Robin2:
Your calculation is fine.How are you collecting the data? And do you have examples of the raw data for a few different baud rates?
My wild guess is that it is your Matlab stuff that is determining the throughput rather than the baud rate. By the way I have no experience of Matlab.
...R
I tried on different serial monitors-terminals, such as Putty, realTerm and Arduino Serial Monitor with same result. But I didn't save the results.
Now I made a different test, on my workshop computer instead my Laptop, with an Arduino Mega 2560 at three different baudrates: 115200, 230400 and 1000000.
I upload RAW data for these baudrates on that Mega 2560(with timestamp-from Arduino IDE monitor). I pasted it onto Excel file on three different pages (one for each baudrate) and its respective baudrate calculations. As you can see, the number of samples did not increased a lot as should be expected, and the baudrate it's quite similar.
I don't know how to upload a file here, so I put a Dropbox link:
https://www.dropbox.com/sh/avkbgu7y213lss0/AAA_CMHEpbLSqpW7OVZwjgfPa?dl=0
In all ways, I got better results on my laptop (It has better resources than this computer). And like there, I can't reach more than 115200bps.
Thank you for your support.