如何在C程序中通过串行终端读取二进制数据? [英] How to read a binary data over serial terminal in C program?
问题描述
我阅读了后面的链接和其他来源，但没有找到问题的答案.
I read followed links and other sources, but didn't find answer for my question.
我通过串行端口与嵌入式设备通信.默认情况下，嵌入式Linux使用此端口作为终端.但是我也想通过端口传输二进制数据(服务数据包).我的/etc/inittab文件有一个"getty"调用: 控制台::重生:/sbin/getty 115200 ttyS0
I communicate with my embedded device through a serial port. By default, embedded Linux uses this port as a terminal. But I want to transfer also binary data (service packets) through the port. My /etc/inittab file has a "getty" call: console::respawn:/sbin/getty 115200 ttyS0
我也有带字符串的/etc/passwd文件，其中"admin"用户登录后启动我的"cli"应用程序: admin:8Mt/Jtxcyg8AY:1000:0:admin:/tmp:/tmp/cli
I also have /etc/passwd file with string where "admin" user launch my "cli" application after log in: admin:8Mt/Jtxcyg8AY:1000:0:admin:/tmp:/tmp/cli
在运行程序之前，我的默认ttyS0设置是:
My default ttyS0 settings before running the program is:
~ # stty -a
speed 115200 baud;stty: standard input
line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ^J;
eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 hupcl -cstopb cread -clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon ixoff
-iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon -iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
-echoctl echoke
~ #
因此，在我的cli程序中，我执行以下操作:
So, in my cli program I do the following:
main ()
{
...
system("stty erase ^H);
system("stty -F /dev/ttyS0 -icrnl -ixon -ixoff -opost -isig -icanon -echo"); // enter in non-canonical (raw) mode
// What function do I need to use here to retrieve binary data (also symbols that > 0x7F) from /dev/ttyS0?
system("stty -F /dev/ttyS0 icrnl ixon ixoff opost isig icanon echo"); // go back to canonical mode
...
exit(0);
}
我尝试使用read()函数(使用无符号char缓冲区)来获取二进制数据，但是未能接收到正确的数据.我还预先初步打开了/dev/ttyS0以获取file_descriptor&使用read()函数.
I have attempted read() function (with unsigned char buffer) to get binary data, but failed to receive correct data. I also preliminarily open /dev/ttyS0 again to get file_descriptor & use read() func.
我的程序发送3个字节:0xAA，0x02、0xFE. 但是在syslog中，我总是看到设备收到不正确的符号:0x98、0xE6、0x18.
My program sends 3 bytes: 0xAA, 0x02, 0xFE. But in syslog I always see that device receives incorrect symbols: 0x98, 0xE6, 0x18.
怎么了?如何获取正确的二进制数据?
What is the matter? How to get correct binary data?
我目前正在测试的完整代码.
A whole code that I am testing at the moment.
#include "cli.h"
#include "glb_vars.h"
/******************************************
*** Definitions
******************************************/
#define APPLICATION_NAME "cli"
#define SERIALPORT_IS_CONSOLE
/******************************************
*** Constants
******************************************/
const char dev_name[] = DEV_NAME;
const char lineminstr[] = "\t--------------------------------------------------------\n";
/******************************************
*** Internal Function Declarations
******************************************/
CLI_RETVAL cliInit(void);
CLI_RETVAL cliClose(void);
void cliWorkLoop(Term_callback_t **term);
/******************************************
*** External Function Declarations
******************************************/
extern void Vectors_init(Term_callback_t **vec);
extern char** Menu_completion(const char * text, int start, int end);
/****************************************************************************/
int file_descr, max_fd;
struct termios tty, orig_tty;
fd_set work_set;
/****************************************************************************/
/*!
