add examples

examples/CustomRatio/CustomRatio.ino

@@ -0,0 +1,43 @@
+#include <Battery.h>
+
+Battery battery(7200, 8400, A0);
+/**
+ * 2 cells (2S1P) li-ion/li-poly battery wired to A0, continuous sensing
+ * https://github.com/rlogiacco/BatterySense#higher-than-5v-with-internal-voltage-regulator
+ *
+ *   +--------+
+ *   |        |
+ *   |       +-+
+ *   |       | | 33k
+ *   |       | |
+ * -----     +-+
+ *  ---       |---------+ A0
+ *   |       +-+
+ *   |       | |
+ *   |       | | 10k
+ *   |       +-+
+ *   |        |
+ *   +--------+---------+ GND
+ *
+ **/
+
+void setup() {
+	Serial.begin(9600);
+	while (!Serial);
+	float ratio = (33 + 10) / 10;
+	// 5V board, change to 3300 for a 3.3V board
+	battery.begin(5000, ratio);
+}
+
+void loop() {
+	digitalWrite(13, HIGH);
+	delay(500);
+	digitalWrite(13, LOW);
+	delay(500);
+
+	Serial.print("Battery voltage is ");
+	Serial.print(battery.voltage());
+	Serial.print("mV (");
+	Serial.print(battery.level());
+	Serial.println("%)");
+}