UART communication between two Nucleo Board using DMA receive

[JAcksonPi]

I use two Nucleo-G0B1RE to communicate with each other using UART. UART5 of the master board is connected with UART1 of the slave board and both of the UARTs use DMA receive. When I first pressed the reset button of the slave board and then the master board, they could communicate successfully, but when I first pressed reset of master board and then slave board, the slave could transmit message but the master could NOT receive it. The only difference is the Power-on Sequence. what is the difference between UART detected another UART as soon as it is power on   and   UART detected after a short time.

[TDK]

If the receiver sees an invalid signal, it may enter an error state which you have to address before receiving more characters. Resetting mid-way is likely to push out an invalid signal on the UART TX line.

[FBL]

Hello @JAcksonPi 

Could you explain "both of the UARTs use DMA receive"? Could you share your UARTs configuration and DMA initiation?

[JAcksonPi]

UART5 of master is connected with UART1 of salve. I used exactly the same program for both MCUs. Maybe I should add some statement to continuously detect if slave exists in master code?

[JAcksonPi]

When master is initialized first, it could transmit correct message to slave and salve could send correct message (as least in txBuf) ，however master cannot receive this response. Maybe I should continously detect slave in while loop of  master code.