CMUX_User_Guide
CMUX User Guide 30268ST10299A Rev. 0 - 13/10/06
CMUX User Guide 30268ST10299A Rev. 0 - 13/10/06
This document is refered to the following products:
GM862-GPS 3 990 250 657 GE863-GPS 3 990 250 660
GM862-QUAD 3 990 250 659
GM862-QUAD-PY 3 990 250 658
GE863-OUAD Pb balls 3 990 250 662
GE863-PY Pb balls 3 990 250 661
GE864-QUAD 3 990 250 675
GE864-PY 3 990 250 676
GE863-QUAD 3 990 250 648
GE863-PY 3 990 250 650
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 Contents
1INTRODUCTION (4)
1.1Scope of document (4)
2APPLICABLE DOCUMENTS (5)
3TECHNICAL CHARACTERISTICS (6)
3.1Product architecture (6)
3.2Implementation feature and limitation (6)
3.3AT command interface interactions (6)
4SERIAL MULTIPLEXER PROTOCOL (8)
4.1CMUX Frame Structure (8)
4.2UIH Control Channel Frame Coding (11)
4.3UIH Data Channel Frame Coding (13)
4.4CMUX establishment scenario (14)
5TELIT SERIAL PORT PC INTERFACE FOR CMUX (15)
5.1Interface Specification (15)
5.2Scenario (15)
5.3Graphical Interface (16)
5.4Application Setup (18)
6INTEGRATOR HINTS (19)
6.1How to begin (19)
6.2Flow control (20)
6.3Blocking command (20)
6.4Lookup table for FCS calculation (21)
6.5Ignored command (22)
7AT Commands (23)
8Document Change Log (24)
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 1 INTRODUCTION
1.1 Scope of document
The scope of the present document is to describe a multiplexing protocol implemented in the Telit module. The multiplexing protocol can be used to send any data, SMS, fax, TCP data.
NOTE: CUMX can be activated only with the interface SELINT 2; this means that for the modules GM862-QUAD/PY and GE863-QUAD/PY which start as default in SELINT 0 or SELINT 11, before activating CMUX, interface should be changed to SELINT 2.
1 please consult AT Commands Reference Guide 80000ST10025a for more information
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 2 APPLICABLE DOCUMENTS
? Digital Cellular Telecommunications Systems (Phase 2+); Terminal Equipment to Mobile Station (TE-MS) "Multiplexer Protocol"; ETSI TS 101 369 V7.1.0 (1999-11), GSM 07.10 Version 7.1.0, Release 199
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 3 TECHNICAL CHARACTERISTICS
3.1 Product architecture
The Multiplexer mode enables one serial interface to transmit data to four different customer applications. This is achieved by providing four virtual channels using a Multiplexer (Mux).
This is especially advantageous when a fax/data/GPRS call is ongoing. Using the Multiplexer features, e.g. controlling the module or using the SMS service can be done via the additional channels without disturbing the data flow; access to the second UART is not necessary.
Furthermore, several accesses to the module can be created with the Multiplexer. This is of great advantage when several independent electronic devices or interfaces are used.
To access the three virtual interfaces, both the GSM engine and the customer application must contain Mux components, which communicate over the multiplexer protocol.
In Multiplexer mode, AT commands and data are encapsulated into packets. Each packet has channel identification and may vary in length.
3.2 Implementation feature and limitation
? 7.10 CMUX Basic Option used
? CMUX implementation support four full DLCI (Serial Port)
? CMUX can operate only at Fixed rate, if AT+CMUX is sent with IPR=0 an Error is returned, with a maximum rate of 115200
? Every instance has its own user profile storage in NVM
? Independent setting of unsolicited message.
? In case of GPS product one serial port can be dedicated to NMEA output.
? Every Instance has its own independent flow control.
3.3 AT command interface interactions
The following AT commands would modify the global operation of the system, independently from the CMUX instance that is using them.
? AT#HFMICG
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 ? AT#HSMICG
? AT+CMUT
? AT#STM
? AT#SHFEC
? AT#CAP
? AT+CLVL
? AT#SRS
? AT+CRSL
? AT#SRP
? AT#NITZ
? AT+CALM
? AT#SHFSD
? AT#DAC
? AT+CFUN
? AT+COPS
The AT commands that require to modify a setting would be saved in a global profile. They would be reloaded at boot time with relation to the ATY1, ATY0 previously issued on the instance CMUX1 or ASC0.
