[General] how to reset multiplexing (CMUX) on sim800

[robert@redcor.ch]

Hi there,

I am using i sligthly modified c program I found on the net:

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Code C - [expand]
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/**
* Cmux
* Enables GSM 0710 multiplex using n_gsm
*
* Copyright (C) 2013 - Rtone - Nicolas Le Manchet <nicolaslm@rtone.fr>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <termios.h>
#include <net/if.h>
#include <linux/types.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <err.h>
#include <signal.h>
/**
* gsmmux.h provides n_gsm line dicipline structures and functions.
* It should be kept in sync with your kernel release.
*/
#include "gsmmux.h"
/* n_gsm ioctl */
#ifndef N_GSM0710
# define N_GSM0710  21
#endif
/* attach a line discipline ioctl */
#ifndef TIOCSETD
# define TIOCSETD   0x5423
#endif
/* serial port of the modem */
#define SERIAL_PORT "/dev/ttyS1"
/* line speed */
#define LINE_SPEED  B115200
/* maximum transfert unit (MTU), value in bytes */
#define MTU 512
/**
* whether or not to create virtual TTYs for the multiplex
* 0 : do not create
* 1 : create
*/
#define CREATE_NODES    1
/* number of virtual TTYs to create (most modems can handle up to 4) */
#define NUM_NODES   4
/* name of the virtual TTYs to create */
#define BASENAME_NODES  "/dev/ttyGSM"
/* name of the driver, used to get the major number */
#define DRIVER_NAME "gsmtty"
/**
* whether or not to print debug messages to stderr
* 0 : debug off
* 1 : debug on
*/
#define DEBUG   1
/**
* whether or not to detach the program from the terminal
* 0 : do not daemonize
* 1 : daemonize
*/
#define DAEMONIZE   1
/* size of the reception buffer which gets data from the serial line */
#define SIZE_BUF    256
/**
* Prints debug messages to stderr if debug is wanted
*/
static void dbg(char *fmt, ...) {
va_list args;
if (DEBUG) {
fflush(NULL);
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
fprintf(stderr, "\n");
fflush(NULL);
}
return;
}
/**
* Sends an AT command to the specified line and gets its result
* Returns 0 on success
* -1 on failure
*/
int send_at_command(int serial_fd, char *command) {
char buf[SIZE_BUF];
int r;
/* write the AT command to the serial line */
if (write(serial_fd, command, strlen(command)) <= 0)
err(EXIT_FAILURE, "Cannot write to %s", SERIAL_PORT);
/* wait a bit to allow the modem to rest */
sleep(1);
/* read the result of the command from the modem */
memset(buf, 0, sizeof(buf));
r = read(serial_fd, buf, sizeof(buf));
if (r == -1)
err(EXIT_FAILURE, "Cannot read %s", SERIAL_PORT);
/* if there is no result from the modem, return failure */
if (r == 0) {
dbg("%s\t: No response", command);
return -1;
}
/* if we have a result and want debug info, strip CR & LF out from the output */
if (DEBUG) {
int i;
char bufp[SIZE_BUF];
memcpy(bufp, buf, sizeof(buf));
for(i=0; i<strlen(bufp); i++) {
if (bufp[i] == '\r' || bufp[i] == '\n')
bufp[i] = ' ';
}
dbg("%s\t: %s", command, bufp);
}
/* if the output shows "OK" return success */
if (strstr(buf, "OK\r") != NULL) {
return 0;
}
return -1;
}
/**
* Function raised by signal catching
*/
void signal_callback_handler(int signum) {
return;
}
/**
* Gets the major number of the driver device
* Returns the major number on success
* -1 on failure
*/
int get_major(char *driver) {
FILE *fp;
char *line = NULL;
size_t len = 0;
ssize_t read;
char device[20];
int major = -1;
/* open /proc/devices file */
if ((fp = fopen("/proc/devices", "r")) == NULL)
err(EXIT_FAILURE, "Cannot open /proc/devices");
/* read the file line by line */
while ((major == -1) && (read = getline(&line, &len, fp)) != -1) {
/* if the driver name string is found in the line, try to get the major */
if (strstr(line, driver) != NULL) {
if (sscanf(line,"%d %s\n", &major, device) != 2)
major = -1;
}
/* free the line before getting a new one */
if (line) {
free(line);
line = NULL;
}
}
/* close /proc/devices file */
fclose(fp);
return major;
}
/**
* Creates nodes for the virtual TTYs
* Returns the number of nodes created
*/
int make_nodes(int major, char *basename, int number_nodes) {
int minor, created = 0;
dev_t device;
char node_name[15];
mode_t oldmask;
/* set a new mask to get 666 mode and stores the old one */
oldmask = umask(0);
for (minor=1; minor<number_nodes+1; minor++) {
/* append the minor number to the base name */
sprintf(node_name, "%s%d", basename, minor);
/* store a device info with major and minor */
device = makedev(major, minor);
/* create the actual character node */
if (mknod(node_name, S_IFCHR | 0666, device) != 0) {
warn("Cannot create %s", node_name);
} else {
created++;
dbg("Created %s", node_name);
}
}
/* revert the mask to the old one */
umask(oldmask);
return created;
}
/**
* Removes previously created TTY nodes
* Returns nothing, it doesn't really matter if it fails
*/
void remove_nodes(char *basename, int number_nodes) {
int node;
char node_name[15];
for (node=1; node<number_nodes+1; node++) {
/* append the minor number to the base name */
sprintf(node_name, "%s%d", basename, node);
/* unlink the actual character node */
dbg("Removing %s", node_name);
if (unlink(node_name) == -1)
warn("Cannot remove %s", node_name);
}
return;
}
int main(void) {
int serial_fd, major;
struct termios tio;
int ldisc = N_GSM0710;
struct gsm_config gsm;
char atcommand[40];
/* print global parameters */
dbg("SERIAL_PORT = %s", SERIAL_PORT);
/* open the serial port */
serial_fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
if (serial_fd == -1)
err(EXIT_FAILURE, "Cannot open %s", SERIAL_PORT);
/* get the current attributes of the serial port */
if (tcgetattr(serial_fd, &tio) == -1)
err(EXIT_FAILURE, "Cannot get line attributes");
/* set the new attrbiutes */
tio.c_iflag = 0;
tio.c_oflag = 0;
tio.c_cflag = CS8 | CREAD | CLOCAL;
tio.c_cflag |= CRTSCTS;
tio.c_lflag = 0;
tio.c_cc[VMIN] = 1;
tio.c_cc[VTIME] = 0;
/* write the speed of the serial line */
if (cfsetospeed(&tio, LINE_SPEED) < 0 || cfsetispeed(&tio, LINE_SPEED) < 0)
err(EXIT_FAILURE, "Cannot set line speed");
/* write the attributes */
if (tcsetattr(serial_fd, TCSANOW, &tio) == -1)
err(EXIT_FAILURE, "Cannot set line attributes");
/**
* Send AT commands to put the modem in CMUX mode.
* This is vendor specific and should be changed
* to fit your modem needs.
* The following matches Quectel M95.
*/
if (send_at_command(serial_fd, "AT+IFC=2,2\r") == -1)
errx(EXIT_FAILURE, "AT+IFC=2,2: bad response");
if (send_at_command(serial_fd, "AT+GMM\r") == -1)
warnx("AT+GMM: bad response");
if (send_at_command(serial_fd, "AT\r") == -1)
warnx("AT: bad response");
if (send_at_command(serial_fd, "AT+IPR=115200&w\r") == -1)
errx(EXIT_FAILURE, "AT+IPR=115200&w: bad response");
sprintf(atcommand, "AT+CMUX=0,0,5,%d,10,3,30,10,2\r", MTU);
if (send_at_command(serial_fd, atcommand) == -1)
errx(EXIT_FAILURE, "Cannot enable modem CMUX");
/* use n_gsm line discipline */
sleep(2);
if (ioctl(serial_fd, TIOCSETD, &ldisc) < 0)
err(EXIT_FAILURE, "Cannot set line dicipline. Is 'n_gsm' module registred?");
/* get n_gsm configuration */
if (ioctl(serial_fd, GSMIOC_GETCONF, &gsm) < 0)
err(EXIT_FAILURE, "Cannot get GSM multiplex parameters");
/* set and write new attributes */
gsm.initiator = 1;
gsm.encapsulation = 0;
gsm.mru = MTU;
gsm.mtu = MTU;
gsm.t1 = 10;
gsm.n2 = 3;
gsm.t2 = 30;
gsm.t3 = 10;
if (ioctl(serial_fd, GSMIOC_SETCONF, &gsm) < 0)
err(EXIT_FAILURE, "Cannot set GSM multiplex parameters");
dbg("Line dicipline set");
/* create the virtual TTYs */
if (CREATE_NODES) {
int created;
if ((major = get_major(DRIVER_NAME)) < 0)
errx(EXIT_FAILURE, "Cannot get major number");
if ((created = make_nodes(major, BASENAME_NODES, NUM_NODES)) < NUM_NODES)
warnx("Cannot create all nodes, only %d/%d have been created.", created, NUM_NODES);
}
/* detach from the terminal if needed */
if (DAEMONIZE) {
dbg("Going to background");
if (daemon(0,0) != 0)
err(EXIT_FAILURE, "Cannot daemonize");
}
/* wait to keep the line discipline enabled, wake it up with a signal */
signal(SIGINT, signal_callback_handler);
signal(SIGTERM, signal_callback_handler);
pause();
/* remove the created virtual TTYs */
if (CREATE_NODES) {
remove_nodes(BASENAME_NODES, NUM_NODES);
}
/* close the serial line */
close(serial_fd);
return EXIT_SUCCESS;
}

