1============================== 2GSM 0710 tty multiplexor HOWTO 3============================== 4 5.. contents:: :local: 6 7This line discipline implements the GSM 07.10 multiplexing protocol 8detailed in the following 3GPP document: 9 10 https://www.3gpp.org/ftp/Specs/archive/07_series/07.10/0710-720.zip 11 12This document give some hints on how to use this driver with GPRS and 3G 13modems connected to a physical serial port. 14 15How to use it 16============= 17 18Config Initiator 19---------------- 20 21#. Initialize the modem in 0710 mux mode (usually ``AT+CMUX=`` command) through 22 its serial port. Depending on the modem used, you can pass more or less 23 parameters to this command. 24 25#. Switch the serial line to using the n_gsm line discipline by using 26 ``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 program 37 (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 B115200 45 #define SERIAL_PORT /dev/ttyS0 46 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 mode 60 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 before 64 being able to answer to the first MUX packet so a delay 65 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 multiplexing 112 mode. This may prevent a successful re-opening of the port later. To avoid 113 this situation either reset the modem if your hardware allows that or send 114 a disconnect command frame manually before initializing the multiplexing mode 115 for the second time. The byte sequence for the disconnect command frame is:: 116 117 0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9 118 119Config Requester 120---------------- 121 122#. Receive ``AT+CMUX=`` command through its serial port, initialize mux mode 123 config. 124 125#. Switch the serial line to using the *n_gsm* line discipline by using 126 ``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 B115200 142 #define SERIAL_PORT /dev/ttyS0 143 144 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