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EZ430 RF2560 accelerometer sample rate issue (CMA3000)

Mark Joseph
Prodigy 180 points


Hello All,

I was wondering if anyone else has encountered a similar problem to mine. The CMA3000 is programmed to be in the 400Hz ODR mode. I then have the device attached to a shaker for calibration. The shaker is oscillates at a 4Hz sine wave. To me this means I should have 100 data points per 4Hz cycle. Unfortunately I have 10 data points per 4HZ cycle. This indicates that the CMA3000 ODR is programmed at 40Hz. Not sure whats going on. As a side note I pulled the data into matlab and took an fft at using 40Hz sample rate and also tried 400Hz sampling rate and sure enough the 40Hz is spot on. Like I said I was wondering if this is a known issue, or something I may be missing. Thanks in advance.

  • 0
    Prodigy 180 points

    I should also mention,  I am using a reference accelerometer with a dynamic signal analyzer to calibrate the ez430 rf2560's cma3000. The reference accelerometer produces the correct tone at 4Hz on the SA. The data collected from the CMA3000, when the fft is taken, produces a tone at roughly 4.25Hz. THis is also troublesome in my mind. I am aware of a bug in the VTI CMA 3000 that will produce junk readings unless the interrupt is used properly. From what I can tell the accelerometer application in TI's sdk uses the interrupt to read the CMA. Is this correct? or is the CMA polled?

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