FXOS8700 transient interrupt goes crazy when motion interrupt is enabled!

[MarcoGiammarini]

Hello all!

We are developing a new product with FXOS8700 inside. Into the firmware, we enable both motion and transient interrupt. In this case, the transient interrupt (with a threshold of 1g on all axes) goes crazy and it is enabled continuously. When the motion is not enabled, the transient works correctly. We have the same issue on all our boards (the first batch of 8 pieces).

What's happen? this behaviour is normal or we are doing something wrong?

Regards

Marco

[reyes]

Hi Marco,

I think that the problem is that you are setting a threshold of 1g on all axes, by definition, 1g equals the force of gravity, so, even if the accelerometer is not in movement, it will continue reaching the threshold of 1g due to the force of the earth gravity is applying to your accelerometer’s body.

I recommend you to increase the threshold to around 1.2g and check if this solves the problem.

Have a great day,
Jose

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[MarcoGiammarini]

Hi Jose,

I just check this possibility and the result is the same. The transient acceleration is fired (with high pass filter active) when between two sample the threshold is over.

During my research, I find this: MMA8451 motion and transient detection. Can you check whether the issue is the same for FXOS8700?

Regards

Marco

[reyes · Accepted solution]

 Hi Marco,

Yes, it is the same issue since the FXOS8700 have embedded the same structure than the MMA8451.

So, unfortunately it is not possible to o use the motion and the transient detection functions together.

Sorry about that.