STM32F4 USART problem

I’m trying to establish communication with my board via USART and have problem.

If board send anything to me, I can see it just fine.
But when I send anything to board, board read first character (or multiple individual chars with delay) normally, but everything else is trashed (same way for the same data)

I send:
41 41 41 41 41 41 41 41

Board receive
41 50 05 41 50 05 50 5d 15 95 41 75 15 95

If something is misconfigured, why I receive data from board without any problems?

You are only reading the first character.

I read it using driver, and it’s done in loop.
If I send each char with delay they are read by board correctly.
But if I send them right away, then only 1st is read correctly.

that almost sounds like a bit-count issue. I’d try altering parity and stop bit settings, and see if that changes the behavior (not saying it’ll fix it, just to give you a better view of the actual data you get).