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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>