Re: Error while trying to use RS232 port on DE2 2c35 running uClinux

Altera_Forum · ‎06-20-2010

Hi all,

I try to use RS232 port on my DE2 board to communicate with my device (magnetic card reader).

But when I try to use the command "cat test.txt > /dev/ttyS0", the console appears with "/dev/ttyS0: cannot create." I am wondering if I have to check "Altera UART support" in "Device Drivers ---> Character devices ---> Serial drivers --->" or just use ttyS0 as a normal file? And how I can know that there are data coming from my device or PC? Is there buffer for data from RS232 port? :confused:

Thanks for reading! :)

Altera_Forum · ‎06-21-2010

Hi Tien,

You have to be carefull with this command "cat test.txt > /dev/ttyS0", use microcom instead. You will find it in the application selection of the make menuconfig. command will be :

microcom -s 9600 /dev/ttyS0

with 9600 the baud rate of your serial connexion.

Altera_Forum · ‎06-22-2010

thanks for replying Mr actris, I have solved that problem by updating to nios2-linux 2009 version. I can open and write data to "dev/ttyS0" well.

But I encounter another problem now. I can't read from "dev/ttyS0" by using read or fread functions. :(

here's my code:


# include <string.h>
# include <unistd.h>  
# include <fcntl.h>   
# include <errno.h>   
# include <termios.h> 
int main(void)
{
	char buf;	
	int fd1, fd2, count;
	
 	fd1 = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
	fd2 = open("/mnt/SD/t.txt",O_WRONLY);
      	if (fd1 == -1)
      	{
       		perror("open_port: Unable to open /dev/ttyS0 - ");
	}
      	
	while(count = read(fd1, buf, 10) > 0)
		write(fd2, buf, 10);
	
	close(fd1);
	close(fd2);
      //return (fd);
}