/*
 * Voltage divider with LDR 
 * 
 * Circuit:
 * 5V (Vcc) - LDR - R1 - GND
 * The node between LDR and R1 (V1, voltage drop across R1) is connected to analog input A0
 * R1 arbitrary, e.g. 10kOhms
 * 
 * The voltage V1 is converted to a digital number (dn) by means of an analog-to-digital converter (ADC).
 * The range of dn: 0 <= dn <= 1023 (10 bit resolution)
 * 
 * Conversion:
 * V1 = 0V -> dn = 0
 * V1 = 5V -> dn = 1023
 * 
 * Reconstruction of voltage from digital number:
 * V = dn / 1023 * 5V
 * 
 */

int AIN = A0; // Analog input pin number 

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("dn  V  mV");
}

void loop() {
  // put your main code here, to run repeatedly:
  
  int  dn = analogRead(AIN); // digital integer number between 0 and 1023 (10 bits, 2^10 different values)
  float V = (float)dn / 1024 * 5.0; // convert dn to float first, then divide by 1024
  int  mV = V*1000; // millivolts, converted from float
  
  Serial.print(dn);    // print to serial without a newline at the end, i.e. the next print is in the same line
  Serial.print("  ");  // spaces
  Serial.print(V);    
  Serial.print("  ");
  Serial.println(mV);  // last print with newline, i.e. the next print will be in the next line.
  
  delay(100); // pause in ms, 100 ms means 10 meas / sec.
}