Question about ADcmXL3021 sample rate

hi,  i am new in signal processing, and i've got some questions when using ADcmXL3021.

i want to use MTC mode for collecting axis's time domain data, for datasheet says "For MTC mode, the sampling rate is always 220 kSPS and captures 4096 samples", if all of the AVG_CNT, FILT_CTRL all setting default, so does it mean that every second i can collect 4096 data for each axis? like i catch 4096 data every second from the X_buffer/Y_buffer/Z_buffer. Also the pic show that each buffer save N=4096.

also, for above question, I want to further explain what I have discussed so far that is 4096 samples means for 1s i will have 4096x220ksps data? or just 1s get 4096 data.

if REC setting default 0x1102, so means i am using SR3?

so according above, my AVG also setting default, and according to the formulate, my sample rate is 220000/2^7 = 1718 sps?

and where can i set DIN?? mentioned in above picture(for example, set DIN=0xBB35...)

hope to realize those relationship for it....

best regards and thanks.



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[edited by: yuyuff at 8:46 AM (GMT -4) on 22 Apr 2021]
  • 0
    •  Analog Employees 
    on Apr 28, 2021 11:28 AM

    Hi YuYuff,

    Sorry for a bit late reply. 

    4096 is the number of samples, if there are no averaging, 4096 is going to be for 18.62 msec (=4096/220,000).
    Depending the number of averaging it scales. For instance, if AVG_CNT = 5, every 32 (2^5) samples in time domain are averaged to make one of the 4096 samples.  In other words, the sample time is now 595.8 msec.

    REC_CTRL 0x1102 (default) means  [0001]; [0001]; [0000]; [0010]. and second 0001 refers to SR0.
    You can check Table 55 again.

    DIN is Data_in, see pages 5 and 6. 
    It is actually MOSI, where your processor is the master, ADCMXL3021 is the slave.

    Hope these help.

  • hi hunl,

    Thanks for your respond!

    So it means that if there are no averaging, i can get almost 53(=1/18.62ms) continuously data with full 4096 samples? (means total 53*4096 data in 1 sec)

    And, 220kSPS, sps means sample per second? then how can it only get 4096 samples?

    sorry i am really new in digital processing...

    Thanks again in advance.

  • 0
    •  Analog Employees 
    on Jun 13, 2021 12:05 AM in reply to yuyuff

    Hello

    The MTC mode does not provide data on a continuous basis.  While in this mode, the ADcmXL3021 can NOT support data capture and communication with a master processor, at the same time, so it will not be possible to get 53 time records, in a 1 second timeframe.  If that is your desire, then you need to use the Real Time Sampling (RTS) mode.  In the mode, the ADcmXL3021 captures 4096 samples, at a rate of 220kSPS, for each axis, simultaneously.  Once the capture is complete, your processor can read the data from the buffers, then trigger another capture.  Does that help?

    Best, NevadaMark