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MMA8453Q - get readings at time of transient shock?

Question asked by Rich L on Apr 28, 2016
Latest reply on May 3, 2016 by Rich L


Hi everyone,

 

I have a couple of questions surrounding this particular chip. I've read through all the documents I could find in relation to this already (AN 4071, 4076, data sheet etc. as well as the additional sample code). Excuse any misunderstood concepts, I'm new to this, but finding it fun and exciting.

 

Use Case:

  • I want to set the sensor to pick up transient events, i.e. if it has been dropped, thrown etc.
  • I also want to pick up the readings that TRIGGERED the event.
  • I don't mind if it's set to 2/4/8g mode, but I think 4g would be enough for resolution - (realistically, would this even matter as any force above 1-1.5g is quite a big jolt already.)
  • I've set the Latch bit as 1 which I believe should keep the reading (whichever reading that may be...) until it is read.

 

Questions:

  1. With this chip, is the above possible in the first instance?
  2. I'm reading about FIFO data only being available on the mma8451/0Q.
  3. This chip also doesn't allow a read out of the HPF data.
  4. In my implementations, an interrupt event is triggered fairly consistently, but when I try to take a reading from it, the values being returned are so erratic that they're useless. Can only assume this is taking some readings either side of the transient event.
  5. I don't think the Latch data is what I want in this case...
  6. If it's not possible to implement this through the above logic, how else could I achieve the above result, without getting another chip?

 

Thanks in advance!

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