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MSP430G2312: I/O Port Question

Part Number: MSP430G2312

Hi Team,

Posting for our customer. When the port is set to I/O input and internal pull-up and pull-down resistors are enabled, how much current does the port sink and source due to contact on/off when the mechanical contact switch is directly connected from the outside?

Also, with the same specifications, what would be the appropriate value of the filter capacitor for chattering countermeasures?

Thanks in advance!


Kind Regards,

Jejomar

  • Pullups are done with internal 35k resistors , that might be 20 to 50k, PDF clearly says that. So divide Vcc by that value, and that state will be for button being pressed. If not pressed then it will not take any current.

    For de-bouncing use appropriate delay like 30-40ms depending on physical button type, |'ve never used capacitors for that unless someone has badly programmed button detection and source code was unavailable :)

  • Jejomar,

    What Adam indicated is the right direction to think about for your questions. 

    If you do want to do some de-bounce via HW, then you would need to do some type of low-pass filter on the line. Values of components would depend on what cutoff frequency you want to do.

    That being said, a SW solution via a timer to do button de-bounce maybe preferred, as Adam indicated, as it can be tuned easier, and its cheaper from a component and layout perspective.  

  • 私は参照していただきありがとうございます

  • 私は参照していただきありがとうございます