适用于所有arm开发板的串口编程示例(Linux)
本程序摘自友善之臂最新Linux示例(光盘中的/linux/exapmples.tgz解压出来可得此文件)
说明:
comtest
程序是友善之臂早期开发的一个串口测试程序,它其实是一个十分简易的串口终端程序,类似于
linux
中的
minicom
,该程序与硬件无关,因此相同的代码不仅适用于任何
Arm-linux
开发板平台,也可以在
PC linux
上运行使用,方法都是完全一样的。通过该程序你可以了解串口编程的一些常见关键设置,对于
linux
下串口编程很有帮助和借鉴意义,该程序虽然十分短小,但设计极为严谨巧妙,我们对此就不详细解释了,下面是它的完整源代码:
注:本程序版权归属友善之臂所有,任何单位或个人转载或复制均需注明出处,且不得用于商业用途。
# include
# include
# include
# include
# include
# include
# include
# include
# include
static void Error(const char *Msg)
{
fprintf (stderr, "%s/n", Msg);
fprintf (stderr, "strerror() is %s/n", strerror(errno));
exit(1);
}
static void Warning(const char *Msg)
{
fprintf (stderr, "Warning: %s/n", Msg);
}
static int SerialSpeed(const char *SpeedString)
{
int SpeedNumber = atoi(SpeedString);
# define TestSpeed(Speed) if (SpeedNumber == Speed) return B##Speed
TestSpeed(1200);
TestSpeed(2400);
TestSpeed(4800);
TestSpeed(9600);
TestSpeed(19200);
TestSpeed(38400);
TestSpeed(57600);
TestSpeed(115200);
TestSpeed(230400);
Error("Bad speed");
return -1;
}
static void PrintUsage(void)
{
fprintf(stderr, "comtest - interactive program of comm port/n");
fprintf(stderr, "press [ESC] 3 times to quit/n/n");
fprintf(stderr, "Usage: comtest [-d device] [-t tty] [-s speed] [-7] [-c] [-x] [-o] [-h]/n");
fprintf(stderr, " -7 7 bit/n");
fprintf(stderr, " -x hex mode/n");
fprintf(stderr, " -o output to stdout too/n");
fprintf(stderr, " -c stdout output use color/n");
fprintf(stderr, " -h print this help/n");
exit(-1);
}
static inline void WaitFdWriteable(int Fd)
{
fd_set WriteSetFD;
FD_ZERO(&WriteSetFD);
FD_SET(Fd, &WriteSetFD);
if (select(Fd + 1, NULL, &WriteSetFD, NULL, NULL) < 0) {
Error(strerror(errno));
}
}
int main(int argc, char **argv)
{
int CommFd, TtyFd;
struct termios TtyAttr;
struct termios BackupTtyAttr;
int DeviceSpeed = B115200;
int TtySpeed = B115200;
int ByteBits = CS8;
const char *DeviceName = "/dev/ttyS0";
const char *TtyName = "/dev/tty";
int OutputHex = 0;
int OutputToStdout = 0;
int UseColor = 0;
opterr = 0;
for (;;) {
int c = getopt(argc, argv, "d:s:t:7xoch");
if (c == -1)
break;
switch(c) {
case 'd':
DeviceName = optarg;
break;
case 't':
TtyName = optarg;
break;
case 's':
if (optarg[0] == 'd') {
DeviceSpeed = SerialSpeed(optarg + 1);
} else if (optarg[0] == 't') {
TtySpeed = SerialSpeed(optarg + 1);
} else
TtySpeed = DeviceSpeed = SerialSpeed(optarg);
break;
case 'o':
OutputToStdout = 1;
break;
case '7':
ByteBits = CS7;
break;
case 'x':
OutputHex = 1;
break;
case 'c':
