Submitted by ThomasV on Tue, 07/28/2015 - 19:12
I want to use the Monitor Buffer blocks to gather encoder data (position output of eQEP block when I'm controlling a motor) and write this to a file. Then I will analyze the results in Matlab, so I want no data to be missing.
How can I set up the Monitor Buffer blocks in order to do this? I have tried to start from scratch and just try to write the data of a simulated ramp signal, but the buffer is updated way too slowly. I have attached the diagrams (MonitorBufferTest.vsm) I used. The input to the Buffer Write 0 block is a ramp that goes from 0 to 25 in 25 seconds, the sampling rate is 10 kHz and the buffer size is 1000. As trigger I feed a pulse train with frequency of 10 Hz. The way I see it, this should result in the buffer being rewritten 10 times per second, and there should be 10000 samples in 1 second of data gathering.
Now, when I try to run this in the debug diagram, the buffer is being read at a much lower frequency (I compare that frequency to the pulse train of 10 Hz in the plot on the right side, picture 'BufferTrig.png' is attached).
I assume this means that the MCU doesn't write data to the buffer at 10 kHz, so it takes a longer time to fill the 1000 samples in the buffer. What is the cause of this? Should I configure these blocks in a different way?
Note that my starting point was the 'MonitorBufferTriggerAndTimeCheck.vsm' provided by VisSim, but even then I couldn't get the buffers to work correctly.
Also, if there is a better method for gathering measurement data and writing this to a file without losing some parts, I'd be glad to hear it.
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