GPIO configuration primer under STM32CubeMX

[mkbrown32]

Posted on August 22, 2015 at 04:11

Is there a document that describes the selection of push pull, open drain,

maximum output speed, AHB clock, etc   for GPIO port operation  on STM32F427xx under STM32CubeMX ? The datasheets for the chips on the PCB to which  the GPIO pins are connected do not state explicitly a requirement of one or the other of these  PIO configuration selections. I am not seeing any output, though the RCC clock is activation and another port is inputting successfully. #gpio-output-drain-push-pull

[Nesrine M_O]

Posted on August 22, 2015 at 13:06

Hi  Aeneas,

I'd highly recommend you to refer to this

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/user_manual/DM00104712.pdf

 about STM32CubeMX for STM32 configuration and initialization C code generation.In the paragraph “GPIO Configuration windowâ€�, you find how to configure the settings of the GPIO pins.-Syrine-

[mkbrown32]

Posted on August 22, 2015 at 23:25

That document section referenced does not describe what the STM32

circuitry is doing differently under each choice and under which circumstances, connected to what sorts of devices, each choice of GPIO configuration it presents should be selected.

[Tesla DeLorean]

Posted on August 23, 2015 at 05:52

Push-Pull and Open-Drain are concepts beyond the STM32, you'd pick the appropriate one for the interface/device you're attaching them too.

The ''speed'' is a bit different, it actually relates the slew-rate of the pin, ie how aggressively the pin is driven high/low. It's going to depend on what exactly you're driving the signal into, and the load it presents. A serial point is only going to need a 1 or 2 MHz setting.

[Rosiney Silva]

Posted on August 23, 2015 at 21:58

A

bout

push-pull

and

open drain

:

http://coactionos.com/embedded%20design%20tips/2013/10/21/Tips-Understanding-Microcontroller-Pin-Input-Output-Modes/

[mkbrown32]

Posted on August 25, 2015 at 23:25

After experimenting with the different GPIO configuration options, I did not notice

much difference in output voltage measurements. In all cases, I am seeing all of my data pins transition between 3.3V and maybe 3V, instead of 3.3V to Ground,  (if they show  transition at all). The span of high to low voltages is contrained by some sort of electrical issue, whether it is configuration of the STM32 chip or from outside, is still unclear.