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Gyro FXAS21002 timing

Question asked by Harri Vanhala on Apr 5, 2015
Latest reply on Apr 9, 2015 by Jacques Trichet


I'm going to use FXAS21002 3-axis gyro in car crash test environment (cars, barriers, dummies...).

The plan is to read gyro reading with a steady 500 Hz rate ie. new reading every 2 ms. The rate could be lower down to 200 Hz (5 ms) but according to spesification the FXAS21002 should be able to 500 Hz.

It is vitally important that all 3 axes give there reading at the same instant. I can live with non-simultaneous readings if I know the time difference between the axes?


Could you comment on these questions:


1. The specification sheet does not tell if I can somehow trigger a new measurement cycle. Is it possible to trigger a reading to make a more precise and externally controlled timing?

2. What is the time difference between the readings of the axes?

3. Can an interrupt pin tell whether ALL three axes have a new reading, not just one axis.

4. If I read the three readings is it possible that a new reading is updated in the output register so that one byte is from a previous reading and the other from a new reading? Or eg. the X axis reading is new and the Z axis reading is old.

5. How the sensor actually makes it reading rate (eg. max speed of 800 Hz)? It does not have a clock input. How accurate this rate is?


Best regards


Harri Vanhala

Espoo, Finland