Debugging odd push button behavior

Status
Not open for further replies.
M

monteie

Newbie level 4
Joined
Jun 16, 2009
Messages
7
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,350
I have the following circuit, and I noticed something I've never seen before on my scope when I release the button. I have attached the schematic and the waveform. The button is IC has an internal pullup to 1.8V.

As you can see, when I release the button, the voltage rises to about mid level for a few microseconds and then proceeds to rise to 1.8v. At first I though it was mechanical bounce in the switch, but that theory wasn't consistent with what I've seen before. Anyone have any idea would could be going on here?

 

Attachments

  • wierdrisingedge.png
    20.4 KB · Views: 121

Hi,

* to "what" IC?
* where is the pullup?
* is it a simple mechanical pushbutton?
* where did you measure the signal?

Klaus
 

The IC is SPEAr300 from ST

Pullup is configured in the IO. I also assume there is ESD clamping inside

It's a small mechanical push button on a flex. Off-mom

Measured the signal at the IC


Thanks!
Eric
 

Can you disconnect the IC and test the signal? Where the other end of the switch going? Connect that to the Vcc, if possible. I cannot see the charging/ discharging of the capacitor.
 

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…