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1==============================2GSM 0710 tty multiplexor HOWTO3==============================4 5.. contents:: :local:6 7This line discipline implements the GSM 07.10 multiplexing protocol8detailed in the following 3GPP document:9 10 https://www.3gpp.org/ftp/Specs/archive/07_series/07.10/0710-720.zip11 12This document give some hints on how to use this driver with GPRS and 3G13modems connected to a physical serial port.14 15How to use it16=============17 18Config Initiator19----------------20 21#. Initialize the modem in 0710 mux mode (usually ``AT+CMUX=`` command) through22 its serial port. Depending on the modem used, you can pass more or less23 parameters to this command.24 25#. Switch the serial line to using the n_gsm line discipline by using26 ``TIOCSETD`` ioctl.27 28#. Configure the mux using ``GSMIOC_GETCONF_EXT``/``GSMIOC_SETCONF_EXT`` ioctl if needed.29 30#. Configure the mux using ``GSMIOC_GETCONF``/``GSMIOC_SETCONF`` ioctl.31 32#. Configure DLCs using ``GSMIOC_GETCONF_DLCI``/``GSMIOC_SETCONF_DLCI`` ioctl for non-defaults.33 34#. Obtain base gsmtty number for the used serial port.35 36 Major parts of the initialization program37 (a good starting point is util-linux-ng/sys-utils/ldattach.c)::38 39 #include <stdio.h>40 #include <stdint.h>41 #include <linux/gsmmux.h>42 #include <linux/tty.h>43 44 #define DEFAULT_SPEED B11520045 #define SERIAL_PORT /dev/ttyS046 47 int ldisc = N_GSM0710;48 struct gsm_config c;49 struct gsm_config_ext ce;50 struct gsm_dlci_config dc;51 struct termios configuration;52 uint32_t first;53 54 /* open the serial port connected to the modem */55 fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);56 57 /* configure the serial port : speed, flow control ... */58 59 /* send the AT commands to switch the modem to CMUX mode60 and check that it's successful (should return OK) */61 write(fd, "AT+CMUX=0\r", 10);62 63 /* experience showed that some modems need some time before64 being able to answer to the first MUX packet so a delay65 may be needed here in some case */66 sleep(3);67 68 /* use n_gsm line discipline */69 ioctl(fd, TIOCSETD, &ldisc);70 71 /* get n_gsm extended configuration */72 ioctl(fd, GSMIOC_GETCONF_EXT, &ce);73 /* use keep-alive once every 5s for modem connection supervision */74 ce.keep_alive = 500;75 /* set the new extended configuration */76 ioctl(fd, GSMIOC_SETCONF_EXT, &ce);77 /* get n_gsm configuration */78 ioctl(fd, GSMIOC_GETCONF, &c);79 /* we are initiator and need encoding 0 (basic) */80 c.initiator = 1;81 c.encapsulation = 0;82 /* our modem defaults to a maximum size of 127 bytes */83 c.mru = 127;84 c.mtu = 127;85 /* set the new configuration */86 ioctl(fd, GSMIOC_SETCONF, &c);87 /* get DLC 1 configuration */88 dc.channel = 1;89 ioctl(fd, GSMIOC_GETCONF_DLCI, &dc);90 /* the first user channel gets a higher priority */91 dc.priority = 1;92 /* set the new DLC 1 specific configuration */93 ioctl(fd, GSMIOC_SETCONF_DLCI, &dc);94 /* get first gsmtty device node */95 ioctl(fd, GSMIOC_GETFIRST, &first);96 printf("first muxed line: /dev/gsmtty%i\n", first);97 98 /* and wait for ever to keep the line discipline enabled */99 daemon(0,0);100 pause();101 102#. Use these devices as plain serial ports.103 104 For example, it's possible:105 106 - to use *gnokii* to send / receive SMS on ``ttygsm1``107 - to use *ppp* to establish a datalink on ``ttygsm2``108 109#. First close all virtual ports before closing the physical port.110 111 Note that after closing the physical port the modem is still in multiplexing112 mode. This may prevent a successful re-opening of the port later. To avoid113 this situation either reset the modem if your hardware allows that or send114 a disconnect command frame manually before initializing the multiplexing mode115 for the second time. The byte sequence for the disconnect command frame is::116 117 0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9118 119Config Requester120----------------121 122#. Receive ``AT+CMUX=`` command through its serial port, initialize mux mode123 config.124 125#. Switch the serial line to using the *n_gsm* line discipline by using126 ``TIOCSETD`` ioctl.127 128#. Configure the mux using ``GSMIOC_GETCONF_EXT``/``GSMIOC_SETCONF_EXT``129 ioctl if needed.130 131#. Configure the mux using ``GSMIOC_GETCONF``/``GSMIOC_SETCONF`` ioctl.132 133#. Configure DLCs using ``GSMIOC_GETCONF_DLCI``/``GSMIOC_SETCONF_DLCI`` ioctl for non-defaults.134 135#. Obtain base gsmtty number for the used serial port::136 137 #include <stdio.h>138 #include <stdint.h>139 #include <linux/gsmmux.h>140 #include <linux/tty.h>141 #define DEFAULT_SPEED B115200142 #define SERIAL_PORT /dev/ttyS0143 144 int ldisc = N_GSM0710;145 struct gsm_config c;146 struct gsm_config_ext ce;147 struct gsm_dlci_config dc;148 struct termios configuration;149 uint32_t first;150 151 /* open the serial port */152 fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);153 154 /* configure the serial port : speed, flow control ... */155 156 /* get serial data and check "AT+CMUX=command" parameter ... */157 158 /* use n_gsm line discipline */159 ioctl(fd, TIOCSETD, &ldisc);160 161 /* get n_gsm extended configuration */162 ioctl(fd, GSMIOC_GETCONF_EXT, &ce);163 /* use keep-alive once every 5s for peer connection supervision */164 ce.keep_alive = 500;165 /* set the new extended configuration */166 ioctl(fd, GSMIOC_SETCONF_EXT, &ce);167 /* get n_gsm configuration */168 ioctl(fd, GSMIOC_GETCONF, &c);169 /* we are requester and need encoding 0 (basic) */170 c.initiator = 0;171 c.encapsulation = 0;172 /* our modem defaults to a maximum size of 127 bytes */173 c.mru = 127;174 c.mtu = 127;175 /* set the new configuration */176 ioctl(fd, GSMIOC_SETCONF, &c);177 /* get DLC 1 configuration */178 dc.channel = 1;179 ioctl(fd, GSMIOC_GETCONF_DLCI, &dc);180 /* the first user channel gets a higher priority */181 dc.priority = 1;182 /* set the new DLC 1 specific configuration */183 ioctl(fd, GSMIOC_SETCONF_DLCI, &dc);184 /* get first gsmtty device node */185 ioctl(fd, GSMIOC_GETFIRST, &first);186 printf("first muxed line: /dev/gsmtty%i\n", first);187 188 /* and wait for ever to keep the line discipline enabled */189 daemon(0,0);190 pause();191 19211-03-08 - Eric Bénard - <eric@eukrea.com>193