how to read steaming data from a serial port?

Hello, I'm trying to read data off an IMU device connected through a serial port to matlab. I know that each line of new data starts with the header 'AA 55', and has 38 bytes including the header. I am trying to read the data within a loop, but the data's size changes each loop. How can I make sure i get just the 38 bytes each time starting with the known header?

Thanks.

Answer 1

[Walter Roberson]

Once you are positioned just before the AA, then fread(s, 38, 'uint8')

You will have wanted to set the port BytesAvailableFcnMode to 'bytes'

[Orel Levy]

thanks, that did the trick

[muhammad faiz]

how do you position to get the header (AA in your case)?

[Walter Roberson]

the easiest approach involves wasting an input line . fread one byte at a time until you find AA hex . fread another byte and verify it is 55 hex. if not go back to the AA check . once you have seen AA55 then fread 36 more byte . You can now switch into reading groups of 38 bytes .

This is the easiest way . Slightly more difficult to code would be to make use of those 36 bytes instead of throwing them away .

You might need to send something to provoke the mcu to start sending data .