Hello, doubt with serial port............

webquinty · 10-23-2008, 02:34 AM

Hello,

I hava some threads, and one of them is to receive commands from other PC with serial port.

The configuration of serial port is:

Quote:

tcgetattr(fd, &options_new);

cfsetispeed(&options_new, B38400);
cfsetospeed(&options_new, B38400);

options_new.c_cflag |= (CLOCAL | CREAD);

options_new.c_cflag &= ~PARENB;
options_new.c_cflag &= ~CSTOPB;
options_new.c_cflag &= ~CSIZE;
options_new.c_cflag |= CS8;

options_new.c_cflag &= ~(IXON | IXOFF | IXANY);

options_new.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);

options_new.c_cc[VMIN] = 0;
options_new.c_cc[VTIME] = 0;

tcsetattr(fd, TCSANOW, &options_new);

I supposed that raw input allow me to receive all values without any problem, but when I send this comand for example:

Quote:

0x01 0x04 0x11 0x45 0x1f 0x67 crc

The problem is that 3 byte is backspace I my program receive this:

Quote:

0x01 0x04 0x45 0x1f 0x67 crc

In few words, byte 0x11 (backspace) delete one byte.
How can I configure serial port to receive all charcaters without theese problems.

Best regards.

grumpf · 10-24-2008, 10:58 AM

the best way is to check with minicom what is going on.
if somethings is eating BS you have a filter enabled use cfmakeraw() is our prg
and stty -a </dev/ttyS0 to check.
are you sure that nothing else is access the port ? it can have some complicated consequences.
(see: mgetty and friends)

jf.argentino · 10-24-2008, 11:46 AM

If I well remember, the serial port is mainly used for as a terminal IO, it means that some character (or characters sequence) have special purpose... You can disabled these "special" characters interpretation, but I don't remember how... Maybe add the flag O_NOCTTY when opening the device, or take a look to the field "c_cc" (control characters) of the termios structure.
Hope this help...

estabroo · 10-24-2008, 12:11 PM

easiest way is to use cfmakeraw(&new_options) and then set any additional parameters you want.

webquinty · 10-27-2008, 08:22 AM

Quote:

Originally Posted by estabroo

easiest way is to use cfmakeraw(&new_options) and then set any additional parameters you want.

Thank you very much,

I have found my problem:

Quote:

//********************************************************
// chosee raw output
//********************************************************
options_new.c_oflag &= ~OPOST;

I did not change this, then some character have special purpose. But with this option, I can send data in raw mode.

Sorry for it, perhaps I coudl fix it if I look for more information in the net.

Best regards