• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 98 subscribers
  • Views 277 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

GPIO Pulse Upon Wake-Up From System OFF Mode

Jared Hagel
Prodigy 70 points

Hello everyone,

Issue:

A long pulse (1 to 2ms) is seen after wakeup from device OFF mode. This pulse is seen on the pin corresponding to GPIO_126 = MMC1_DAT4. The line is programmed to maintain the line high by driving the line high as an output. This line is pulled strongly to ground using a 1k resistor. Because of this strong pull down the line is low even when programmed as an input with internal pull-up. Note that if we remove this pull down resistor from the line we do not see this issue. However removing this resistor is an expensive solution since we have many units deployed already.

Question:

What could be causing this 1-2ms low pulse? I thought the line should stay high across device OFF mode because the line is programmed as an output driving the line high. The OFF mode configuration is not used on this line. Could it be that this line acts as an input for 1-2ms after wakeup from device OFF mode? We have already implemented the workaround for the errata 'GPIO Drives Random Values When Device Comes Back from OFF Mode' by creating a WU dependency between WU domain and PER domain (PM_WKDEP_PER[4]: EN_WKUP=1).

Any insight appreciated!

Jared

  • 0
    TI__Guru 65405 points

    Hi Jared,

    You are right about: "the line will stay high across device OFF mode because the line is programmed as an output driving the line high. This line acts as an input for 1-2ms after wakeup from device OFF mode". You could use this workaround.

    BR

    Tsvetolin Shulev

  • 0 in reply to Cvetolin Shulev-XID
    Prodigy 70 points

    Hi Tsvetolin. Thanks for confirming my suspicion that the line acts as an input briefly after wakeup up from device OFF mode. However, I should have wrote that the workaround I described in my initial post did NOT work. Even with this workaround the line still acts as an input for 1-2ms after wake up. Therefore this line is always low for these 1-2ms. This line is connected to a reset pin on one of our components and is causing problems.

    Do you know of any way of ensuring that this line always acts as an output, even after wakeup from device OFF mode?

    Thanks again!

  • 0 in reply to Jared Hagel
    Prodigy 70 points

    Bump: is there a way prevent a GPIO from acting as an input after wakeup from device OFF mode?

    Thank you.