* \brief Init cli
*
* \return success or failure
* \retval CLI_SUCCESS, CLI_FAILURE
*
* \ingroup CLI
*/
/****************************************************************************/
CLI_RETVAL cliInit(void)
{
long spd;
signal(SIGINT, SIG_IGN);
signal(SIGHUP, SIG_IGN);
signal(SIGTERM, SIG_IGN);
signal(SIGABRT, SIG_IGN);
signal(SIGQUIT, SIG_IGN);
signal(SIGILL, SIG_IGN);
// system("stty -F /dev/ttyS0 -icrnl -ixon -ixoff -opost -isig -icanon -echo"); // enter in non-canonical mode
// system("stty -a");
// sleep(1);
#ifdef SERIALPORT_IS_CONSOLE
file_descr = STDIN_FILENO;
SYS_LOG_DEBUG("SERIALPORT IS CONSOLE");
#else
SYS_LOG_DEBUG("SERIALPORT IS NOT CONSOLE");
file_descr = open("/dev/ttyS0", O_RDWR | O_ASYNC | O_NDELAY);
if (file_descr == -1) {
// Could not open the port
perror("unable to open /dev/ttyS0");
exit(1);
}
#endif
if(tcgetattr(file_descr, &tty) < 0)
{
perror("unable to get tty attributes");
exit(1);
}
// backup tty, make it raw and apply changes
orig_tty = tty;
spd = B115200;
cfsetospeed(&tty, (speed_t)spd);
cfsetispeed(&tty, (speed_t)spd);
cfmakeraw(&tty);
tty.c_cc[VMIN] = 1;
tty.c_cc[VTIME] = 10;
tty.c_cflag &= ~CSTOPB;
tty.c_cflag &= ~CRTSCTS; /* no HW flow control? */
tty.c_cflag |= CLOCAL | CREAD;
tcsetattr(file_descr, TCSANOW, &tty);
// // update local mode flags
// tty.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
//// // renew control mode flags
//// tty.c_cflag &= ~(CBAUD | CSIZE | CSTOPB | PARENB | PARODD);
//// tty.c_cflag |= (BAUD | DATABITS | STOPBITS | PARITYON | PARITY);
// // select 'raw' output mode
// tty.c_oflag &= ~OPOST;
// // disable mapping for input mode
// tty.c_iflag &= ~(INLCR | ICRNL);
//
//
// if(tcsetattr(file_descr, TCSAFLUSH, &tty) < 0)
// {
// perror("unable to set tty attributes");
// exit(1);
// }
//
// Setup fd_set
FD_ZERO(&work_set);
FD_SET(file_descr, &work_set);
max_fd = file_descr + 1;
/* Readline lib init */
// Define application name for readline library
rl_readline_name = APPLICATION_NAME;
// Update Pointer to alternative function to create matches.
rl_attempted_completion_function = Menu_completion;
// Start readline with reading /etc/inputrc file
using_history();
stifle_history(CLI_MAX_HISTORY_SIZE);
// Some other initialization code
// ...
// ...
return CLI_SUCCESS;
}
/****************************************************************************/
/*!
* \brief Close cli
*
* \return success or failure
* \retval CLI_SUCCESS, CLI_FAILURE
*
* \ingroup CLI
*/
/****************************************************************************/
CLI_RETVAL cliClose(void)
{
// system("stty -F /dev/ttyS0 icrnl ixon ixoff opost isig icanon echo"); // enter in canonical mode
tcsetattr(file_descr, TCSANOW, &orig_tty);
// if(tcsetattr(file_descr, TCSAFLUSH, &orig_tty) < 0)
// {
// perror("unable to set orig_tty attributes");
// exit(1);
// }
close(file_descr);
return CLI_SUCCESS;
}
/****************************************************************************/
/*!
* \brief Main cli processing loop
*
* \no return
*
* \ingroup CLI
*/
/****************************************************************************/
void cliWorkLoop(Term_callback_t **term)
{
Term_callback_t *cur_term;
int8 *commandString;
uint8 ret = CLI_REFRESH, no_prompt;
char prompt_str[20];
while (1) {
cur_term = *term;
global_cmd_compl_pointer = cur_term->cmd_list;
commandString = NULL;
sprintf(prompt_str, "%s:~> ", dev_name);
if(ret == CLI_REFRESH) {
CLEAR_SCR();
if(cur_term->out != NULL) {
cur_term->out(term, commandString, &ret);
no_prompt = ret;
}
CURSOR_DOWN();
}
int n;
struct timeval timeout;
uint8 tmpBuf[32];
while (1)
{
// Setup Timeout
timeout.tv_sec = 60;
timeout.tv_usec = 0;
// Wait for new connections
n = select(max_fd, &work_set, NULL, NULL, &timeout);
if (n < 0)
{
perror("select #2 failed");
break;
}
if (n > 0)
{
/* У нас есть ввод */
if (FD_ISSET(file_descr, &work_set))
{
if (read(file_descr, tmpBuf, 10) < 0) {
perror("cannot read");
exit(1);
}
else
{
SYS_LOG_DEBUG("READ first 4 chars: 0x%X,0x%X,0x%X,0x%X", tmpBuf[0], tmpBuf[1], tmpBuf[2], tmpBuf[3]);
}
}
break;
}
}
//
//
// n = read(file_descr, tmpBuf, 5);
// if (n > 0) {
// unsigned char *p = tmpBuf;
//
// while (n-- > 0)
// printf(" 0x%x", *p++);
// printf("\r\n");
// } else {
// printf("failed to read: %d\r\n", n);
// }
//
//
exit(0);
}
CLEAR_SCR();
return;
}
/****************************************************************************/
/*!
