# ARM: Read the value of an Alternate Function pin

I have an ARM STM32 where each GPIO pin can be configured as "input", "output", "analogue" or "alternate function". In "alternate function" mode, the ARM drives a lot of the logic for basic communication protocols, removing some of the grunt work for the programmer.

While I have been able to "read" the value of input and output GPIO pins using the standard library functions GPIO_ReadInputDataBit and GPIO_ReadOutputDataBit, I cannot seem to be able to read the value of alternate function pins without using a scope.

Is there a way to query the ARM about the value of its alternate function pins?

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