, use this configuration.
+    tube1.setTubeType(TYPE_4,I2C_ADDR_AFTER_CHANGE_FOUR);
+
+    tube1.setBrightness(15);
+    tube1.setBlinkRate(BLINK_OFF);
+
+    // If using four digital tubes, use this configuration.
+    tube2.setTubeType(TYPE_4,I2C_ADDR_DEFAULT_FOUR);
+
+    tube2.setBrightness(15);
+    tube2.setBlinkRate(BLINK_OFF);
+
+}
+
+
+void loop()
+{
+    tube1.displayNum(1234);
+    delay(100);
+
+    tube2.displayNum(5678);
+    delay(100);
+
+    while(1);
+}
+
+
+
+