± 2g / 4g / 8g / 16g Tri-axis Digital
Accelerometer Technical
Reference Manual
PART NUMBER:
KX132-1211
Rev. 1.0
31-Jul-2019
36 Thornwood Dr.
–
Ithaca, NY 14850
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All Rights Reserved
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2.5
Sample Buffer Feature Description
The sample buffer feature of the KX132-1211 accumulates and outputs acceleration data based on how it is configured.
There are 3 buffer modes available, and samples can be accumulated at either low (8-bit) or high (16-bit) resolution.
Acceleration data is collected at the ODR specified by OSA[3:0] in the ODCNTL register. Each buffer mode accumulates
data, reports data, and interacts with status indicators in a slightly different way.
FIFO Mode
Data Accumulation
Sample collection stops when the buffer is full.
Data Reporting
Data is reported with the oldest byte of the oldest sample first (X_L or X based on
resolution).
Status Indicators
A watermark interrupt occurs when the number of samples in the buffer reaches the
Sample Threshold. The watermark interrupt stays active until the buffer contains less
than this number of samples. This can be accomplished through clearing the buffer or
explicitly reading greater than SMPX samples (calculated with Equation 10).
BUF_RES=0:
SMPX = SMP_LEV[9:0] /3
– SMP_TH [7:0]
BUF_RES=1:
SMPX = SMP_LEV[9:0] /6
– SMP_TH [7:0]
Equation 10:
Samples Above Sample Threshold
Stream Mode
Data Accumulation
Sample collection continues when the buffer is full; older data is discarded to make
room for newer data.
Data Reporting
Data is reported with the oldest sample first (uses FIFO read pointer).
Status Indicators
A watermark interrupt occurs when the number of samples in the buffer reaches the
Sample Threshold. The watermark interrupt stays active until the buffer contains less
than this number of samples. This can be accomplished through clearing the buffer or
explicitly reading greater than SMPX samples (calculated with Equation 10).
Trigger Mode
Data Accumulation
When a physical interrupt is caused by one of the digital engines or when a logic high
signal occurs on the TRIG pin, the trigger event is asserted and SMP_TH[7:0] samples
prior to the event are retained. Sample collection continues until the buffer is full.
Data Reporting
Data is reported with the oldest sample first (uses FIFO read pointer).
Status Indicators
When a physical interrupt occurs and there are at least SMP_TH[7:0] samples in the
buffer, BUF_TRIG in BUF_STATUS_2 is asserted.