GSM/GPRS Module Series
M85 Hardware Design
M85_Hardware_Design Confidential / Released 39 / 88
If the host controller needs URC in the mode of autobauding, it must be synchronized firstly. Otherwise
the URC will be discarded.
2. Restrictions on autobauding operation
The UART port has to be operated at 8 data bits, no parity and 1 stop bit (factory setting).
Only the strings
―
AT
‖ or ―
at
‖ can be detected (neither ―
At
‖ nor ―
aT
‖).
The Unsolicited Result Codes like ―
RDY
‖
,
―
+CFUN: 1
‖ and ―
+CPIN: READY
‖ will not be indicated
when the module is turned on with autobauding enabled and not be synchronized.
Any other Unsolicited Result Codes will be sent at the previous baud rate before the module detects
the new baud rate by receiving the first
AT
string. The DTE may receive unknown characters after
switching to new baud rate.
It is not recommended to switch to autobauding from a fixed baud rate.
If autobauding is active it is not recommended to switch to multiplex mode.
To assure reliable communication and avoid any problems caused by undetermined baud rate between
DCE and DTE, it is strongly recommended to configure a fixed baud rate and save it instead of using
autobauding after start-up. For more details, please refer to the Section
AT+IPR
in
document [1]
.
3.7.1.2. The Connection of UART Port
The connection between module and host using UART Port is very flexible. Three connection styles are
illustrated as below.
Reference design for Full-Function UART connection is shown as below when it is applied in
modulation-demodulation.
TXD
RXD
RTS
CTS
DTR
DCD
RI
TXD
RXD
RTS
CTS
DTR
DCD
RING
Module (DCE)
Serial port
UART port
GND
GND
PC (DTE)
Figure 17: Reference Design for Full-Function UART
NOTE