Hi,
Thank you for your question. BMA253 slope (or any-motion) interrupt uses the difference between two successive samples as input, which is the current sample minus the previous sample, the next sample minus the current sample, etc. When the difference or slope is beyond the slope_th threshold for the amount of slope_dur duration, the slope interrupt will be triggered. Once the condition is no longer valid, the slope interrupt will be cleared automatically.
For example, if you set slope_th to 5 LSB at +/-4g range, then it means the slope_th threshold is 5*7.81 = 39.05mg. If you set slope_dur to 2, then it means there should be 3 samples of the difference go beyond the slope_th in order to generate the slope interrupt. If you use 7.81Hz or 15.63Hz bandwidth, then it will be very difficult for BMA253 to generate slope interrupt. You should use 1000Hz bandwidth and/or change slope_dur to 0 meaning that whnever there is one sample of the difference goes beyond the slope_th, the slope interrupt will be generated.
In addition, the slope interrupt is sensitive to tapping motion, hitting motion or fast shaking motion, etc. If you wave the device in the air slowly, then you won't be able to see the slope interrupt because the difference is not too much. What you can do is monitor the rising edge or falling edge of the slope interrupt signal on one of the two interrupt output pins to count how many times the slope interrupt has been triggered.
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