u-blox

IPC - Inter Processor Communication

Multiplexing mode +CMUX

+CMUX
Modules
All products
Attributes
Syntax
PIN required
Settings saved
Can be aborted
Response time
Error reference
partial
No
No
No
-
+CME Error

Description

Enables the multiplexing protocol control channel as defined in 3GPP TS 27.010 [10]. The command sets the parameters for the control channel. The result code is returned using the old interface speed. The parameters become active only after sending the OK result code.
The usage of +CMUX set command during the multiplexing is not allowed.
The multiplexer configuration is as follows:
Table 2. Multiplexer configuration
ModulesControl channelAT commands / data connectionGNSS tunnelingSIM Access Profile (SAP)
LEXI-R10
Channel 0
Channel 1 - 3
SARA-R10
Channel 0
Channel 1 - 3

Syntax

TypeSyntaxResponseExample
Set
AT+CMUX=<mode>[,<subset>[,<port_speed>[,<N1>[,<T1>[,<N2>[,<T2>[,<T3>[,<k>]]]]]]]
OK
AT+CMUX=0,0,,1500,50,3,90
OK
Read
AT+CMUX?
+CMUX: <mode>,[<subset>],<port_speed>,<N1>,<T1>,<N2>,<T2>,<T3>[,<k>]
OK
+CMUX: 0,0,0,1500,253,3,254,0,0
OK
Test
AT+CMUX=?
+CMUX: (list of supported <mode>s),(list of supported <subset>s),(list of supported <port_speed>s),(list of supported <N1>s),(list of supported <T1>s),(list of supported <N2>s),(list of supported <T2>s),(list of supported <T3>s),(list of supported <k>s)
OK
+CMUX: (0),(0),,(1-1509),(1-255),(0-5),(2-255),,
OK

Defined values

ParameterTypeDescription
<mode>
Number
Multiplexer transparency mechanism:
  • 0: basic option
<subset>
Number
The way in which the multiplexer control channel is set up:
  • 0 (default value): UIH frames used only
<port_speed>
Number
Value is ignored.
<N1>
Number
Maximum frame size. The range is 1-1509 and the default value is 31.
<T1>
Number
Value is ignored.
<N2>
Number
Value is ignored.
<T2>
Number
Value is ignored.
<T3>
Number
Value is ignored.
<k>
Number
Value is ignored.

Notes

  • If the multiplexer protocol is not started (the +CMUX set command has not been issued or returned an error result code) and AT+CMEE is set to 2, the +CMUX read command returns the following error result code: +CME ERROR: operation not allowed.
  • For complete compatibility between u-blox products, leave the unsupported/unused parameters blank (which are reported as blank by the +CMUX test command).
  • <T1> must be lower than or equal to <T2>.
  • The multiplexer protocol is supported only on MAIN UART.
  • Each MUX channel configuration stored with AT&W to the personal profile is re-applied everytime the MUX protocol is established.
  • If +USIO configuration is changed, the MUX channels profiles become invalid and shall be restored. For more details, see +USIO notes.
  • GNSS tunneling is not supported.
  • For the configuration of the module power saving during a multiplexer protocol session, see the +UDCONF=201 AT command description.
Last updated: 13 January 2025
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