4 replies to this topic

[kenNET]

I'm struggling with external buttons, the event fire several times when pressing the button. I need some advise on how to wire it up and values for the resistor (I use 10k now). If I use ONBOARD_SW1 then all works just fine. See picture how I wire it up now.

_btn1 = new InterruptPort(Pins.GPIO_PIN_D6, true, Port.ResistorMode.PullUp, Port.InterruptMode.InterruptEdgeLow);
_btn1.OnInterrupt += new NativeEventHandler(_btn1_OnInterrupt);

static void _btn1_OnInterrupt(uint data1, uint data2, System.DateTime time)
{
   _numClicks++;

   if (_numClicks> 10)
      _numClicks= 1;

   //code for LCD show "_numClicks"
}

Attached Files

•  buttons.PNG   67.1KB   115 downloads

[Jim Davies]

Hi Ken,

You're probably seeing contact bounce on your buttons. You can either debounce in software or add a small capacitor from each digital input to ground, to 'smooth' the signal a bit. Also, have you tried the 3.3V instead of the 5V - might make a difference?

See for example:

Interrupting

Also try searching for 'glitch' or 'bounce' in the Forums search box.

Jim

[Fred]

Try this to ignore any button presses within 200ms.

const int DEBOUNCE_TIME = 200;
DateTime _lastButtonPress = DateTime.Now;

_btn1 = new InterruptPort(Pins.GPIO_PIN_D6, true, Port.ResistorMode.PullUp, Port.InterruptMode.InterruptEdgeLow);
_btn1.OnInterrupt += new NativeEventHandler(_btn1_OnInterrupt);

static void _btn1_OnInterrupt(uint data1, uint data2, System.DateTime time)
{
    // Debounce - ignore multiple presses within 200ms
    if (time < _lastButtonPress.AddMilliseconds(DEBOUNCE_TIME)) return;
    _lastButtonPress = time;

   _numClicks++;
   if (_numClicks> 10)
      _numClicks= 1;

   //code for LCD show "_numClicks"

}

[Driver A]

Why not play with the Cpu.GlitchFilterTime instead? I think it's meant to be used for handling bounces.

I've noticed it is set to 0 by default so I'm not sure what an InterruptPort with "glitchFilter = true" does.

// set glitch filter to 1 second
Cpu.GlitchFilterTime.Add(new TimeSpan(TimeSpan.TicksPerSecond));

[Chris Walker]

Why not play with the Cpu.GlitchFilterTime instead? I think it's meant to be used for handling bounces.

The .NET Micro Framework handles glitch filtering different ways on different on microcontrollers.

On some of the microcontrollers, it uses a timespan (Cpu.GlitchFilterTime) to filter out glitches over a set time period.

On others (like the AT91SAM7X used on Netduino), it polls the input a few times to get a consistent reading instead.

I don't know of any reason that the SAM7X microcontroller couldn't support Cpu.GlitchFilterTime though...if you wanted to tweak the source to support it you could do so.

Chris