Hi Nadia,
I hope you are doing well
Could you detail us your issues?
By the way ,are you using the USART SDK examples? Some of them implement UART blocking and others the UART non blocking functions (see ring buffer examples )
Diego
You might want to be a bit more specific, especially about the problems.
No reception, garbled messages, hardfault ?
Blocking function might cause problems. The transmission of a byte via takes a relatively long time, compared the the MCU's instruction speed.