Quectel M66

GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 38 / 80
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, 115200.
 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 19: 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 20: Level Match Design for 3.3V System
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