* \brief Main cli function
*
* \param[in] argc - argument number.
* \param[in,out] argv - argument values entered by user.
*
* \return success or failure
* \retval EXIT_SUCCESS, EXIT_FAILURE
*
*
* \ingroup CLI
*/
/****************************************************************************/
int main(int argc, char *argv[])
{
Term_callback_t *term;
char logname[16];
FILE *fp;
/* Set mask for file operation */
umask(0);
system("stty erase ^H");
openlog("cli", LOG_CONS, LOG_USER);
/* Write cli start log */
syslog(LOG_NOTICE, "Console startup. Software version: %s", VERSION);
/* Find login name */
strcpy(logname, "noname");
if ((fp = popen( "whoami", "r" )) == NULL)
{
SYS_LOG_ERR("Can't open process for \"whoami\" command.");
} else
{
fgets(logname, 16, fp);
pclose(fp);
}
SYS_LOG_INFO("Console is entered by \"%s\".", logname); //getenv("USER")
/* Console initialization */
if (cliInit() != CLI_SUCCESS) {
SYS_LOG_CRIT("CLI init failed");
return EXIT_FAILURE;
}
Vectors_init(&term);
/* Console work loop */
cliWorkLoop(&term);
cliClose();
/* Exiting from cli */
SYS_LOG_INFO("\"%s\" exited from console.", logname);
return EXIT_SUCCESS;
}
推荐答案
system("stty erase ^H);
system("stty -F /dev/ttyS0 -icrnl -ixon -ixoff -opost -isig -icanon -echo"); // enter into non-canonical (raw) mode
这将不足以使串行端口进入原始或非规范模式的代码(以及根据POSIX约定的不良编码实践).
在C和Linux中，最简单的方法是使用cfmakeraw()函数，该函数在GNU libc和uClibc库中都可用.使用手册页获取由cfmakeraw()修改的 termios 结构成员的详细信息.
请注意，cfmakeraw()将以原始模式将串行端口设置为8位的数据长度和 no 奇偶校验，以将总字符帧设置为10位(假设一个停止位).
This would be insufficient code (and poor coding practice per POSIX conventions) to put the serial port into raw or non-canonical mode.
The easiest method in C and Linux is to use the function cfmakeraw() which is available in both the GNU libc and uClibc libraries. Use the man page to obtain the details on the termios structure members that are modified by cfmakeraw().
Beware that cfmakeraw() will setup the serial port in raw mode for a data length of 8 bits and no parity, for a total character frame of 10 bits (assuming one stop bit).
首选方法是保留 termios 结构的副本(用于在程序退出时恢复)，并且仅修改所需的标志位(而不是编写完整的结构成员).
The preferred method is preserving a copy of the termios stucture (for restoration on program exit) and only modifying the required flag bits (rather than writing the complete structure members).
