How to make Nested while loops faster

I am running a while loop that is scanning the serial port for data. This while loop is inside a bigger while loop that is continuously acquiring data from an instrument (a spectrometer).

The smaller while loop that scans the port continuously writes to a file until the while condition becomes False. I have noticed that this while loop takes so much time that it interferes with the data acquisition from the spectrometer. I use the commands fread(s) to read from serial port object s and fwrite to write to file. Both these processes seem extremely slow and compromise data acquisition.

Is there a way to speed this up? Is there something I can use that is faster than fread? Should I be writing an array instead of to a file? If so, how do I write to an array during a while loop where I'm unsure of how big the array will be beforehand...

Answer 1

[Walter Roberson]

It sounds as if you should be using a BytesAvailableFcn to trigger a callback when there is data available, and when there is, read BytesAvailableFcnCount worth of data.

[Maheen Siddiqui]

Thanks for your reply. Do you think the fread should be initiated inside the callback function? Or in the script where the serial object is defined and opened and that calls the callback function?