Autobaud detection

[Scarr]

Hi,

Is there anyway of determining the baud rate of RS232 using a scope or logic probe? also parity / stop bits etc.

Thanks

Steve

 

[dougy83]

Yep, with a 'scope, measure the period of the shortest high or low time - that will generally be your bit time. Bit rate = 1/(bit time)

Do you have any control over what is been sent? If not, then you'll have to capture a character (generally after an idle period), and given enough attempts, you should be able to work out the parity. There are generally 1 or more stop bits and can be worked out if you can capture 2 contiguous characters.

 

[Sceadwian]

The easiest way would be to send capital letter U's from the sending terminal, if you have the UART set to 8n1 you'll get the bit pattern 1010101010 on the UART TX pin, makes it very easy to see on a scope, keep in mind RS232 is active LOW.