why using SWDIO_IN_PIN and SWDIO_OUT_PIN for STM32F103

[sdyncyang]

Hi
I am confusing on using SWDIO_IN_PIN and SWDIO_OUT_PIN two pins with 100ohm for STM32F103CB, and find the signal is always keeps high, the DAP connect in keil is failed ...could some one give the help on this issue ? thanks

[mathias-arm]

The point of having separate SWDIO_IN_PIN and SWDIO_OUT_PIN pins is to avoid reconfiguring the GPIO pin from output to input in the middle of the SWD transactions. If I remember correctly SWDIO should be high most of time. Do you see SWCLK changing but SWDIO never does?