problem using OTG_FS_VBUS pin like gpio output

jagracia · ‎2014-07-16

Posted on July 16, 2014 at 09:57

Hi,

I�m using pin A9(OTG_FS_VBUS) like GPIO and I have configured it like output. The problem is that when cpu boots it sets pin to high level, after cpu executes my gpio init routine and the pin works well and I set it to low level. The problem is gpio attach a relay and when cpu starts the init pulse produces a non desiderable conmutation. I think the problem is the alternate function of the pin for usb, but I don't know how can I deactivate it to avoid the init high pulse. I have tried to pull down externally and left it floating too, but in both cases the pins goes high at start.The cpu boot from flash memory(BOOT1 =X, BOOT0 = 0) and the cpu is a STM32F205RF.

Thanks.

#usb-pin-vbus #usb-otg-fs #stm32

Amel NASRI · ‎2014-08-06

Posted on August 06, 2014 at 12:42

Hi,

Don't think there is an activated alternate function but may be there is a pull-up for this pin. Check your schematic.

-Mayla-

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