Can a UART port change baud rate at runtime?

Question

I've been probing this CCTV DVR board trying to find a serial port to see if I can get console access to it. I found a set of 4 through holes with no headers that looked like a good candidate. I hooked up to my Bus Pirate in UART mode at a baud rate of 115200 and it seemed promising at first:

System startup

U-Boot 2010.06 (Dec 27 2018 - 17:06:41)

Check Flash Memory Controller v100 ... Found
SPI Nor(cs 0) ID: 0xc2 0x20 0x18
Block:64KB Chip:16MB Name:"MX25L128XX"
SPI Nor total size: 16MB
*** Warning - bad CRC, using default environment

In:    serial
Out:   serial
Err:   serial

Then things get weird. The next line has legible text but some garbage in it, then after that nothing but garbage:

�P���Starting the controller
+*/�)))!)       �!�+!%) !      �)*+��

%+���5�!                                -��5�!
        !�!
           +-���
                !���
�%      %!-     �)�����+��+     !       %!!5!!�)!+!
+)      %%�+
                %!5                                                                                                                                                                                          )
                   ��)5 !5)!)   %               �)!%
        -
         %)     )       5)�-�
!                               )��!�   !
 -      )!
%-
  !%!   !       !

!��
%)!�%   %%)!    !�      �
%!�))   !)!)!)!%-
�-))!   ��      ��)))!! ��%
�%!)�!)%)�))%              �)           %-%+�
�)      !�5�    !       �               !       -!!
            )%!
��)�)%�)���)

Is this because the baud rate is suddenly changing? Or is it more likely that the output is switching to some proprietary format?

I also didn't have a super solid connection to the board when trying this, could it be that the connection dropped and then reconnected out of sync or something?

Answer 1

In my case it was a flaky connection. I was originally just using jumper wires to make contact into the through holes on the board and hook it up to the bus pirate. I soldered header pins to it and now I can see the output totally clearly.