When in multiplexed mode it is suggested not to used the +CFUN command but the PSC (Power saving command) described by GSM 7.10 specification.
CMUX User Guide 30268ST10299A Rev. 0 - 13/10/06
4 SERIAL MULTIPLEXER PROTOCOL 4.1 CMUX Frame Structure
All information transmitted between the module and the application is based on frame that have the following frame Structure
Flag Address Control Length
Indicator
Information FCS Flag
1 octet 1 octet 1 octet 1or
2 octets Unspecified length
but integral number
of octets
1 octet 1 octet
Flag Octet
Each frame begins and ends with a flag octet define as ( binary:11111001 or hexadecimal 0xF9)
Address Octet
Is formatted as follow:
0 1 2 3 4 5 6 7
EA C/R D L C I
EA: Extension Bit
Shall be always 1 in the basic option of the protocol
C/R: Command Response
The C/R (command/response) bit identifies the frame as either a command or a response. In conformance with the standard HDLC rules, a command frame contains the address of the data link connection entity to which it is transmitted while a response frame contains the address of the data link connection entity transmitting the frame.
Command/response Direction C/R value
Command Application ??→Module 1
Module ??→Application 0 Response Application ??→Module 0
Module ??→Application 1
CMUX User Guide 30268ST10299A Rev. 0 - 13/10/06
Example:
Application take the initiative to initialize the multiplexer (i.e. sends the SABM command at DLCI 0 ) and the Module that accepts the initialization of the multiplexer (i.e. sends the UA response at DLCI 0) DLCI: Data Link Connection Identifier
DLCI value identify the Virtual Port inside the Module with the following assignment
DLCI
0 Reserved to Control Channel
1 Virtual Port #1
2 Virtual Port #2
3 Virtual Port #3
4 Reserved for Python debug
Control Field
The content of the control field defines the type of frame
Frame Type 0 1 2 3 4 5 6 7
SABM (Set Asynchronous
Balanced Mode)
1 1 1 1 P/F 1 0 0
UA (Unnumbered
Acknowledgement)
1 1 0 0 P/F 1 1 0
DM (Disconnected Mode) 1 1 1 1 P/F 0 0 0
DISC (Disconnect) 1 1 0 0 P/F 0 1 0
UIH (Unnumbered
Information with Header
check)
1 1 1 1 P/F 1 1 1
P/F is the Poll/Final bit:
Commands: P=1
Response: F=1
SABM (Set Asynchronous Balanced Mode )
The SABM command shall be used by the application to start the HDLC Connection.
The module will answer to this command with an UA Frame.
UA (Unnumbered Acknowledgement)
The UA response is sent by the module to inform that a SABM or DISC command was accepted
DM (Disconnected Mode)
The DM response is sent by the module to inform that a SABM or DISC command was rejected, this can happens if for example a SABM is sent for a DLCI not supported. Or if a DISC is sent to a DLCI Address already closed.
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 DISC (Disconnect)
The DISC is used to close a previous established connection. If the application send a disc for the DLCI 0 (the control channel), all the established channel will be closed.
The module will answer to this command with an UA Frame.
UIH (Unnumbered Information)
Refer to the specific chapter
Length Indicator
This Octet specified the length of the information field
0 1 2 3 4 5 6 7
E/A L1 L2 L3 L4 L5 L6 L7
E/A Bit shall be 1 if 7 bit are enough for the len ( len <= 127) otherwise len
Shall be coded with two octet
Octet 1
0 1 2 3 4 5 6 7
0 L1 L2 L3 L4 L5 L6 L7
Octet 2
0 1 2 3 4 5 6 7
1 L9 L10 L11 L1
2 L1
3 L1
4 L15
Information Data
The information field is the payload of the frame and carries the user data. The field exist only for frame type that contains UIH Control Field.
The P/F bit shall be set to 0 when sending this field.
FCS ( Frame Checking Sequence)
The FCS is calculated over all the frame with the exclusion of the flags. Only in case of UIH frame the FCS shall not be calculated over the information field.
