Interrupt Configuration TAB

UG-015

The Interrupt Configuration tab is used to demonstrate the built-in functions of the ADXL345. By selecting the functions to enable and configuring the appropriate parameters, the benefits and uses of the interrupts can be examined. This tab is updated whenever an interrupt occurs. This means that some interrupts, such as inactivity, if enabled alone, will not appear to be updated.

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Figure 13. Interrupt Configuration Tab

The Current Status indicators are updated when the panel is first activated and when the Configure Interrupts button is clicked. They show the register values at the time of the read.

The Interrupt System Parameters box is used to set the built- in interrupt parameters. Here, the thresholds for tap or activity events can be set, as well as the many timer values for the interrupt parameters. The units of each are shown after the register parameter name, and entered values are automatically rounded to the nearest valid value.

Evaluation Board User Guide

The indicators for ACT_INACT_CTL and TAP_AXIS are used to select the axes to include in activity, inactivity, and tap events. For more details, refer to the ADXL345 data sheet. Clicking an indicator causes it to toggle values. A lit indicator causes a value of 1 to be written to that bit, and an unlit indicator causes a value of 0 to be written to that bit.

In the Interrupt Configuration box, you can select the interrupts to enable. For purposes of the GUI, all enabled interrupts are mapped to the INT2 pin. Selecting the checkbox next to the appropriate interrupt enables it.

Note that no registers or parameters are updated after setting any individual box or indicator. To configure the interrupts based on new values entered in this box, you must click the Configure Interrupts button in the bottom right corner. Clicking this button updates the Current Status indicators and configures the interrupts as set.

The INT_SOURCE and ACT_TAP_STATUS indicators are updated when an interrupt occurs. The data ready (DR), watermark (WM), and overrun (OR) bits are always set because this tab does not service data-related interrupts. In the configuration shown in Figure 13, the accelerometer has detected inactivity. If the accelerometer were moved with enough force to exceed the 504 mg activity threshold, the INACT indicator would dim and the ACT indicator would light up. If the accelerometer were put down and undisturbed for the 1 sec inactivity timer, the ACT indicator would dim and the INACT indicator would again light up.

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