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To adjust the backlight brightness, you can configure the sink current of the four current sink drivers
via software.
For LCM0, use the internal backlight driving circuit provided by SA800U-WF by default. For LCM1, you
can use the internal circuit or an external backlight driving circuit according to your demand. The following
is a reference design for LCM1 external backlight driving circuit where PWM_PMI_GPIO5 is used to
adjust the backlight brightness.
PWM_PMI_GPIO5
Module
Figure 24: Reference Design of LCM1 External Backlight Driving Circuit
3.19. Touch Panel Interface
SA800U-WF provides one I2C interface to connect with touch panel, and also provides the corresponding
power supply and interrupt pins. The pin definition of touch panel interfaces is illustrated below.
Table 22: Pin Definition of Touch Panel Interface
Pin Name
LDO28A_3V0
LDO14A_1V88
TP_INT
TP_RST
TP_I2C_SCL
TP_I2C_SDA
SA800U-WF_Hardware_Design
VBAT
C1
R1
μ
2.2
10K
Pin No
I/O
Description
J4-10
PO
3.0 V output for VDD of TP
1.8 V output for TP I2C
J4-9
PO
pull-up circuit
J2-48
DI
TP interrupt
J2-50
DO
TP reset
J2-44
OD
TP I2C clock
J2-46
OD
TP I2C data
Backlight Driver
F
Smart Module Series
SA800U-WF Hardware Design
LCM1_LED+
LCM1_LED-
Comment
Vnom = 3.0 V
I
max = 150 mA
O
Vnom = 1.8 V
I
max = 50 mA
O
1.8 V power domain.
67 / 106
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