3 replies to this topic

[sjmill01]

I have used these lines of code successfully for PWM:

 

inputPort13 = new InterruptPort(Pins.GPIO_PIN_D13, true, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
            inputPort13.OnInterrupt += new NativeEventHandler(inputPort_OnInterrupt13);

For ResistorMode, if I use "Pulldown" or "PullUp" instead, are the resistors built in to the Netduino or would I make an external circuit on my signal wire?

 

Also, is there a preferred resistormode to use?

 

Thanks,

Sean

[Nevyn]

I don't think there is a preferred mode, it really depends upon what you are doing.

 

Take a simple switch circuit where closing the switch pulls the output high.  In this case I would be detecting say the transition from low to high, so rising edge.  In order to prevent the line from floating from ground when the switch is open I would use a pull down resistor.

 

In the reverse case where the switch pulls the line to ground I would be detecting falling edge and using a pull up resistor.

 

In both of these cases the resistor stops the line being in an undefined state, i.e. floating.

 

If the pin on the microcontroller was connected to another IC where the output was always either one of low or high then you may not need a resistor at all.

 

Hope this helps,

Mark

[Razvan]

Another question on the same subject is: When you choose PullUp value (for example) does this activate an internal pull up resistor or you're simply telling the processor 'hey I have connected a resistor between the pin and the Vcc' ?

[Nevyn]

Should be internal pull up.

Regards,
Mark