The FCS shall be the ones complement of the sum (modulo 2) of
the remainder of xk (x7 + x6 + x5 + x4 + x3 + x2 + x1 + 1)
divided (modulo 2) by the generator polynomial x8 + x2 + x + 1,
where k is the number of bits in the frame
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 4.2 UIH Control Channel Frame Coding
DLCI shall be always 0
Value
Type Length
Indicator
1 octet 1or
2 octets n Octet
Type Octet:
0 1 2 3 4 5 6 7
EA C/R T Y P E
EA: Extension Bit
Shall be always 1.
C/R: Identify if is a Command or Response
Length indicator
Is code like in the Cmux Frame Structure
Value
The number of octet are specified by the Length Indicator and depend on the type of the command as follow:
Multiplexer close down (CLD)
The multiplexer close down command is used to reset the link into normal AT command mode without multiplexing
Type Len
3 0
Test Command (Test)
The test command is used to test the connection between MS and the TE. The length byte describes the number of values bytes, which are used as a verification pattern. The opposite entity shall respond with exactly the same value bytes.
Type Len Value 1 Value2 Value .. Value N
4 N Any Char Any Char Any Char Any Char
Modem Status Command (MSC)
This command is used to send V.24 signal info.
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 Format without break indication
Type Len Value 1 Value 2
6 2 DLCI V24 Octet
Format with Break Indication
Type Len Value 1 Value 2 Value 3
6 3 DLCI V24 Octet Break
Octet
V24 Octet from Module to Application
0 1 2 3 4 5 6 7
1 FC DSR CTS 0 0 RIN
DCD
G
V24 Octet from Application to Module
0 1 2 3 4 5 6 7
1 FC DTR RTS 0 0 0 0
Break Octet
0 1 2 3 4 5 6 7
1 0 0 0 0 0 0 0
This octet shall be sent every time a Break signal shall be simulated
Non Supported Command Response (NSC)
This response is sent whenever a command type is not supported by the receiving entity.
Type Len Value 1
8 1 Command Not
Supported
Power Saving Control (PSC)
This command is used to program the power saving mode of the module when Multiplexer mode.
AT+CFUN command shall not be used.
Type Len Value 1
6 1 Power Saving Mode
Power Saving Mode: TBD
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 4.3 UIH Data Channel Frame Coding
DLCI shall be 1,2,3 or 4
Length Indicator User Data
1or2 octets n Octet
Type Octet:
0 1 2 3 4 5 6 7
EA C/R T Y P E
EA: Extension Bit
Shall always be 1.
C/R: Identify if is a Command or Response
Length indicator
Is code like in the Cmux Frame Structure
User Data
The Number of data is defined by the Len Indicator
CMUX User Guide 30268ST10299A Rev. 0 - 13/10/06
4.4 CMUX establishment scenario
CMUX User Guide 30268ST10299A Rev. 0 - 13/10/06
5 TELIT SERIAL PORT PC INTERFACE FOR CMUX
5.1 Interface Specification
To exploit the capabilities of CMUX, Telit developed a tool called Telit Serial Port MUX. It is a PC interface able to manage data coming/to be sent from/to CMUX. This target is achieved creating up to four serial virtual port on the PC and using a specific communication protocol to manage the communication between the real serial COM, changing data with CMUX, and each of the virtual port. 5.2 Scenario
As you can see, you can run 3 different applications using the same CMUX module, for example 3 HyperTerminal sending commands at the same time to the same module.
CMUX
C
O
M
Virtual COM 1
Virtual COM 2
Virtual COM 3
Python debug
PC TOOL 1
PC TOOL 2
PC TOOL 3
PC TOOL 4
P
C MODULE
CMUX User Guide 30268ST10299A Rev. 0 - 13/10/06
5.3 Graphical Interface
Telit Serial Port Mux application on your PC after installation looks like in the following figure:
? Modem Port Panel: here you can find the information about the modem connected to your PC, like:
1. COM on your PC used to transfer data, selected during the initial setup or selecting the
Setup voice in the application menu.
2. COM Speed selected.
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06
3. Connection Status: it can be “idle” or “error” when CMUX is disconnected, “connecting”
when PC is trying to connect to CMUX and “connected” when CMUX is connected
successfully.