UseColor = 1;
break;
case '?':
case 'h':
default:
PrintUsage();
}
}
if (optind != argc)
PrintUsage();
CommFd = open(DeviceName, O_RDWR, 0);
if (CommFd < 0)
Error("Unable to open device");
if (fcntl(CommFd, F_SETFL, O_NONBLOCK) < 0)
Error("Unable set to NONBLOCK mode");
memset(&TtyAttr, 0, sizeof(struct termios));
TtyAttr.c_iflag = IGNPAR;
TtyAttr.c_cflag = DeviceSpeed | HUPCL | ByteBits | CREAD | CLOCAL;
TtyAttr.c_cc[VMIN] = 1;
if (tcsetattr(CommFd, TCSANOW, &TtyAttr) < 0)
Warning("Unable to set comm port");
TtyFd = open(TtyName, O_RDWR | O_NDELAY, 0);
if (TtyFd < 0)
Error("Unable to open tty");
TtyAttr.c_cflag = TtySpeed | HUPCL | ByteBits | CREAD | CLOCAL;
if (tcgetattr(TtyFd, &BackupTtyAttr) < 0)
Error("Unable to get tty");
if (tcsetattr(TtyFd, TCSANOW, &TtyAttr) < 0)
Error("Unable to set tty");
for (;;) {
unsigned char Char = 0;
fd_set ReadSetFD;
void OutputStdChar(FILE *File) {
char Buffer[10];
int Len = sprintf(Buffer, OutputHex ? "%.2X " : "%c", Char);
fwrite(Buffer, 1, Len, File);
}
FD_ZERO(&ReadSetFD);
FD_SET(CommFd, &ReadSetFD);
FD_SET( TtyFd, &ReadSetFD);
# define max(x,y) ( ((x) >= (y)) ? (x) : (y) )
if (select(max(CommFd, TtyFd) + 1, &ReadSetFD, NULL, NULL, NULL) < 0) {
Error(strerror(errno));
}
# undef max
if (FD_ISSET(CommFd, &ReadSetFD)) {
while (read(CommFd, &Char, 1) == 1) {
WaitFdWriteable(TtyFd);
if (write(TtyFd, &Char, 1) < 0) {
Error(strerror(errno));
}
if (OutputToStdout) {
if (UseColor)
fwrite("/x1b[01;34m", 1, 8, stdout);
OutputStdChar(stdout);
if (UseColor)
fwrite("/x1b[00m", 1, 8, stdout);
fflush(stdout);
}
}
}
if (FD_ISSET(TtyFd, &ReadSetFD)) {
while (read(TtyFd, &Char, 1) == 1) {
static int EscKeyCount = 0;
WaitFdWriteable(CommFd);
if (write(CommFd, &Char, 1) < 0) {
Error(strerror(errno));
}
if (OutputToStdout) {
if (UseColor)
fwrite("/x1b[01;31m", 1, 8, stderr);
OutputStdChar(stderr);
if (UseColor)
fwrite("/x1b[00m", 1, 8, stderr);
fflush(stderr);
}
if (Char == '/x1b') {
EscKeyCount ++;
if (EscKeyCount >= 3)
goto ExitLabel;
} else
EscKeyCount = 0;
}
}
}
ExitLabel:
if (tcsetattr(TtyFd, TCSANOW, &BackupTtyAttr) < 0)
Error("Unable to set tty");
return 0;
}
编译脚本:
在arm平台上:
本脚本适用于最新编译器arm-linux-gcc-4.3.2 with EABI
#!/bin/bash
arm-linux-gcc -Wall -O3 -o armcomtest com_test.c
arm-linux-strip --strip-all armcomtest
编译可得到armcomtest执行程序(所有友善的开发板均已经包含此执行程序)
使用其他编译器,可以这样:
arm-linux-gcc -o armcomtest com_test.c
在x86平台:
gcc -o comtest com_test.c
可以编译出comtest程序,它相当于一个微型的minicom
该程序运行后的退出方式:连续按三次"ESC"按键(就是你的PC键盘)