Ublox SARA-R42, Development Manual

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SARA-R42 - Application note
UBX-20050829 - R02 Local connectivity Page 15 of 58
C1-Public
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The “S et ” command is available only for the auxiliary UART interface.
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The “Read” command is available for both the main UART and the auxiliary UART interfaces.
5.2 AT interface
AT commands can be issued to the module only via UART interface.
By default, the UART data rate is set to 115200 b/s, while “autobauding” is not supported by SARA-R4
series modules.
5.2.1 Set a fixed baud rate
Use the
+IPR
AT command to set a different baud rate for the main UART interface as shown in Table
5 .
Command Response Description
AT+IPR=57600 OK Set UART speed to fixed value 57600 bit/s.
Cellular module response is sent at 115200 bit/s, i.e.
at the original baud rate value.
After the "OK" final result code, wait for at least 200 ms before issuing a new AT command, to guarantee proper baud rate
reconfiguration. Then send commands at the speed just set (57600 bit/s in the example).
The new selected baud rate is immediately applied, a device reboot is not needed.
AT+IPR? +IPR:57600
OK Check the current baud rate
Table 5: Setting a fixed baud rate example
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The UART speed takes around 200 ms to reconfigure itself after a baud rate change through the
+IPR
AT command.
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To show a greeting text at module boot (
+CSGT
AT command), set the desired fixed baud rate
beforehand by using the
+IPR
AT command. If active, the greeting text is shown at boot once, on
any AT interface, the first time the TE sets the DTR line to ON state.
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If using the Direct Link mode in downlink, it is advisable to apply 460800 b/s as fixed baud rate.
5.3 Multiplexer (MUX)
SARA-R4 series modules support the multiplexer functionality on the UART physical link as defined
in the 3GPP TS 27.010
[13] . This makes it possible to have multiple simultaneous sessions (virtual
channels) over the single UART interface.
The following virtual channels are defined:
• Channel 0: multiplexer control.
• Channels 1 to 2: AT commands / data connection.
• Channel 3: GNSS data tunneling (NMEA). 1
For further details about the usage of multiplexer with SARA-R4 series modules, see the Mux
implementation in cellular modules application note
[8] .
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The UART interface takes around 200 ms to reconfigure itself after the multiplexer configuration
through the
+CMUX
AT command.
1 Not supported by SARA-R422 modules