Analog Inputs

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Unlike digital input pins which can only read high or low, analog pins can read a range of voltage levels. Micro-controllers based on 3.3V can read voltages anywhere between zero and 3.3V. In contrast to digital input pins that are 5V tolerant; the maximum applied voltage for analog input must not exceed 3.3V (for higher voltages a voltage divider or an op-amp circuit can be used).

Using a Light Sensor to Demonstrate Analog Input

This example uses a light sensor. Its output voltage varies with light intensity -- the darker the light the higher the voltage output. The following code requires the Microsoft.SPOT.Hardware assembly. Consult the Developers' Guide or the product manual for specific channels.

using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;


public class Program
{
    public static void Main()
    {
        AnalogInput lightSensor = new AnalogInput((Cpu.AnalogChannel)Cpu.AnalogChannel.ANALOG_7);
        double lightSensorReading = 0;

        while (true)
        {
            lightSensorReading = lightSensor.Read();
            Debug.Print(lightSensorReading.ToString());
            Thread.Sleep(500);
        }
    }
}