[Answered] Meaning of GPIO_PULLUP_PULLDOWN

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kolban
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[Answered] Meaning of GPIO_PULLUP_PULLDOWN

Postby kolban » Wed Nov 02, 2016 5:32 am

Looking at the GPIO API I see a function called gpio_set_pull_mode(). I'm wondering how to describe this function. For input, I can imagine no signal (floating input) being treated as high with "pull up" and low with "pull down". What then does the option GPIO_PULLUP_PULLDOWN mean?

Does this function have any semantics for GPIO pins flagged as "output"?
Last edited by kolban on Wed Dec 28, 2016 10:56 pm, edited 1 time in total.
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kolban
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Location: Texas, USA

Re: Meaning of GPIO_PULLUP_PULLDOWN

Postby kolban » Wed Dec 28, 2016 1:46 am

*bump*
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ESP_Angus
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Re: Meaning of GPIO_PULLUP_PULLDOWN

Postby ESP_Angus » Wed Dec 28, 2016 9:53 pm

This took me a moment to understand as well, had to check with coworkers. Setting GPIO_PULLUP_PULLDOWN turns on both pull-up and pull-down resistors, which pulls the pin voltage to approximately VCC/2.

Not useful for digital GPIO functions, but you can use this to bias the input when sampling an analog signal.

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