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Correct GPIO Configuration of CAN RX Pin

Question asked by kjaergaard.lars on Sep 8, 2014
Latest reply on Sep 9, 2014 by kjaergaard.lars

In all examples I can find (ST Std driver library, STM32CubeF4, STM32CubeMX...) the CAN RX Pin is always configured regarding GPIO as Alternate Push/Pull Pin (Output) like the CAN TX Pin. I would expect the CAN RX pin to be configured as an input Pin regarding the GPIO setup - can anyone explain this? I don't want to shortcircuit the transceiver/microcontroller when attaching the Microcontroller's CAN RX pin to the transceivers RX Pin - the transceiver must drive the pin while the microcontroller's CAN rx pin must have high impedance (Input).

Does the microcontroller internally disable the Push/Pull gates as the CAN is enabled for a Pin or what is the logic in having to configure an Input pin as Alternate Push/Pull in order to get it to work? The microcontroller in question is the STM32F429.