failed to read on /dev/ttyUSB0

Hi,

What are you trying to do ?

Are you testing the device "USB2513" ?

Hello

yes i try to read/write on dev/ttyUSB0, wich is an USB->serial device

thanks for your reply

regards

Hi,

Try the below code.

Ex:

To generate "read" app.

arm-arago-linux-gnueabi-gcc serial_testing.c -o read

To generate "write" app.

arm-arago-linux-gnueabi-gcc serial_testing.c -o write

To Run:

./read  /dev/ttyUSB0 "" 115200 > /root/log_usb.txt &

./write  /dev/ttyUSB0 "Testing" 115200

Note:

Short the Rx & Tx pins (2,3) of serial port

/******************************************************************************
 *
 * This code used to test the serial communication
 *
 *
 * Usage : ./serial /dev/ttyS0 "Hello World" 9600
 *
 ******************************************************************************/

/* Ver 1.0
 *
 * Created on: 21-May-2014
 * Author : Titusrathinaraj Stalin
 * E-mail & Feedbacks to : x0213399@ti.com
 *
 ******************************/

/* Include linux kernel header files */
#include <stdio.h>
#include<fcntl.h>
#include<termios.h>
#include<string.h>

int fd_serial;

//char tes[] = "Testing";

int Open(char a[10],int baudrate)
{
	// Object For Struct Termios .
	struct termios options;

	// ser1 || ttyS0=> Com Port1 File Present In /dev Directory .
	// open => Function Com Port 1 .
	fd_serial=open(a, O_RDWR|O_NOCTTY|O_NDELAY);
	// Error Handle .
	if(fd_serial==-1)
	{
		printf(" Cannot Open Port : %s \n",a);
		return -1;
	}
	fcntl(fd_serial,F_SETFL,0); 
	tcgetattr(fd_serial,&options);
	cfsetispeed(&options,baudrate);// Function To Set Baud Rate Of Input Stream .
	cfsetospeed(&options,baudrate);// Function To Set Baud Rate Of Output Stream .
	options.c_cflag |= (CLOCAL | CREAD );// Options For Reading From Devices .
	options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);//Option For Desable Canonical Input .
	options.c_oflag &= ~OPOST;//Option For Desable Canonical Output .
	options.c_cc[VMIN]=1;// Options For Time Outs .
	options.c_cc[VTIME]=10;
	tcsetattr(fd_serial,TCSANOW,&options);// Update Changes .
	//printf("\n Succeeded In  Openning Port : %s\n",a);
	return fd_serial;// Return Device Ptr .
}

Write(int fd,char *data)
{
	int i,k;
	char ch;
	for (i=0;i<strlen(data);i++)
	{
		ch = data[i];
		k = write(fd,&ch,1);
	}
	i = 13;
	k = write(fd,&i,1);
//	printf("writing %d  %c\n",k,i);
}

Read(int fd ,char *data)
{
	int i;
	char ch ;
	while(read(fd,&ch,1))
	printf(" %c",ch);
}

int main ( int argc, char *argv[] )
{

if ( argc != 4 ) /* argc should be 3 for correct execution */
	{
        /* We print argv[0] assuming it is the program name */
        printf( "Usage: %s <COM port name>  <msg> <baud rate>\n Ex: %s /dev/ttyS0 \"Testing\" 9600 \n", argv[0],argv[0] );
	}
else
	{
	Open(argv[1],argv[3]);
//	Write(fd_serial,argv[2]);	//Comment this line to generate 'read' app
	Read(fd_serial,argv[2]);	//Comment this line to generate 'write' app
	}

return 0;
}

Hi,

when i write on /dev/ttyUSB0, that's OK, i get my characters on an hyperterminal, but when i want to read, the caracters received aren't those emited by the hyperterminal. (for example a 'm' becomes'I', h becomes 'J'...)

I hope your code might have problem,

Please try the above code and update the result to us.

