Serial Interfaces - SimCom SIM800L Hardware Design

The default setting is autobauding.

Autobauding allows SIM800L 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 SIM800L is powered on

Serial Interfaces

4.5.2
The following figure shows the connection between module and client (DTE).
Module(DCE)
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.
SIM800L(MT6261)_Hardware Design_V1.01
.
Serial Port
TXD
RXD
RTS
CTS
DTR
DCD
RI
GND
Figure 20: Connection of the serial interfaces
Smart Machine Smart Decision
Customer(DTE)
Serial Port
TXD
RXD
RTS
CTS
DTR
DCD
RING
GND
29 2016-07-07