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State of UART pins during a reset on STM32F439

LKish.1
Associate

I am having a hard time finding out the state of the UART pins while the chip is held in RESET. Are pins E2, D5, D4, and E1 held in a high-impedance state while the RESET pin H9 is pulled low? I suspect they are, but am trying to confirm through documentation.

Thank you.

1 ACCEPTED SOLUTION

Accepted Solutions
TDK
Guru

This information is in the reference manual. Look at the GPIOx register settings.

Most pins are set to high impedance input mode with no pull with a few exceptions for pins used for programming.

0693W00000ANJq2QAH.png

If you feel a post has answered your question, please click "Accept as Solution".

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3 REPLIES 3
Ozone
Lead

They are not "UART pins" during/after reset.

One of the side effects of a reset is to revert periperhal registers to their default (reset) value.

Check the GPIO peripheral register documentation, and those of the involved system config registers.

Pin goes back to their main function upon reset. Later on, it depends on the contents of the RTC registers even after reset because these registers are not reset by the main reset. My question is more towards voltage values of these pins during reset. Are they pulled to ground, vcc or floats?

TDK
Guru

This information is in the reference manual. Look at the GPIOx register settings.

Most pins are set to high impedance input mode with no pull with a few exceptions for pins used for programming.

0693W00000ANJq2QAH.png

If you feel a post has answered your question, please click "Accept as Solution".