Commit | Line | Data |
---|---|---|
f1374017 MCC |
1 | ============================== |
2 | GSM 0710 tty multiplexor HOWTO | |
3 | ============================== | |
4 | ||
5 | This line discipline implements the GSM 07.10 multiplexing protocol | |
6 | detailed in the following 3GPP document: | |
7 | ||
8 | http://www.3gpp.org/ftp/Specs/archive/07_series/07.10/0710-720.zip | |
9 | ||
10 | This document give some hints on how to use this driver with GPRS and 3G | |
11 | modems connected to a physical serial port. | |
12 | ||
13 | How to use it | |
14 | ------------- | |
15 | 1. initialize the modem in 0710 mux mode (usually AT+CMUX= command) through | |
16 | its serial port. Depending on the modem used, you can pass more or less | |
17 | parameters to this command, | |
18 | 2. switch the serial line to using the n_gsm line discipline by using | |
19 | TIOCSETD ioctl, | |
20 | 3. configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl, | |
21 | ||
22 | Major parts of the initialization program : | |
23 | (a good starting point is util-linux-ng/sys-utils/ldattach.c):: | |
24 | ||
25 | #include <linux/gsmmux.h> | |
26 | #define N_GSM0710 21 /* GSM 0710 Mux */ | |
27 | #define DEFAULT_SPEED B115200 | |
28 | #define SERIAL_PORT /dev/ttyS0 | |
29 | ||
30 | int ldisc = N_GSM0710; | |
31 | struct gsm_config c; | |
32 | struct termios configuration; | |
33 | ||
34 | /* open the serial port connected to the modem */ | |
35 | fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY); | |
36 | ||
37 | /* configure the serial port : speed, flow control ... */ | |
38 | ||
39 | /* send the AT commands to switch the modem to CMUX mode | |
40 | and check that it's successful (should return OK) */ | |
41 | write(fd, "AT+CMUX=0\r", 10); | |
42 | ||
43 | /* experience showed that some modems need some time before | |
44 | being able to answer to the first MUX packet so a delay | |
45 | may be needed here in some case */ | |
46 | sleep(3); | |
47 | ||
48 | /* use n_gsm line discipline */ | |
49 | ioctl(fd, TIOCSETD, &ldisc); | |
50 | ||
51 | /* get n_gsm configuration */ | |
52 | ioctl(fd, GSMIOC_GETCONF, &c); | |
53 | /* we are initiator and need encoding 0 (basic) */ | |
54 | c.initiator = 1; | |
55 | c.encapsulation = 0; | |
56 | /* our modem defaults to a maximum size of 127 bytes */ | |
57 | c.mru = 127; | |
58 | c.mtu = 127; | |
59 | /* set the new configuration */ | |
60 | ioctl(fd, GSMIOC_SETCONF, &c); | |
61 | ||
62 | /* and wait for ever to keep the line discipline enabled */ | |
63 | daemon(0,0); | |
64 | pause(); | |
65 | ||
66 | 4. create the devices corresponding to the "virtual" serial ports (take care, | |
67 | each modem has its configuration and some DLC have dedicated functions, | |
68 | for example GPS), starting with minor 1 (DLC0 is reserved for the management | |
69 | of the mux):: | |
70 | ||
71 | MAJOR=`cat /proc/devices |grep gsmtty | awk '{print $1}` | |
72 | for i in `seq 1 4`; do | |
73 | mknod /dev/ttygsm$i c $MAJOR $i | |
74 | done | |
75 | ||
76 | 5. use these devices as plain serial ports. | |
77 | ||
78 | for example, it's possible: | |
79 | ||
80 | - and to use gnokii to send / receive SMS on ttygsm1 | |
81 | - to use ppp to establish a datalink on ttygsm2 | |
82 | ||
83 | 6. first close all virtual ports before closing the physical port. | |
84 | ||
85 | Note that after closing the physical port the modem is still in multiplexing | |
86 | mode. This may prevent a successful re-opening of the port later. To avoid | |
87 | this situation either reset the modem if your hardware allows that or send | |
88 | a disconnect command frame manually before initializing the multiplexing mode | |
89 | for the second time. The byte sequence for the disconnect command frame is:: | |
90 | ||
91 | 0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9. | |
92 | ||
93 | Additional Documentation | |
94 | ------------------------ | |
95 | More practical details on the protocol and how it's supported by industrial | |
96 | modems can be found in the following documents : | |
97 | ||
98 | - http://www.telit.com/module/infopool/download.php?id=616 | |
99 | - http://www.u-blox.com/images/downloads/Product_Docs/LEON-G100-G200-MuxImplementation_ApplicationNote_%28GSM%20G1-CS-10002%29.pdf | |
100 | - http://www.sierrawireless.com/Support/Downloads/AirPrime/WMP_Series/~/media/Support_Downloads/AirPrime/Application_notes/CMUX_Feature_Application_Note-Rev004.ashx | |
101 | - http://wm.sim.com/sim/News/photo/2010721161442.pdf | |
102 | ||
103 | 11-03-08 - Eric BĂ©nard - <eric@eukrea.com> |