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Serial port communication in C

nimadorostkar profile image nima ・2 min read

github link for this project:
https://github.com/atrotech/comtest
How to build

git clone https://github.com/atrotech/comtest.git

cd comtest

gcc -o comtest comtest.c

Usage
./comtest -d /dev/ttyAMA3 -s 38400
Parameters

./comtest --help

comtest - interactive program of comm port
press [ESC] 3 times to quit
Usage: comtest [-d device] [-t tty] [-s speed] [-7] [-c] [-x] [-o] [-h]
-7 7 bit
-x hex mode
-o output to stdout too
-c stdout output use color
-h print this help
comtest.c :

include

include

include

include

include

include

include

include

include

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);
return -1;
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}
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) {
printf("%s",strerror(errno));

}
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}
int main(int argc, char **argv)
{
int CommFd, TtyFd;
struct termios TtyAttr;
struct termios BackupTtyAttr;
int DeviceSpeed = B38400;
int TtySpeed = B38400;
int ByteBits = CS8;
const char *DeviceName = "/dev/ttyAMA3";
const char *TtyName = "/dev/tty";
int OutputHex = 0;
int OutputToStdout = 0;
int UseColor = 0;

CommFd = open(DeviceName, O_RDWR, 0);

if (fcntl(CommFd, F_SETFL, O_NONBLOCK) < 0)
  printf("Unable set to NONBLOCK mode");
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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)
printf("Unable to set comm port");
TtyFd = open(TtyName, O_RDWR | O_NDELAY, 0);
TtyAttr.c_cflag = TtySpeed | HUPCL | ByteBits | CREAD | CLOCAL;
if (tcgetattr(TtyFd, &BackupTtyAttr) < 0)
printf("Unable to get tty");
if (tcsetattr(TtyFd, TCSANOW, &TtyAttr) < 0)
printf("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) {
printf("%s",strerror(errno));
}

undef max

if (FD_ISSET(CommFd, &ReadSetFD)) {
while (read(CommFd, &Char, 1) == 1) {
WaitFdWriteable(TtyFd);
if (write(TtyFd, &Char, 1) < 0) {
printf("%s",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) {
printf("%s",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)
printf("Unable to set tty");
return 0;
}
Makefile
CROSS=arm-linux-
all: armcomtest x86comtest
armcomtest: comtest.c
$(CROSS)gcc -Wall -O3 -o armcomtest comtest.c
x86comtest: comtest.c
gcc -o x86comtest comtest.c
clean:
@rm -vf armcomtest x86comtest *.o *~

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muhyilmaz profile image
MUHAMMED YILMAZ

bad writing