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Code C - [expand]
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#ifndef _LINUX_GSMMUX_H
#define _LINUX_GSMMUX_H
struct gsm_config
{
unsigned int adaption;
unsigned int encapsulation;
unsigned int initiator;
unsigned int t1;
unsigned int t2;
unsigned int t3;
unsigned int n2;
unsigned int mru;
unsigned int mtu;
unsigned int k;
unsigned int i;
unsigned int unused[8]; /* Padding for expansion without
breaking stuff */
};
#define GSMIOC_GETCONF  _IOR('G', 0, struct gsm_config)
#define GSMIOC_SETCONF  _IOW('G', 1, struct gsm_config)
struct gsm_netconfig {
unsigned int adaption; /* Adaption to use in network mode */
unsigned short protocol;/* Protocol to use - only ETH_P_IP supported */
unsigned short unused2;
char if_name[IFNAMSIZ]; /* interface name format string */
__u8 unused[28]; /* For future use */
};
#define GSMIOC_ENABLE_NET _IOW('G', 2, struct gsm_netconfig)
#define GSMIOC_DISABLE_NET _IO('G', 3)
#endif

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Original GitHub Repository

Sometimes I need to reinitialize the modem, however it seems to be blocked.

How can I reset it, preferably using AT commands to a non cmux configuration.

thanks for your time
robert