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Ganesh basawaraju
Visitor
Oct 30, 2026 6:22 AM UTC
Question

GPIO INITIAL STATE

i am using stm32F107 ,H563,F100RC ,in our application we using GPIO for relay operating with Opto couplers(pc817). when we program to fresh cpu , relay is getting on and same i re program the cpu same, repeating, may i now state behavior of GPIO .

3 replies

AScha.3
AScha.3
Super User
Oct 30, 2026 7:21 AM UTC

GPIO INITIAL STATE

is given in ds , as always.

see here as example: H5 , pin/ball definition

 

Pin name (function after reset) - is given in every ds for every cpu .

 

 + important: read the notes…. here from H563 :

 

+

On some cpu/SOC there are even functions, that are always active/working, even under reset !

  • Additional functions - here in H563 pin definition : the pins for usb PD , always active (pullup/down resistors...etc),

 

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    mƎALLEm
    mƎALLEm
    ST Technical Moderator
    Oct 30, 2026 8:23 AM UTC

    Hello ​@Ganesh basawaraju and welcome to the ST community,

    Are you seeing the same behavior on  stm32F107 + H563 + F100RC?

    What GPIO are you using for this purpose?

    To give better visibility on the answered topics, please click "Best answer" on the reply which solved your issue or answered your question.
    Andrew Neil
    Andrew Neil
    Super User
    Oct 30, 2026 8:47 AM UTC

    Welcome to the forum

    Please see How to write your question to maximize your chances to find a solution for best results.

     

    In particular, please post your schematic showing this relay.

    A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
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