4. Indication about the model of the modem connected.
? Virtual Port Panel: here you can find all the information about the connection using a Virtual Com installed on your PC:
1. Virtual Com number.
2. Virtual Port Status: it can be “idle”, “idle no DCD”, “Error”, “Opened”.
3. Baud Rate.
4. Number of bytes received and transmitted (RX Bytes, TX Bytes).
5. All the common serial port signals like RequestToSend, DataTerminalReady,
ClearToSend, DataCarrierDetected, DataSetReady and RingIndicator.
? Tray Icon: there is a Tray Icon indicating the status of the Serial Port Mux:
1. CMUX connected: the Tray Icon is blinking.
2. CMUX disconnected or connecting.
3. CMUX error.
CMUX User Guide 30268ST10299A Rev. 0 - 13/10/06
5.4 Application Setup
The selection of the number of Virtual ports to be created, like the selection of the real COM to be used and its speed is made in the setup section. There are two possibilities to do this, during the tool installation and when the tool is running.
Virtual Ports created are visible also on the Device Manager:
Module Serial Port Panel:
here you can select the Real COM to
use and its speed
Virtual Serial Port Panel:
here you can create virtual ports
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 6 INTEGRATOR HINTS
6.1 How to begin
The customer/integrator in order to design its own Multiplexer application must follow these basic requirements:
? The GSM engine supports the basic option and UIH Framing according to GSM 07.10;
? Character framing must be configured for 8 data bits, no parity and 1 stop bit;
? Hardware flow control is recommended for use with multiplexer mode. If used, it needs to be set before Multiplexer mode is entered;
If the GSM engine is operated in multiplexer mode, the following restrictions apply: ? MO and MT circuit-switched data and fax calls are available on any channels;
? Multiplex mode cannot be started while autobauding (AT+IPR=0) is enabled;
? XON/OFF flow control is not supported in multiplexer mode.
When using the following functions, be aware of possible dependencies between the different channels. One way of avoiding problems may be to dedicate certain commands/features to one of the channels or to assure that the application avoids conflicts.
? Call control: a voice call can be initiated, answered on any channel and closed only on the initialized channel;
? Phonebook access: if you wish to write the same phonebook entry on two or more different channels at the same time, please note that the only the last entry will be stored;
The following functions or events may be ongoing independently on different channels: ? Unsolicited Result Codes (URCs) will generally be transmitted to all logical channels with the dependency on the issued AT+CNMI;
? Single quality and cell information can be retrieved on a single channel;
? Profile configuration commands can be issued and retrieved on any channel, no matter on which the command is executed.
CMUX User Guide
30268ST10299A Rev. 0 - 13/10/06 6.2 Flow control
The internal logical flow control represents the existing flow control to the module. For example, if a data call is initiated and the customer application transmits data to the module on this channel, the module will stop the data transmission from time to time. This happens because the module operates with a bandwidth of 9k6 on air, but the customer application uses a larger width. In this case the module sends a MSC message with FC-BIT set. After all data stored in the internal buffer have been sent, the module will send a second MSC message with FC-BIT reset. As already pointed out, the logical flow control operates like RTS/CTS but with FC-BIT on every channel. The RTS/CTS are not used for flow control because the traffic on the logical channels may cause a temporary loss of bandwidth on another channel. This behavior has no impact on the handshake V.24 lines.
Hardware flow control is recommended for use with multiplexer.
The customer application decodes and encodes the data. To prevent loss of data, the application must be able process the information about internal flow control (MSC) regulated by the module. Flow control information is transmitted within the data flow and contains messages whether or not the channel is allowed to send. As of Multiplexer Protocol, the customer application must set RTS (in the direction to the module) on channel 1. RTS shall not be switched off to prevent loss of data (control data cannot be sent in this case). If flow control is needed, it is recommended to use logical flow control on every channel.
6.3 Blocking command
With the first versions of the CMUX implementation some AT command will frieze execution of other command on the other instance until they complete. Executions of the freeze command restart automatically.
The list of command is:
? ATA
? ATD
? ATO
? ATH
? AT#CAMEN
? AT#TPHOTO
? AT+CGATT
? AT+CGACT
? AT+COPS
? AT+CREG
? AT#SEMAIL
? AT#EMAILD
? AT#SKTOP
? AT#SKTD