GPIO Pull Up during reset.

franmoya · ‎2013-02-20

Posted on February 20, 2013 at 12:38

Hi everyone!

I connected one STM32F103 GPIO pin configured as OutputPP to -> a STM32F0 GPIO pin configured as Input Floating with EXTI.

While STM32F103 hardware reset, the line is pulled down, so the STM32F0 EXTI is triggered (low edge). This behaviour is unwanted in my procedure.

In the STM32F103 reference manual says: ''During and just after reset, the alternate functions are not active and the I/O ports are configured in Input Floating mode''

How can I pull up the line even during reset? I tried forcing it with an external strong pull up but it doesn't work.

I know I could use a buffer, but right now it is not a possibility.

Thanks in advance.

Best regards,

FM

emalund · ‎2013-02-20

Posted on February 20, 2013 at 14:06

sounds like a pulse generated during port init

put a scope on and step therough the port init

I would as a first try

1)start clock

2)set pin high

3)config push-pull

I imagine reversing 2 and 3 will generate your problem

franmoya · ‎2013-02-22

Posted on February 22, 2013 at 12:04

Thanks Erik, that was the problem indeed!

:)