Smart Machine Smart Decision
TXD
RXD
TXD
RXD
MODULE (DCE)
Serial port
GND
I/O Connector
GND
PWRKEY
PWRKEY
Figure 25: Connection for software upgrading and debugging
The serial port and the debug port support the CMOS level. If user connects the module to the computer, the
level shifter should be added between the DCE and DTE.
4.5.5
Multiplexing function of serial port
If full modem is not necessary, it could be multiplexed into two serial ports without flow control, the details
could be found in the following table:
Table 11: Multiplexing function of serial port
Pin name
Pin number
Mode 0(default)
Mode 1
UART_DTR
69
UART_DTR
GPIO22
UART_RI
68
UART_RI
GPIO23
UART_DCD
70
UART_DCD
GPIO24
CTS
34
CTS
URXD2(IN)
RTS
33
RTS
UTXD2(OUT)
TXD
32
TXD
UTXD1(OUT)
RXD
31
RXD
URXD1(IN)
Note: Multiplexing function need different software supply.
SIM800H_Hardware_Design_V1.01
34
2013-08-20
