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author | Eric Bénard <eric@eukrea.com> | 2011-03-09 19:24:48 +0100 |
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committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-03-09 15:43:38 -0800 |
commit | 323e84122ec6447a5a18de42b0dc7114f77e76c4 (patch) | |
tree | b1ee88763495b491df28e2d7c1a9d26929586e79 /Documentation/serial/n_gsm.txt | |
parent | 550462378515a82279e07f12e2c105f617f112f8 (diff) | |
download | linux-stable-323e84122ec6447a5a18de42b0dc7114f77e76c4.tar.gz linux-stable-323e84122ec6447a5a18de42b0dc7114f77e76c4.tar.bz2 linux-stable-323e84122ec6447a5a18de42b0dc7114f77e76c4.zip |
n_gsm: add a documentation
* this documentation gives some details on how to get the n_gsm
line discipline to work with modems supporting 07.10 basic option.
* it was tested on Telit and Simcom modems.
Signed-off-by: Eric Bénard <eric@eukrea.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation/serial/n_gsm.txt')
-rw-r--r-- | Documentation/serial/n_gsm.txt | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/Documentation/serial/n_gsm.txt b/Documentation/serial/n_gsm.txt new file mode 100644 index 000000000000..397f41a1f153 --- /dev/null +++ b/Documentation/serial/n_gsm.txt @@ -0,0 +1,89 @@ +n_gsm.c GSM 0710 tty multiplexor HOWTO +=================================================== + +This line discipline implements the GSM 07.10 multiplexing protocol +detailed in the following 3GPP document : +http://www.3gpp.org/ftp/Specs/archive/07_series/07.10/0710-720.zip + +This document give some hints on how to use this driver with GPRS and 3G +modems connected to a physical serial port. + +How to use it +------------- +1- initialize the modem in 0710 mux mode (usually AT+CMUX= command) through +its serial port. Depending on the modem used, you can pass more or less +parameters to this command, +2- switch the serial line to using the n_gsm line discipline by using +TIOCSETD ioctl, +3- configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl, + +Major parts of the initialization program : +(a good starting point is util-linux-ng/sys-utils/ldattach.c) +#include <linux/gsmmux.h> +#define N_GSM0710 21 /* GSM 0710 Mux */ +#define DEFAULT_SPEED B115200 +#define SERIAL_PORT /dev/ttyS0 + + int ldisc = N_GSM0710; + struct gsm_config c; + struct termios configuration; + + /* open the serial port connected to the modem */ + fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY); + + /* configure the serial port : speed, flow control ... */ + + /* send the AT commands to switch the modem to CMUX mode + and check that it's succesful (should return OK) */ + write(fd, "AT+CMUX=0\r", 10); + + /* experience showed that some modems need some time before + being able to answer to the first MUX packet so a delay + may be needed here in some case */ + sleep(3); + + /* use n_gsm line discipline */ + ioctl(fd, TIOCSETD, &ldisc); + + /* get n_gsm configuration */ + ioctl(fd, GSMIOC_GETCONF, &c); + /* we are initiator and need encoding 0 (basic) */ + c.initiator = 1; + c.encapsulation = 0; + /* our modem defaults to a maximum size of 127 bytes */ + c.mru = 127; + c.mtu = 127; + /* set the new configuration */ + ioctl(fd, GSMIOC_SETCONF, &c); + + /* and wait for ever to keep the line discipline enabled */ + daemon(0,0); + pause(); + +4- create the devices corresponding to the "virtual" serial ports (take care, +each modem has its configuration and some DLC have dedicated functions, +for example GPS), starting with minor 1 (DLC0 is reserved for the management +of the mux) + +MAJOR=`cat /proc/devices |grep gsmtty | awk '{print $1}` +for i in `seq 1 4`; do + mknod /dev/ttygsm$i c $MAJOR $i +done + +5- use these devices as plain serial ports. +for example, it's possible : +- and to use gnokii to send / receive SMS on ttygsm1 +- to use ppp to establish a datalink on ttygsm2 + +6- first close all virtual ports before closing the physical port. + +Additional Documentation +------------------------ +More practical details on the protocol and how it's supported by industrial +modems can be found in the following documents : +http://www.telit.com/module/infopool/download.php?id=616 +http://www.u-blox.com/images/downloads/Product_Docs/LEON-G100-G200-MuxImplementation_ApplicationNote_%28GSM%20G1-CS-10002%29.pdf +http://www.sierrawireless.com/Support/Downloads/AirPrime/WMP_Series/~/media/Support_Downloads/AirPrime/Application_notes/CMUX_Feature_Application_Note-Rev004.ashx +http://wm.sim.com/sim/News/photo/2010721161442.pdf + +11-03-08 - Eric Bénard - <eric@eukrea.com> |