I have problem with getting data from a sensor using serial communication rs-232. The problem is fscanf takes much time. There is profiler result below.
time calls for i=1:1:1501 2.61 1501 Out(i,1) = eval(fscanf(s)); 0.01 1501 end
The sensor provides data(13X1 char) when it is called. I used a for-loop to acquire whole data (1501X13)
1501 calls increase its time. If I reduce the number of calls, the accuracy will be reduced. I want to have high accurate data that means I need to call 1501 times. Is there any way to make fscanf faster? OR any better code to get data faster in serial communication?
Thanks in advance.
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15 years ago, I would use fread and "format" the data myself. I don't know how the technology evolved, but my guess is that fscanf, which is quite flexible and powerful, generates a significant overhead.
The list of functions dedicated to managing serial com. can be found here: http://www.mathworks.com/help/matlab/serial-port-devices.html
One additional point, do you really need to format the data "real time" as you receive it? Couldn't you just buffer it for a moment and then format the whole in one shot if really needed? On this matter, you could read the doc of fread, in particular the section about InputBufferSize.
EDIT after seeing your screenshot.
If you read directly 1501 floats with fscanf() or 1501*13 char or uint8 with fread(), you don't need the loop at all for reading the whole stream.
One thing that could happen in your profiling (but I am unsure now, because I've not been playing with serial coms for a long time) is that both fscanf() and fread() are blocking methods that won't return before they get the exact amount of data that you ask them to receive. So in all three cases, the 2.6x seconds that you are measuring are the time that it takes internally to receive 1501*13 bytes (for your bit-rate setting), plus a little overhead due to MATLAB processing. And the overhead is almost not visible because MALTAB format processing goes much faster than usual serial communications.
You do not know you are testing the speed of fscanf(): you might be testing the speed of eval(). Are you certain you need eval?
Has anybody a new answer to the latest question here? Why this error might be produces "Unsuccessful read: OBJ must be connected to the hardware with FOPEN." while the port is already open and ready to use?