ADcmXL3021 Questions

Question

Hi, my customer has the following questions as shown below: 
 
 On data sheet page 23 table 20, there are eight (0-7) options for AVG_CNT settings. Whereas on page 41 table 89, there are only seven (1-7) options. Which one is the right one?; 
 He would like to do real time streaming measurement but with a sampling rate lower than 220 kSPS which is not available in RTS mode.
 
 Can he set MTC mode to behave like RTS mode but with lower sampling rate?

On the sensor&rsquo;s feature, it is said that 10 data records for each axis can be stored. Does it mean 10 x 4096 data per axis? How to retrieve the data which are stored in flash? 
 
 On data sheet page 23 of ADcmCL3021 datasheet: "For MTC mode, the sampling rate is always 220 kSPS and......". However, in page 41 : in AVG_CNT, DECIMATION CONTROL says "......These sample rate settings only apply to MFFT, AFFT,and MTC mode.". It looks like contradictory , please kindly explain with examples.

Please kindly help to advise those questions above. 
 Thank you very much and have a blessed day!

John.Tuazon · Accepted Answer

Hi JPLimAlex , 
 Thank you for your query! Both are the right tables for the AVG_CNT settings. Table 89 uses the AVG_CNT for the sample rate settings. Table 20 relates the AVG_CNT settings to the frequency bin sizes of FFT. 
 I'll ask a colleague for the resolution of your 3 other questions. Best regards, John)

ZiyaErdemir · Answer

JPLimAlex said: He would like to do real time streaming measurement but with a sampling rate lower than 220 kSPS which is not available in RTS mode. 
 Datasheet has plenty of wrong explanations and informations. For the RTS sampling rates (default 220kSPS) has decimation settings at RT_CTRL register (see table 56 and 57). You can define sampling rate either by N (number of averages) or by fixed preselected sampling rate ( at 20, 40, 60, 80, 100, 120, 140 and 160 kSPS). The decimation or sample rate options are in effect only if Bit 7 of RT_CTRL is enabled.

ZiyaErdemir · Answer

JPLimAlex said: He would like to do real time streaming measurement but with a sampling rate lower than 220 kSPS which is not available in RTS mode. 
 
 As I understand from the datasheet, No. In MTC mode, during sampling filtering, decimation, null data offsetting / after sampling completed other steps like statistical calculations, alarm checking, storing etc. are done. In RTS mode there is no such steps after sampling so real time data are streamed. That means in MTC mode due to calculaton period, data collection can not be done (unless there is dual core microcontroller used in ADcmXL3021, or, Analog data collection is done by direct memory access from peripheral to the memory while calculation performed by fast cpu).

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