Circuit Descriptions
7.
The ARM controller communicates with the LED drivers (on
each AL module) via an SPI bus. For debugging purposes, the
working principle is given below:
•
Data from the ARM controller is linked through the drivers,
which are connected in cascade
•
SPI CLK, SPI LATCH, PROG, BLANK and PWM CLOCK
are going directly from the controller to each driver
•
SPI DATA RETURN is linked from the last driver to the
controller: controller decides which driver returns data.
7.8.3
Temperature Control
Refer to
for signal interfacing between the ARM
controller and the temperature sensor on the AL boards.
Figure 7-15 Communication between ARM controller and
temperature sensor
Each AL board is equipped with a temperature sensor. If one of
the sensors detects a temperature over the threshold, the
TEMP line is pulled LOW which results in brightness reduction.
7.9
“White LED” Backlight
In this chassis, the backlighting of the LCD is done by LEDs.
This enables controlled backlighting of the LCD. The LEDs are
regulated by monitoring the LVDS signal with the PNX51xx.
The PNX51xx then controls the power supply to the “matrix
connected” LEDs via the I
2
C bus.
1
83
10_206_090
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