GSM/GPRS Module Series
M85 Hardware Design
M85_Hardware_Design Confidential / Released 42 / 88
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
1K
TXD
RXD
RTS
CTS
DTR
RI
/RTS
/CTS
GPIO
EINT
GPIO
DCD
Module
1K
1K
Voltage level:3.3V
5.6K
5.6K
5.6K
1K
1K
1K
1K
GND
GND
Figure 23: Level Match Design for 3.3V System