add examples

examples/RGBBatteryIndicator/RGBBatteryIndicator.ino

@@ -0,0 +1,58 @@
+#include <Battery.h>
+
+// 9V alkaline battery
+Battery battery(5000, 9000, A0);
+
+#define RED 5
+#define GREEN 6
+#define BLUE 7
+
+void setup() {
+	Serial.begin(9600);
+	while (!Serial);
+	battery.begin(5000, 2.0, &sigmoidal);
+    pinMode(RED, OUTPUT);
+    pinMode(GREEN, OUTPUT);
+    pinMode(BLUE, OUTPUT);
+}
+long ms = 0;
+bool on = true;
+
+void loop() {
+    long v = battery.voltage();
+    if (battery.level(v) >= 75) {
+        // blue: everything is fine
+        digitalWrite(RED, LOW);
+        digitalWrite(GREEN, LOW);
+        digitalWrite(BLUE, HIGH);
+    } else if (battery.level(v) >= 50) {
+        // green: battery is ok, but not full
+        digitalWrite(RED, LOW);
+        digitalWrite(GREEN, HIGH);
+        digitalWrite(BLUE, LOW);
+    } else if (battery.level(v) >= 20) {
+        // yellow: battery is getting low
+        digitalWrite(RED, HIGH);
+        digitalWrite(GREEN, HIGH);
+        digitalWrite(BLUE, LOW);
+    } else if (battery.level(v) >= 5) {
+        // red: time to change the battery
+        digitalWrite(RED, HIGH);
+        digitalWrite(GREEN, LOW);
+        digitalWrite(BLUE, LOW);
+    } else {
+        // blinking red: level is critical
+        digitalWrite(RED, on);
+        digitalWrite(GREEN, LOW);
+        digitalWrite(BLUE, LOW);
+    }
+    if (millis() - ms > 250) {
+        Serial.print("Battery voltage is ");
+        Serial.print(v);
+        Serial.print(" (");
+        Serial.print(battery.level(v));
+        Serial.println("%)");
+        ms = millis();
+        on = !on;
+    }
+}