3 replies to this topic

[Flores]

I would be cool if the was a way to create a sort analog interrupt port. With a trashhold for a parameter.. if it changes more than the trashhold it will create an interrupt. Is this a good idea for future firmware? Or is this technically impossible?

[Chris Walker]

That could definitely be done, although it would be easiest in managed code...and it would have limits as to how often the measurements happened. GPIOs can drive interrupts at a low level, but analog inputs are measured on request (with setup time, measurement time, etc.). You could create a class which checked the value every ###ms using a timer...and then fired an event when the value passed the threshold. This would be great for room temperature sensors (perhaps check every ten seconds) and even to a limited extent for things like volume knobs (check every 50ms-100ms perhaps). Chris

[ajcg1973]

I just wrote a class to do just that. I hope that it is helpful...

using System;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;

namespace AJB
{
 public delegate void AnalogEventHandler();

 class AjbAnalogInterupt
 {
  public event NativeEventHandler AnalogInterrupt;

  private const double SINGLE_ANALOG_VALUE = 0.00322265625;

  private ExtendedTimer _timer;
  private AnalogInput _an1;
  private int _analogHigh;
  private int _analogLow;
  private int _timerDelay;
  private InterruptCause _interruptCause;
  private int _readAnalogValue = 0;

  public enum InterruptCause
  {
   InterruptOnVoltageHighOrLow,
   InterruptOnVoltageHigh,
   InterruptOnVoltageLow,
   InterruptOnVoltageRead
  }

  public int CurrentAnalogValue
  {
   get { return _readAnalogValue; }
  }

  public double ConvertAnalogValueToVoltage(int anVal)
  {
   if (anVal > 0)
    return (SINGLE_ANALOG_VALUE * anVal);
   else
    return 0;
  }

  public AjbAnalogInterupt(Cpu.Pin anPin, int CheckAnalogMsInterval, InterruptCause interruptCause, int AnalogHighValue, int AnalogLowValue)
  {
   _timerDelay = CheckAnalogMsInterval;
   _interruptCause = interruptCause;
   _analogHigh = AnalogHighValue;
   _analogLow = AnalogLowValue;
   _timer = new ExtendedTimer(new System.Threading.TimerCallback(CheckAnalog), null, _timerDelay, _timerDelay);
   _an1 = new AnalogInput(anPin);
  }

  private void CheckAnalog(object o)
  {
   _readAnalogValue = _an1.Read();

   switch (_interruptCause)
   {
    case InterruptCause.InterruptOnVoltageHigh:
     if (_readAnalogValue > _analogHigh)
      AnalogInterrupt(new uint(), new uint(), new DateTime());
     break;
    case InterruptCause.InterruptOnVoltageLow:
     if (_readAnalogValue < _analogLow)
      AnalogInterrupt(new uint(), new uint(), new DateTime());
     break;
    case InterruptCause.InterruptOnVoltageHighOrLow:
     if ((_readAnalogValue > _analogHigh) || (_readAnalogValue < _analogLow))
      AnalogInterrupt(new uint(), new uint(), new DateTime());
     break;
    case InterruptCause.InterruptOnVoltageRead:
     AnalogInterrupt(new uint(), new uint(), new DateTime());
     break;
   }
  }
 }
}

To use:

using System;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;

using AJB;

namespace NetduinoApplication1
{
 public class Program
 {
  static AjbAnalogInterupt anInt;

  public static void Main()
  {
   anInt = new AjbAnalogInterupt(Pins.GPIO_PIN_A0, 1000, AjbAnalogInterupt.InterruptCause.InterruptOnVoltageHighOrLow, 300, 30);      
   anInt.AnalogInterrupt += new AJB.NativeEventHandler(anInt_AnalogInterrupt);

   while (true) {}
  }

  static void anInt_AnalogInterrupt(uint data1, uint data2, DateTime time)
  {
   Debug.Print("Returned voltage: " + anInt.ConvertAnalogValueToVoltage(anInt.CurrentAnalogValue).ToString("N4") + " volts - Raw value: " + anInt.CurrentAnalogValue.ToString());
  }
 }
}

Let me know if you need help...

[Flores]

Gonna try this, thanks.