USB GPIO Alternate function

[cng]

Posted on March 26, 2013 at 01:59

I am using STM32L152 evaluation board. I realized that the USB HID module does not configure the USB D+ D- line as GPIO Alternate function. I wonder that what is the usage of GPIO Alternate function for USB?

[CMars.1]

STM32 products usually distinguish pin functions between "alternate" (require Alternate Function Register programming apart from peripheral configuration) and "additional" (peripheral configuration suffices).

STM32L152 probably has these pins as Additional and not Alternate. This can vary between different MCUs. Read each MCU datasheet for detailed information.