PA1 pin reconfig to input-mode causes "lost connection"

Hello, I try init PA1 to input mode as ecternal interrupt pin.
Then I initialize it as:

stm32_gpiosetevent(GPIO_RPM_2, true, false, true,(xcpt_t)_rpm_irq_2,NULL);

When I do it, plate falls to disconnection. My connection works through USB with QGround. I think that something important is defined at this pin. And when I reconfigure it, board falls away. (QGround says - COMMUNICATION LOST)
I commented all modules, but problem still exist. I still cannot find, why PA1 calls troubles. Other pins (ex PA2) dont causes this problem.
What thing can be wrong in it?