User's Manual

GSM/GPRS Module Series

M85 Hardware Design

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3.7.3. Auxiliary UART Port

 Two data lines: TXD_AUX and RXD_AUX.

 Auxiliary UART port is used for AT command only and does not support GPRS data, multiplexing

function etc.

 Auxiliary UART port supports the communication baud rates as the following:

1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200bps.

 Auxiliary UART port could be used when you send AT+QEAUART=1 string on the UART port.

 The default baud rate setting is 115200bps, and does not support autobauding. The baud rate can be

modified by AT+QSEDCB command. For more details, please refer to the document [1].

Peripheral

TXD

RXD

GND

Module

TXD_AUX

RXD_AUX

GND

Figure 22: Reference Design for Auxiliary UART Port

3.7.4. UART Application

The reference design of 3.3V level match is shown as below. If the host is a 3V system, please change

the 5.6K resistor to 10K.

Peripheral

/TXD

/RXD

TXD

RXD

RTS

CTS

DTR

/RTS

/CTS

GPIO

EINT

GPIO DCD

Module

Voltage level:3.3V

5.6K

GND GND

Figure 23: Level Match Design for 3.3V System