Auxiliary Uart Port; Uart Application - Quectel M85 User Manual

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].

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
Voltage level:3.3V
M85_Hardware_Design
Module
TXD_AUX
RXD_AUX
GND
Figure 22: Reference Design for Auxiliary UART Port
1K
/TXD
1K
/RXD
1K
/RTS
1K
/CTS
1K
GPIO
1K
EINT
1K
GPIO
GND
Figure 23: Level Match Design for 3.3V System
Confidential / Released
Peripheral
TXD
RXD
GND
5.6K
5.6K 5.6K
GSM/GPRS Module Series
M85 Hardware Design
Module
RXD
TXD
RTS
CTS
DTR
RI
DCD
GND
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