Strange Analog Output

I have been working on the VoltageReader example from the book
"Getting Started with the internet of things. I get it to build
and run but the output is kind of odd. It seems to cover about
90 percent of 1023 scale when left at one setting of the
potentiometer. Like the adc is just going up and down the scale
in a incremental manner. Anybody seen anything like that ?
The output is at the bottom.

Randy


using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;
using AnalogInput = SecretLabs.NETMF.Hardware.AnalogInput;

    public class VoltageReader
    {
        public static void Main()
        {
            // write your code here
            const double maxvoltage = 3.3;
            const double maxAdcValue = 1023;

            AnalogInput voltagePort = new AnalogInput(Pins.GPIO_PIN_A1);
            //var voltagePort = new AnalogInput(Cpu.AnalogChannel.ANALOG_1);      
            var lowPort = new OutputPort(Cpu.Pin.GPIO_Pin0, false);             
            var highPort = new OutputPort(Cpu.Pin.GPIO_Pin2, true);
            voltagePort.SetRange(0, 1023);
            
            double rawValue = voltagePort.Read();
            double value = 0;
            
            while (true)
            {
                Debug.Print(rawValue + " " + value.ToString("f"));
                Thread.Sleep(3000);
                rawValue = voltagePort.Read();
                value = ((double)rawValue * maxvoltage) / maxAdcValue;
            }
        }
    }




Here is the output.
9 0.03
28 0.09
42 0.14
57 0.18
128 0.41
515 1.66
964 3.11
958 3.09
927 2.99
674 2.17
362 1.17
131 0.42
26 0.08
118 0.38
37 0.12
26 0.08
22 0.07
26 0.08
54 0.17
24 0.08
26 0.08
27 0.09
26 0.08

Hi rseedle,

Which Netduino mainboard are you using? What version of firmware?

And...do you have anything plugged into the other analog pins? [If not...can you try connecting them all to GND really quickly to see if that affects your results?]

Welcome to the Netduino community,

Chris