串口定义参数详解

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打开串口

在 Linux 下串口文件是位于 /dev 下的。串口一为 /dev/ttyS0，串口二为 /dev/ttyS1。打开串口是通过使用标准的文件打开函数操作：

int fd;
/*以读写方式打开串口*/
fd = open( "/dev/ttyS0", O_RDWR);
if (-1 == fd){
/* 不能打开串口一*/
perror(" 提示错误！");
}

设置串口

　　最基本的设置串口包括波特率设置，效验位和停止位设置。串口的设置主要是设置 struct termios 结构体的各成员值。

struct termio
{ unsigned short c_iflag; /* 输入模式标志 */
unsigned short c_oflag; /* 输出模式标志 */
unsigned short c_cflag; /* 控制模式标志*/
unsigned short c_lflag; /* local mode flags */
unsigned char c_line; /* line discipline */
unsigned char c_cc[NCC]; /* control characters */
};

下面就是termios.h的定义：
SYNOPSIS


#include <termios.h>

DESCRIPTION

The <termios.h> header contains the definitions used by the terminal I/O interfaces (see the XBD specification, General Terminal Interface for the structures and names defined).
The termios Structure
The following data types are defined through typedef:
cc_t
Used for terminal special characters.
speed_t
Used for terminal baud rates.
tcflag_t
Used for terminal modes.
The above types are all unsigned integral types.
The termios structure is defined, and includes at least the following members:
tcflag_t  c_iflag     input modes
tcflag_t  c_oflag     output modes
tcflag_t  c_cflag     control modes
tcflag_t  c_lflag     local modes
cc_t      c_cc[NCCS]  control chars
 
A definition is given for:
NCCS
Size of the array c_cc for control characters.
The following subscript names for the array c_cc are defined:
Subscript Usage Canonical Mode Non-canonical Mode Description VEOF EOF character VEOL EOL character VERASE ERASE character VINTR VINTR INTR character VKILL KILL character VMIN MIN value VQUIT VQUIT QUIT character VSTART VSTART START character VSTOP VSTOP STOP character VSUSP VSUSP SUSP character VTIME TIME value The subscript values are unique, except that the VMIN and VTIME subscripts may have the same values as the VEOF and VEOL subscripts, respectively.
Input Modes
The c_iflag field describes the basic terminal input control:
BRKINT
Signal interrupt on break.
ICRNL
Map CR to NL on input.
IGNBRK
Ignore break condition.
IGNCR
Ignore CR
IGNPAR
Ignore characters with parity errors.
INLCR
Map NL to CR on input.
INPCK
Enable input parity check.
ISTRIP
Strip character
IUCLC
Map upper-case to lower-case on input (LEGACY).
IXANY
Enable any character to restart output.
IXOFF
Enable start/stop input control.
IXON
Enable start/stop output control.
PARMRK
Mark parity errors.
Output Modes
The c_oflag field specifies the system treatment of output:
OPOST
Post-process output
OLCUC
Map lower-case to upper-case on output (LEGACY).
ONLCR
Map NL to CR-NL on output.
OCRNL
Map CR to NL on output.
ONOCR
No CR output at column 0.
ONLRET
NL performs CR function.
OFILL
Use fill characters for delay.
NLDLY
Select newline delays:
NL0
Newline character type 0.
NL1
Newline character type 1.

CRDLY
Select carriage-return delays:
CR0
Carriage-return delay type 0.
CR1
Carriage-return delay type 1.
CR2
Carriage-return delay type 2.
CR3
Carriage-return delay type 3.

TABDLY
Select horizontal-tab delays:
TAB0
Horizontal-tab delay type 0.
TAB1
Horizontal-tab delay type 1.
TAB2
Horizontal-tab delay type 2.
TAB3
Expand tabs to spaces.

BSDLY
Select backspace delays:
BS0
Backspace-delay type 0.
BS1
Backspace-delay type 1.

VTDLY
Select vertical-tab delays:
VT0
Vertical-tab delay type 0.
VT1
Vertical-tab delay type 1.

FFDLY
Select form-feed delays:
FF0
Form-feed delay type 0.
FF1
Form-feed delay type 1.

Baud Rate Selection
The input and output baud rates are stored in the termios structure. These are the valid values for objects of type speed_t. The following values are defined, but not all baud rates need be supported by the underlying hardware.
B0
Hang up
B50
50 baud
B75
75 baud
B110
110 baud
B134
134.5 baud
B150
150 baud
B200
200 baud
B300
300 baud
B600
600 baud
B1200
1200 baud
B1800
1800 baud
B2400
2400 baud
B4800
4800 baud
B9600
9600 baud
B19200
19200 baud
B38400
38400 baud
Control Modes
The c_cflag field describes the hardware control of the terminal; not all values specified are required to be supported by the underlying hardware:
CSIZE
Character size:
CS5
5 bits.
CS6
6 bits.
CS7
7 bits.
CS8
8 bits.

CSTOPB
Send two stop bits, else one.
CREAD
Enable receiver.
PARENB
Parity enable.
PARODD
Odd parity, else even.
HUPCL
Hang up on last close.
CLOCAL
Ignore modem status lines.
Local Modes
The c_lflag field of the argument structure is used to control various terminal functions:
ECHO
Enable echo.
ECHOE
Echo erase character as error-correcting backspace.
ECHOK
Echo KILL.
ECHONL
Echo NL.
ICANON
Canonical input (erase and kill processing).
IEXTEN
Enable extended input character processing.
ISIG
Enable signals.
NOFLSH
Disable flush after interrupt or quit.
TOSTOP
Send SIGTTOU for background output.
XCASE
Canonical upper/lower presentation (LEGACY).
Attribute Selection
The following symbolic constants for use with tcsetattr() are defined:
TCSANOW
Change attributes immediately.
TCSADRAIN
Change attributes when output has drained.
TCSAFLUSH
Change attributes when output has drained; also flush pending input.
Line Control
The following symbolic constants for use with tcflush() are defined:
TCIFLUSH
Flush pending input. Flush untransmitted output.
TCIOFLUSH
Flush both pending input and untransmitted output.
TCOFLUSH
Flush untransmitted output.
The following symbolic constants for use with tcflow() are defined:
TCIOFF
Transmit a STOP character, intended to suspend input data.
TCION
Transmit a START character, intended to restart input data.
TCOOFF
Suspend output.
TCOON
Restart output.
The following are declared as functions and may also be defined as macros. Function prototypes must be provided for use with an ISO C compiler.
                                                speed_t cfgetispeed(const struct termios *);
                                                speed_t cfgetospeed(const struct termios *);
                                                int     cfsetispeed(struct termios *, speed_t);
                                                int     cfsetospeed(struct termios *, speed_t);
                                                int     tcdrain(int);
                                                int     tcflow(int, int);
                                                int     tcflush(int, int);
                                                int     tcgetattr(int, struct termios *);
                                                pid_t   tcgetsid(int);
                                                int     tcsendbreak(int, int);
                                                int     tcsetattr(int, int, struct termios *);
                                                
                                                

APPLICATION USAGE

The following names are commonly used as extensions to the above, therefore portable applications must not use them:
CBAUD EXTB VDSUSP DEFECHO FLUSHO VLNEXT ECHOCTL LOBLK VREPRINT ECHOKE PENDIN VSTATUS ECHOPRT SWTCH VWERASE EXTA VDISCARD

FUTURE DIRECTIONS

None.