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Digital Input Pull-up/Pull-down Resitor


Best Answer ziggurat29, 01 May 2013 - 02:33 AM

depends on what you are doing.  but you should do one or the other:  either use builtin pullup/down, or use Port.ResistorMode.None and use external ones.

 

The ones activated by Port.ResistorMode are within the chip itself, and are nominally 50K, I believe, for the st32f4.  Whether that is useful to you or not depends on what you are doing specifically.  The feature is there as a convenience to circuit designers, to avoid having to populate a bunch of resistors on the board -- especially for things like buttons, etc.

 

EDIT:  hanzibal beat me to the post while I was composing, but I am so glad, because he stated that the resistors are applied 'infernally', which so often is true!

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#1 xmakina

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Posted 01 May 2013 - 01:40 AM

Hi,

 

I would like to clarify something with the Netduino. I bought a NDP2. I know you can change in code whether to use pull Port.ResistorMode.PullUp or Port.ResistorMode.PullDown. My question is, do I still have to add an external resistor component for the pull-up/pull-down or the board itself already provides the necessary resistors ? 

 

Thank you so much in advance.

 

xMakina



#2 hanzibal

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Posted 01 May 2013 - 02:17 AM

Hi! The microcontroller itself will apply the resistors infernally as you specify when defining the pin.

#3 ziggurat29

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Posted 01 May 2013 - 02:33 AM   Best Answer

depends on what you are doing.  but you should do one or the other:  either use builtin pullup/down, or use Port.ResistorMode.None and use external ones.

 

The ones activated by Port.ResistorMode are within the chip itself, and are nominally 50K, I believe, for the st32f4.  Whether that is useful to you or not depends on what you are doing specifically.  The feature is there as a convenience to circuit designers, to avoid having to populate a bunch of resistors on the board -- especially for things like buttons, etc.

 

EDIT:  hanzibal beat me to the post while I was composing, but I am so glad, because he stated that the resistors are applied 'infernally', which so often is true!



#4 xmakina

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Posted 01 May 2013 - 03:49 AM

Thank you so much to both of you hanzibal and ziggurat. actually, choosing between your posts as best answer if by far more difficult than doing the hands-on itself. haha But thank you so much for both your posts and I hope you still have more designers to enlighten,

 

cheers !



#5 hanzibal

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Posted 01 May 2013 - 08:48 AM

EDIT: hanzibal beat me to the post while I was composing, but I am so glad, because he stated that the resistors are applied 'infernally', which so often is true!

On this tiny tablet, the letters look the same plus I was in a hurry since I saw you were reading the post :-)

#6 ziggurat29

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Posted 01 May 2013 - 01:00 PM

can you see that when you are editing?  that someone else is also posting?  because that happens to me so so often, and it's mildly embarassing when it does.



#7 hanzibal

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Posted 02 May 2013 - 09:44 AM

I don't think you can see if someone else is posting but you can see who else is also reading the same post - it will show at the bottom left of the page. At this particular instance I actually didn't look but if I did and saw you reading I would assume you were about to answer  :)
 
In some other forums that I use, when hitting the then "Post" button in edit mode, if there have been new posts since you clicked the "Reply" button, you get a notification before your post is actually saved. This gives you a chance to modify or discard your reply post accordingly.
 
To my knowledge, this forums hasn't got that feature but it would be really nice to have.





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