适用于我的ARM SoC的代码为:
Code that works on my ARM SoC is:
#include <stdio.h>
#include <stdlib.h>
#include <sys/un.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/syslog.h>
#include <termios.h>
#define SERIALPORT_IS_CONSOLE
main()
{
struct termios tty;
struct termios savetty;
speed_t spd;
unsigned int sfd;
unsigned char buf[80];
int reqlen = 79;
int rc;
int rdlen;
int pau = 0;
#ifdef SERIALPORT_IS_CONSOLE
sfd = STDIN_FILENO;
#else
sfd = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
#endif
if (sfd < 0) {
syslog(LOG_DEBUG, "failed to open: %d, %s", sfd, strerror(errno));
exit (-1);
}
syslog(LOG_DEBUG, "opened sfd=%d for reading", sfd);
rc = tcgetattr(sfd, &tty);
if (rc < 0) {
syslog(LOG_DEBUG, "failed to get attr: %d, %s", rc, strerror(errno));
exit (-2);
}
savetty = tty; /* preserve original settings for restoration */
spd = B115200;
cfsetospeed(&tty, (speed_t)spd);
cfsetispeed(&tty, (speed_t)spd);
cfmakeraw(&tty);
tty.c_cc[VMIN] = 1;
tty.c_cc[VTIME] = 10;
tty.c_cflag &= ~CSTOPB;
tty.c_cflag &= ~CRTSCTS; /* no HW flow control? */
tty.c_cflag |= CLOCAL | CREAD;
rc = tcsetattr(sfd, TCSANOW, &tty);
if (rc < 0) {
syslog(LOG_DEBUG, "failed to set attr: %d, %s", rc, strerror(errno));
exit (-3);
}
do {
unsigned char *p = buf;
rdlen = read(sfd, buf, reqlen);
if (rdlen > 0) {
if (*p == '\r')
pau = 1;
syslog(LOG_DEBUG, "read: %d, 0x%x 0x%x 0x%x", \
rdlen, *p, *(p + 1), *(p + 2));
} else {
syslog(LOG_DEBUG, "failed to read: %d, %s", rdlen, strerror(errno));
}
} while (!pau);
tcsetattr(sfd, TCSANOW, &savetty);
close(sfd);
exit (0);
}
已编译的程序已加载&在目标板上执行.
The compiled program is loaded & executed on the target board.
从串行通讯链接的主机端发送具有以下内容的文件seq.bin:
From the host side of the serial comm link, the file seq.bin with the following contents is sent:
$ od -t x1 seq.bin
0000000 aa 02 fe
0000003
然后是"ABC"在主机(正在运行minicom终端仿真器程序)上键入，然后回车.
该程序在目标上终止，然后检查系统日志:
Then "ABC" is typed on the host (which is running the minicom terminal emulator program), followed by a carriage return.
The program terminates on the target, and the syslog is then examined:
# tail /var/log/messages
Sep xx xx:xx:42 atmel_soc user.info kernel: EXT3 FS on nvsram, internal journal
Sep xx xx:xx:42 atmel_soc user.info kernel: EXT3-fs: mounted filesystem with or.
Sep xx xx:xx:42 atmel_soc user.info kernel: kjournald starting. Commit intervas
Sep xx xx:xx:18 atmel_soc auth.info login[431]: root login on 'ttyS0'
Sep xx xx:xx:04 atmel_soc user.debug syslog: opened sfd=0 for reading
Sep xx xx:xx:14 atmel_soc user.debug syslog: read: 3, 0xaa 0x2 0xfe
Sep xx xx:xx:50 atmel_soc user.debug syslog: read: 1, 0x41 0x2 0xfe
Sep xx xx:xx:51 atmel_soc user.debug syslog: read: 1, 0x42 0x2 0xfe
Sep xx xx:xx:51 atmel_soc user.debug syslog: read: 1, 0x43 0x2 0xfe
Sep xx xx:xx:52 atmel_soc user.debug syslog: read: 1, 0xd 0x2 0xfe
#
二进制数据已完整接收.
The binary data has been received intact.
请注意，由于这是原始模式，并且输入的字符相对较慢地输入，因此read()返回"partial"(部分).数据和用户程序将负责将数据缓冲/组合为完整的消息".如果消息的长度固定，则可以将c_cc[VMIN]成员 设置为消息长度.但是当帧同步丢失时，请注意消息成帧问题和复杂性！
Note that since this is raw mode and the typed chars were entered relatively slowly, the read() returns "partial" data and the user program would be responsible for buffering/assembling the data into complete "messages". If the messages are of fixed length, then c_cc[VMIN]member could be set to the message length. But beware of message framing issues and complications when frame sync is lost!
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