Smart Machine Smart Decision
TXD
RXD
RTS
CTS
UART _DTR
UART _ DCD
UART1_RI
TXD
RXD
RTS
CTS
DTR
DCD
RING
MODULE (DCE)
CUSTOMER (DTE)
Serial port
Serial port
Figure 19: Connection of the serial interfaces
If the voltage of UART is 3.3V, the following reference circuits are recommended. If the voltage is 3.0V, please
change the resistors in the following figure from
5.6K to 14K.
Figure 20: Resistor matching circuit
If the voltage of UART is 3V or3.3V, the following reference circuits are recommended:
SIM800H_Hardware_Design_V1.01
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2013-08-20
