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3. The Duration of Change Outside Threshold is related to the Ambient Light Threshold.
Once an ambient light change exceeds the threshold, the change must persist for a
certain period of time. This feature filters large changes in light such as a shadow moving
across the light sensor and prevents display "bouncing."
TAOS suggests exposing Backlight Transition Speed, Ambient Light Threshold, and Duration of
Change Outside Threshold on a user interface in order to provide some level of end-user
customization. Alternatively, the designer can hard-code these values to best fit their application.
The Advanced dialog also includes an 'Option' menu item which allows the user to select which
package type (TMB or chipscale) is being evaluated and whether to turn on/off the LEDs on the EVM.
When deriving lux, the lux equation is similar for both TMB and chipscale packages, but two distinct
equations are provided to optimize the illuminance value for the different package types. The LED(s)
on/off item is provided to eliminate the interference of the LED reflections at low light levels when the
EVM is covered. The green LED indicates power, and the red LED indicates if an interrupt event has
occurred. The LEDs will always be disabled at the start of the demo application and must be manually
selected in order to turn on the LEDs.
The TSL2560 application also supports a Monitor dialog (see Figure 4) that displays the illuminance,
channel 0 and channel 1 values, interrupt threshold, auto-range, and the display brightness setting of
a "simulated panel". The remaining battery life and relative power (relative to maximum backlight
brightness) are also displayed.
An Evaluation System for the TSL2560/61 Ambient Light Sensor
Figure 4. Automatic Brightness Control Monitor Dialog
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