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Configuration and Operation
M9328MX21ADSE User’s Manual, Rev. A
2-8 Freescale Semiconductor
Figure 2-8. Ethernet Interface
2.3.7 Touchscreen ADC
The ADS is equipped with an Analog Devices AD7873BRQZ ADC. The ADC communicates with the
touchscreen of the LCD on the Base board. Variable resistor VR1 on the Base board can be used to change
the VBAT input voltage to the ADC. The i.MX21 communicates with the ADC via the CSPI1 interface.
Setting S1-7 to ON connects CSPI1_SS0 to the ADC chip select. Setting S1-8 to ON connects the ADC
interrupt out to UART3_CTS. Figure 2-9 shows the ADC interface.
Figure 2-9. ADC Interface
CS8900A-CQ3Z
RJ45 Connector
Isolation
Transformer
i.MX21
CS_LAN
BA1..3
D0..15
B_OE
B_RW
B_DQM3_EB3
UART3_RTS
SBHE
IOW
IOR
AEN
D0..15
INTRQ0
SA8
SA9
SA0
SA4..7
SA10..19
SA1..3
V
CC
CHIPSEL
P9
Y+
X+
V
CC
X-
Y-
LCD CONNECTOR
P7
VBAT
CS
DCLK
DOUT
DIN
i.MX21
UART3_CTS
PENIRQ
S1
CSPI1_SCLK
CSPI1_MISO
CSPI1_MOSI
CSPI1_SS0
VREF
VR1
AD7873BRQZ
8
7