M12 Hardware Design
M12_Hardware_Design_V3.3
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Used for AT command, GPRS data, CSD etc. Multiplexing function is supported on the
UART Port. So far only the basic mode of multiplexing is available.
Support the communication baud rates as the following:
300,600,1200,2400,4800,9600,14400,19200,28800,38400,57600,115200.
The default setting is autobauding mode. The following baud rates are supported for
autobauding function: 4800, 9600, 19200, 38400, 57600, 115200.
The module disable hardware flow control by default, AT command “AT+IFC=2,2” is used to
enable hardware control.
After setting a fixed baud rate or autobauding, please send “AT” or “at” string at that rate. The
UART port is ready when it responds “OK”.
Autobauding allows the module to detect the baud rate by receiving the string “AT” or “at” from
the host or PC automatically, which ensures module flexibility without considering which baud
rate is used by the host controller. Autobauding is enabled by default. To take advantage of the
autobauding mode, special attention should be paid according to the following requirements:
Synchronization between DTE and DCE
:
When DCE (the module) powers on with the autobauding enabled, it is recommended to wait 2 to
3 seconds before sending the first “AT” string. After receiving the “OK” response, DTE and DCE
are correctly synchronized.
If the host controller needs URC in the mode of autobauding, it must be synchronized firstly.
Otherwise the URC will be discarded.
Restrictions on Autobauding operation
The UART port has to be operated at 8 data bits, no parity and 1 stop bit (factory setting).
The A/ and a/ commands cannot be used.
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” or “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
Note:
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 Section “AT+IPR”
in document [1].
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