AnsweredAssumed Answered

FXAS21002C : Integration Query

Question asked by RIscy Payne on Nov 15, 2015
Latest reply on Nov 15, 2015 by Mark Pedley



I have reviewed the datasheet and information within freescale resources, I wish to query about the integrator/intergration of the gryo movement. It is used for navigation with Accel (3rd party precision) and Mag (FXOS)


I currently have circular buffer 128 frame which take 2.4 second to populate (18.75mSec Sample rate). The FXAS take minimum 3.5mSec before data ready interrupt occurred but with other sensor and ADC constraint, the minimum rate is 18.75mSec.


I wish to do away the circular buffer and take 2.5 second sample, so that MCU can be put to sleep for 2.5 second and then wake up for capture data and so on, this save power since it run on battery. However the minimum ODR is 12.5Hz for FXAS21002C which may not be possible.


I'm quite unclear what internal integrator is doing for various output sample rate?


Does it hold rate of change dps between output sample rate? or it basically snapshot of dps?


As an example, I can put to 12.5 Hz sample rate (which is 80mSec) , if there is sudden change of 30deg/Sec say at 20mSec point and then no angular change (60mSec before data ready INT (say)), does it actually hold the 30deg/Sec reading (due to internal integrator) by the time it reach to output data buffer or I get 0deg/Sec readout, since it snapshoot.


When sample it taken does it clear the old information?


I'm open for suggestion, idea how to minimize power rather than constantly sampling the data all the time.


Thank you for calcification.




Update: Noting that FXAS has build in FIFO buffer which 32 frame of data is stored, this mean 80mSec sample rate which take 2.56Sec, This is perfect!!!. My question about integrator and sudden angular rate change remains...