Evaluation Board User Guide
POWER CONSUMPTION TAB
The Power Consumption tab shows the advantages of using the inactivity and activity functions to modulate system power and obtain overall power savings (see Figure 14).
Figure 14. Power Consumption Tab
When inactivity is detected, caused by acceleration below the amount set in the THRESH_INACT [mg] box for the amount of time set in the TIME_INACT [s] box, the accelerometer is placed into a lower data rate as set in the Inactive Data Rate [Hz] menu. Because the power of the ADXL345 is modulated with data rate, an immediate power savings is acheived. When activity is detected (an acceleration above that set in THRESH_ACT [mg] box), the part is placed back into a higher data rate as specified in the Active Data Rate [Hz] menu.
UG-015
Additionally, the Micro In Calculation indicator lights up, signifying that a controller or microprocessor is actively pulling data from the part or processing it. In addition to power savings from the ADXL345, more power can be saved by powering down the microprocessor during periods of inactivity and using the ADXL345 activity interrupt to wake the microprocessor up during periods of activity.
The ACT/INACT_CTL indicators can be used to enable different axes in the activity or inactivity events. After updating the participating axes, thresholds, timers, or data rates, click the Configure Registers button. The registers are not updated until the button is clicked. Additionally, the button updates the registers only when data acquisition is active. If the button is clicked when no acquisition is occurring, the button remains inactive until it is clicked again or until acquisition is started.
To begin data acquisition, click the Start Acq. button in the bottom left corner of the screen. To end data acquisition, click the Stop Acq. button in the bottom left corner of the screen.
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