pull pull down meaningon GPIO

Status
Not open for further replies.
Y

yefj

Advanced Member level 4
Joined
Sep 12, 2019
Messages
1,199
Helped
1
Reputation
2
Reaction score
3
Trophy points
38
Activity points
7,237
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




 

Hi,

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

Klaus
 
Reactions: yefj

    Y

    yefj

    Points: 2
    Helpful Answer Positive Rating
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.
 
Reactions: yefj

    Y

    yefj

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…