Ambient Light Sensor
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“ALS” Sub Tab
The ALS tab shows the registers associated with ambient light sensing control. Register values in hex
are shown on the left, preselected values are available in list boxes in the middle, and actual values
are shown on the right.
• ATIME Register (0x01) controls the
ALS integration time. The actual time
is:
(256-ATIME) * 2.72 ms
Note: The column on the right is the
computed value for ATIME and is always
correct. Sometimes the value shown in the
list box will be one of the preselected
values but it has not been selected. If this
happens the number will not be the same
as the computed number for WTIME on
the Control Sub-Tab. The computed value is the one that is correct. This can be fixed by
selecting a preselected value from the list box or by cycling the register value UP/DOWN or
DOWN/UP. This will set the list box value or clear the value from the list box so the screen is
correct.
• Control Register (0x0F) – Controls the ALS gain settings.
1. AGAIN – Adjusts the ALS input gain. Valid values are 1x, 8x, 16x, and 120x.
2. AGL – ALS Gain Lowered. Reduces ALS gain by a factor of 6. This feature can only be
used when AGAIN is set to 1x or 8x. It does not function for higher gain levels.
“ALS Interrupt” Sub Tab
This tab contains the settings for controlling the generation of ALS interrupts to a control processor.
The AILT and AIHT values are 16 bit
thresholds for the upper and lower trigger
points. Each is set using two 8-bit registers.
Another control (APERS) establishes the
required persistence of the interrupt signal.
Also on this screen is a button that will
automatically generate the register values to
provide threshold settings 25% higher and
lower than the currently measured amount of
ambient light.
• ALS Interrupt Low Threshold (0x04, 0x05) – Low light threshold for ALS interrupt.
1. AILTL (0x04) – The lower 8 bits of the 16 bit low threshold value.
2. AILTH (0x05) – The upper 8 bits of the 16 bit low threshold value.
• ALS Interrupt High Threshold (0x06, 0x07) – High light threshold for ALS interrupt.
1. AIHTL (0x06) – The lower 8 bits of the 16 bit high threshold value.