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The following figure is an example of connection between SC20-WL and PC. A voltage level translator
and a RS-232 level translator chip are also recommended to be added between the module and PC, as
these two UART interfaces do not support the RS-232 level, while support the 1.8V CMOS level only.
1.8V
UART1_TXD
UART1_RTS
UART1_RXD
UART1_CTS
GND
Module
NOTE
UART2 is similar to UART1. Please refer to UART1 reference circuit designs for UART2's.
3.11. SD Card Interface
SC20-WL module supports SD cards with 4-bit data interfaces or SDIO devices. The pin definition of the
SD card interface is shown below.
Table 9: Pin Definition of SD Card Interface
Pin Name
Pin No.
SD_LDO11
38
SD_LDO12
32
SD_CLK
39
SC20-WL_Hardware_Design
OE
VCCA
VCCB
TXD_3.3V
TXD_1.8V
RTS_3.3V
RTS_1.8V
RXD_1.8V
RXD_3.3V
CTS_1.8V
CTS_3.3V
GND
TXS0104EPWR
Figure 16: RS232 Level Match Circuit (for UART1)
I/O
Description
PO
Power supply for SD card
1.8V/2.95V output power
PO
supply
High speed digital clock
DO
signal of SD card
3.3V
VCC
DIN1
DIN2
DIN3
DIN4
DIN5
ROUT1B
ROUT1
ROUT2
ROUT3
FORCEON
/INVALID
3.3V
/FORCEOFF
SN65C3238
Comment
Vnorm=2.95V
I
max=600mA
O
Support 1.8V or 2.95V power supply.
The maximum drive current is 50mA.
Control characteristic impedance as
50Ω.
Smart Wi-Fi Module Series
SC20-WL Hardware Design
GND
GND
DOUT1
RXD
DOUT2
CTS
DOUT3
DOUT4
DOUT5
TXD
RIN1
RIN2
RTS
RIN3
DB-9
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