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100 lines
3.5 KiB
100 lines
3.5 KiB
============================== |
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GSM 0710 tty multiplexor HOWTO |
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============================== |
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This line discipline implements the GSM 07.10 multiplexing protocol |
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detailed in the following 3GPP document: |
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https://www.3gpp.org/ftp/Specs/archive/07_series/07.10/0710-720.zip |
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This document give some hints on how to use this driver with GPRS and 3G |
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modems connected to a physical serial port. |
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How to use it |
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------------- |
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1. initialize the modem in 0710 mux mode (usually AT+CMUX= command) through |
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its serial port. Depending on the modem used, you can pass more or less |
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parameters to this command, |
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2. switch the serial line to using the n_gsm line discipline by using |
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TIOCSETD ioctl, |
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3. configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl, |
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4. obtain base gsmtty number for the used serial port, |
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Major parts of the initialization program : |
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(a good starting point is util-linux-ng/sys-utils/ldattach.c):: |
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#include <stdio.h> |
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#include <stdint.h> |
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#include <linux/gsmmux.h> |
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#include <linux/tty.h> |
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#define DEFAULT_SPEED B115200 |
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#define SERIAL_PORT /dev/ttyS0 |
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int ldisc = N_GSM0710; |
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struct gsm_config c; |
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struct termios configuration; |
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uint32_t first; |
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/* open the serial port connected to the modem */ |
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fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY); |
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/* configure the serial port : speed, flow control ... */ |
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/* send the AT commands to switch the modem to CMUX mode |
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and check that it's successful (should return OK) */ |
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write(fd, "AT+CMUX=0\r", 10); |
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/* experience showed that some modems need some time before |
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being able to answer to the first MUX packet so a delay |
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may be needed here in some case */ |
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sleep(3); |
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/* use n_gsm line discipline */ |
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ioctl(fd, TIOCSETD, &ldisc); |
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/* get n_gsm configuration */ |
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ioctl(fd, GSMIOC_GETCONF, &c); |
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/* we are initiator and need encoding 0 (basic) */ |
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c.initiator = 1; |
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c.encapsulation = 0; |
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/* our modem defaults to a maximum size of 127 bytes */ |
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c.mru = 127; |
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c.mtu = 127; |
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/* set the new configuration */ |
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ioctl(fd, GSMIOC_SETCONF, &c); |
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/* get first gsmtty device node */ |
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ioctl(fd, GSMIOC_GETFIRST, &first); |
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printf("first muxed line: /dev/gsmtty%i\n", first); |
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/* and wait for ever to keep the line discipline enabled */ |
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daemon(0,0); |
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pause(); |
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5. use these devices as plain serial ports. |
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for example, it's possible: |
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- and to use gnokii to send / receive SMS on ttygsm1 |
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- to use ppp to establish a datalink on ttygsm2 |
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6. first close all virtual ports before closing the physical port. |
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Note that after closing the physical port the modem is still in multiplexing |
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mode. This may prevent a successful re-opening of the port later. To avoid |
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this situation either reset the modem if your hardware allows that or send |
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a disconnect command frame manually before initializing the multiplexing mode |
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for the second time. The byte sequence for the disconnect command frame is:: |
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0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9. |
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Additional Documentation |
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------------------------ |
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More practical details on the protocol and how it's supported by industrial |
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modems can be found in the following documents : |
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- http://www.telit.com/module/infopool/download.php?id=616 |
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- http://www.u-blox.com/images/downloads/Product_Docs/LEON-G100-G200-MuxImplementation_ApplicationNote_%28GSM%20G1-CS-10002%29.pdf |
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- http://www.sierrawireless.com/Support/Downloads/AirPrime/WMP_Series/~/media/Support_Downloads/AirPrime/Application_notes/CMUX_Feature_Application_Note-Rev004.ashx |
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- http://wm.sim.com/sim/News/photo/2010721161442.pdf |
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11-03-08 - Eric Bénard - <[email protected]>
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