How to check UART baud rate without using BRR register?

[MMust.5]

Maybe in some register the baud rate is saved?

[Tesla DeLorean]

The hardware doesn't need it, it uses clock ratios.

​

Might find in a variable or structure held in Memory..

[MMust.5]

In what structure?

Where can I find the current UART baud rate in memory?

[Andrew Neil]

It's your software that configures the UART - including setting the baud rate - so your software must know what baud rate it set!

[Michal Dudka]

It is little bit strange request (your program writes some value into BRR, you should be able to find that value in your source code). But, simple, connect oscilloscope to UART TX signal, send some unambiguous character (like 0x00, or 0xFF etc.) and measure bit time duration from oscilloscope trace.

[Andrew Neil]

@Michal Dudka​ "It is little bit strange request (your program writes some value into BRR, you should be able to find that value in your source code)"

Absolutely!

"send some unambiguous character"

Best choice would be uppercase 'U' - that should give a square wave with 1 start & 1 stop bit ...

[Tesla DeLorean]

You do seem to struggle with very basic methods here.

https://community.st.com/s/question/0D53W00001db87nSAA/what-is-written-to-the-usartbrr-register

The machine uses relative clock ratios to relate one clockable source to another.

The machine doesn't keep a record of your "baud rate", it only knows that it is some fraction of the bus clock rate. ie Baud Rate = APBxCLK / USARTx->BRR

Will be in structure hUart,

ie hUart->Init.BaudRate where UART_HandleTypeDef *hUart;

[Tesla DeLorean]

If the RX pin is connected to a TIM Channel, you could measure the pulse widths, the shortest being One Bit Time, the others presumably being some higher integer multiple of that.

For example 9600 baud being around 0.1042666 ms