Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

pull pull down meaningon GPIO

yefj

Advanced Member level 4
Joined
Sep 12, 2019
Messages
111
Helped
0
Reputation
0
Reaction score
0
Trophy points
16
Activity points
809
Hello, In the photo bellow there is a diagram for general purpose input output(GPIO).
When they say in the manual "The following code configures pin 5 from Port C as a digital input with pull-up and filter"
We see in the diagram is just connecting the output to VDD and pull down is connecting the output to GND.
So if we have digital input of a square wave then the pull up cancels it totally because we have path to VDD (OR) ground.
We ruin our signal by doing pullup or pull down.
What is it good for?
Thanks

5.JPG


4.JPG
 

KlausST

Super Moderator
Staff member
Joined
Apr 17, 2014
Messages
17,458
Helped
3,941
Reputation
7,880
Reaction score
3,812
Trophy points
113
Activity points
115,742
Hi,

Explain "ruin". Best if you can calculate volts.

Klaus
 
  • Like
Reactions: yefj

    yefj

    points: 2
    Helpful Answer Positive Rating

betwixt

Super Moderator
Staff member
Joined
Jul 4, 2009
Messages
14,185
Helped
4,685
Reputation
9,385
Reaction score
4,439
Trophy points
1,393
Location
Aberdyfi, West Wales, UK
Activity points
121,142
You are not noticing the resistor symbols on the diagram.

The pull-up and pull-down are not direct connections to VDD or VSS, they enable a weak current source to maintain the pin in a known state when not being driven or having current drawn from it. The source is usually only a few uA so your external signal should easily drive against it. If in doubt, turn it off.

Brian.
 
  • Like
Reactions: yefj

    yefj

    points: 2
    Helpful Answer Positive Rating
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top