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SIM868_Series_Hardware_Design_V1.06 30 2017-07-13
Note: Hardware flow control is disabled by default. AT command “AT+IFC=2, 2”can enable hardware flow
control. AT command “AT+IFC=0,0”can disable hardware flow control. For more details please refer to
document [1].
Table 10: Serial port characteristics
Symbol Min Max Unit
V
2.4 - V
5.5.1. Function of Serial Port
Serial port:
Full mode device.
Contain data lines UART1_TXD/UART1_RXD; hardware flow control lines UART1_RTS/UART1_CTS,
status lines UART1_DTR, UART1_DCD and UART1_RI.
Serial port can be used for GPRS service and AT communication.
Autobauding supports the following baud rates:
1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200bps
Autobauding allows GSM to automatically detect the baud rate of the host device. Pay more attention to the
following requirements:
Synchronization between DTE and DCE:
When DCE powers on with autobauding enabled, it is recommended to send "AT" or "at" or "aT" or "At"
to synchronize the baud rate, until DTE receives the "OK" response, which means DTE and DCE are
correctly synchronized. For more information please refer to AT command "AT+IPR".
Restrictions of autobauding operation:
The DTE serial port must be set at 8 data bits, no parity and 1 stop bit.
The URC such as "RDY", "+CFUN: 1" and "+CPIN: READY” will not be reported.
Note: Customer can use AT command “AT+IPR=x” to set a fixed baud rate and the setting will be saved to
non-volatile flash memory automatically. After the configuration is set as fixed baud rate, the URC such as
"RDY", "+CFUN: 1" and "+CPIN: READY” will be reported when GSM is powered on.
5.5.2. Serial Interfaces
The following figure shows the connection between GSM and client (DTE).
UART1_TXD 1 Transmit data
UART1_RXD 2 Receive data
UART2_TXD 22 Transmit data
UART2_RXD 23 Receive data
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