Testing some code to read the voltage divider and convert the A/D read to a voltage.

The 4.092  will need to be adjusted based on your resistors and tolerances.

This pix shows the web board, but the sample code is just testing the voltage divider.. I found the w5100 introduces  resistance on pin A2,3,4,5 requiring some code tweeks. Also A0/A1 are not usable  without modes the the network module since those pins are used for SD card control. 

/*

Read voltage divider module.

Gary Sanders (N8EMR)

ohgary@gmail.com

*/

int volt_pin=5;

void setup() {

Serial.begin(9600); // initialize serial communications for debugging.

}

void loop() {

float voltage;

float l_volt;

l_volt=analogRead(volt_pin);

voltage=(l_volt/4.092)/10;

Serial.print(voltage);

Serial.println("V ");

delay(1000);

}