Flowcode Support Board

HI, I'm battling UART and my trusted method to check Baud is to measure the width of a bit using a scope.
When sending 0x55, I have always used the Cursors to measure a single high or low pulse width.

I'm getting some subtle timing errors so I thought I would check my basic method with google, then ChatGPT (sorry, I know!)
but ChatGPT gave this method that measures the PERIOD of the wave form...surely this is wrong?

ChatGPT gives...

3. Correct Measurement Technique
Send a repeating character (0x55 ideal), because it produces a clean alternating bit pattern (10101010).
Set the oscilloscope trigger on a falling or rising edge.
Zoom in until you see several adjacent bit transitions.
Use cursor Δt or automated period measurement between two similar edges (e.g., rising → next rising).
Convert the measured Δt into baud = 1/(Δt).


Below is the Methods I beleive to be the propper measurement technique. (image robbed from internet!) thoughts? J.

Yep, AI is wrong, as usual
Depends what you asked though.
Your screen shot method is correct for UART baud.

Thanks for the clarification Leigh! exactly what I needed.

Fair Point regarding the question, everything is down to interpretation.
I asked "when measuring UART baud rate with an oscilloscope do you measure the period or pulse width"
hey ho. J.

Hi J.
This is what I have stated in the past.

medelec35 wrote: ↑

Fri Feb 24, 2023 8:28 am

If you have a scope or a logic analyser Just send an upper-case U and measure either one bit mark or space duration, then baud rate = 1/mark or space duration.