Hi,

Try to run like below.

Ex:

To generate "read" app.

host$ arm-arago-linux-gnueabi-gcc serial_testing.c -o read

To generate "write" app.

host$ arm-arago-linux-gnueabi-gcc serial_testing.c -o write

To Run:

Open telnet connection or ssh connection :

telnet#./read  /dev/ttyUSB0 "" 115200

In Console

target# ./write  /dev/ttyUSB0 "Testing" 115200

Hello

i tried your code

but get same problem reading /dev/ttyUSB0 :

sending K (fro hyperterminal) : we read  J=0x 74    (on custom board)                                                           
sending  : we read  0x  18                                                             
sending : we read  I =0x73

Hi,

Which string have you send to "ttyUSB0" ?

single letter or string ?

Is the string one letter got shifted?

Ex:

If you sent "Hi" then Are you receiving "i" letter alone instead "Hi" ?

Please provide your logs with commands what you executed.

Hi

thanks for your reply

there is no real rules : for example if i send a 'm' from PC i receive a 'I', a 'k'-> 'J', 'n'->'$'...

'Hi' sent will gives me 0x11, 0x4b

I can transmit well to PC

Is there something special to do with FTDI driver for embedded linux on ARM 3352 ?

Thanks

Here is my com initialization code

void COM_init(int comport)
{
    struct     termios    termios_p;
    int        fd=-1;
    //open serial COM
    switch(comport)
    {
        case 1:
            //if ( (com_fd1=open(COM_USB0,O_RDWR)) == -1 )
            if ( (com_fd1=open(COM_USB0,O_RDWR|O_NOCTTY|O_NDELAY )) == -1 )
            {
//                if ( (com_fd1=open(COM_USB4,O_RDWR )) == -1 )
                {
//                    perror("open tty232USB0\r\n");
                }
            }
            fd=com_fd1;
            break;
        case 2:
            if ( (com_fd2=open(COM_USB1,O_RDWR )) == -1 )
            {
//                if ( (com_fd2=open(COM_USB5,O_RDWR )) == -1 )
                {
//                    perror("open tty232USB1\r\n");
                }
            }
            fd=com_fd2;
            break;
        case 3:
            if ( (com_fd3=open(COM_USB2,O_RDWR )) == -1 )
            {
//                if ( (com_fd3=open(COM_USB6,O_RDWR )) == -1 )
                {
//                    perror("open tty232USB2\r\n");
                }
            }
            fd=com_fd3;
            break;
        case 4:
            if ( (com_fd4=open(COM_USB3,O_RDWR )) == -1 )
            {
//                if ( (com_fd4=open(COM_USB7,O_RDWR )) == -1 )
                {
//                    perror("open tty232USB3\r\n");
                }
            }
            fd=com_fd4;
            break;
        case 5:
            if ( (com_fd5=open(COM_USB4,O_RDWR )) == -1 )
            {
//                if ( (com_fd5=open("/dev/tty485USB4",O_RDWR )) == -1 )
                {
//                    perror("open tty485USB0\r\n");
                }
            }
            fd=com_fd5;
            break;
        case 6:
            if ( (com_fd6=open(COM_USB5,O_RDWR )) == -1 )
            {
//                if ( (com_fd6=open("/dev/tty485USB5",O_RDWR )) == -1 )
                {
//                    perror("open tty485USB1\r\n");
                }
            }
            fd=com_fd6;
            break;
        case 7:
            if ( (com_fd7=open(COM_USB6,O_RDWR )) == -1 )
            {
//                if ( (com_fd6=open("/dev/tty485USB5",O_RDWR )) == -1 )
                {
//                    perror("open tty485USB1\r\n");
                }
            }
            fd=com_fd7;
            break;
        case 8:
            if ( (com_fd8=open(COM_USB7,O_RDWR )) == -1 )
            {
//                if ( (com_fd6=open("/dev/tty485USB5",O_RDWR )) == -1 )
                {
//                    perror("open tty485USB1\r\n");
                }
            }
            fd=com_fd8;
            break;
        default:
            printf("wrong port COM %d\r\n",comport);
            break;
    }


    //read COM parameter
    if (tcgetattr(fd,&termios_p) != 0)
    {
        printf ("error %d from tcgetattr\r\n", errno);
    }

    //set baud rate
    termios_p.c_cflag = B9600  | CS8;
//    termios_p.c_cflag = B115200  | CS8;

    termios_p.c_lflag = 0;                    // no signaling chars, no echo,
    termios_p.c_oflag = 0;                    // no remapping, no delays
    termios_p.c_cc[VMIN]  = 0;                // read doesn't block
    termios_p.c_cc[VTIME] = 0;               // no timeout
    //TODO
    if ((comport==5)||(comport==6))
        termios_p.c_cc[VTIME] = 5;

    //shut off parity
    termios_p.c_cflag &= ~(PARENB | PARODD);

    //one stop bit
    termios_p.c_cflag &= ~CSTOPB;

    //save new parameter
    if (tcsetattr(fd,TCSANOW,&termios_p) != 0)
    {
        printf ("error %d from tcsetattr\r\n", errno);
    }


    printf ("COM%d initailized\r\n",comport);
}

void COMxxx_test_loop(int loop)
{
    char    c;
    int       len=0;
    char    rx_buffer[COM_COM_TEST_BUFFER_LENGTH];
    char    tx_buffer[COM_COM_TEST_BUFFER_LENGTH];
    int     nb_rx_char=0;
    int     result=0;
    struct     timeval tp;
    double     startsecs,secs;
    int        fd1,fd2;
    int        com1,com2,i;
    switch(loop)
    {
        case 1:
            fd1=com_fd1;
            break;
        case 2:
            fd1=com_fd2;
            break;
        case 3:
            fd1=com_fd3;
            break;
        case 4:
            fd1=com_fd4;
            break;
        case 5:
            fd1=com_fd5;
            break;
        case 6:
            fd1=com_fd6;
            break;
        case 7:
            fd1=com_fd7;
            break;
        case 8:
            fd1=com_fd8;
            break;
        default:
            printf("wrong port COM %d\r\n",loop);
            return;
            break;
    }


    //from COM1->COM2
    memset(rx_buffer,0,COM_COM_TEST_BUFFER_LENGTH);
    memset(tx_buffer,0,COM_COM_TEST_BUFFER_LENGTH);
    strcpy(&tx_buffer[0],COM_UCR_RX_TX_TEST_STRING);
    tcflush(fd1,TCIFLUSH);


while (1)
{
    len = read(fd1,&c,1);
    if (len < 1 ) //TODO && errno != EAGAIN)
    {
        printf("Rx error%d: %s\n",com1, strerror(errno));
    }
    else if (len==1)
    {
       printf("Rx %c Ox%x\r\n",c,c);
       break;
    }
}
}

best regards

Hi,

Have you tried code which I have attached early and followed steps ?

HI

yes i have tried this in my initialization function :

    {
        // Object For Struct Termios .
        struct termios options;

        fcntl(fd,F_SETFL,0);
        tcgetattr(fd,&options);
        cfsetispeed(&options,9600);// Function To Set Baud Rate Of Input Stream .
        cfsetospeed(&options,9600);// Function To Set Baud Rate Of Output Stream .
        options.c_cflag |= (CLOCAL | CREAD );// Options For Reading From Devices .
        options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);//Option For Desable Canonical Input .
        options.c_oflag &= ~OPOST;//Option For Desable Canonical Output .
        options.c_cc[VMIN]=1;// Options For Time Outs .
        options.c_cc[VTIME]=10;
        tcsetattr(fd,TCSANOW,&options);// Update Changes .
        //printf("\n Succeeded In  Openning Port : %s\n",a);

    }

thanks