[ts-7000] Re: TS7260-Reading from /dev/ttyUSB0

["tsao.terence" <>]

Hi Alexey,

   Thanks for the help, I like the code which you provided.  But I am still 
getting the same result.  After more testing, and printing out the packet that 
I received, I found out for a 520 bytes packet, I am only receiving 264 bytes 
from it.  I lost 256 bytes from the packet.

The lost bytes problem only occurs if the ttyUSB0 baudrate is higher than 38400 
bps

for example:
9600baud, result: sent 520, successfully received 520
36400baud, result: sent 520, successfully received 520
57600baud, result: sent 520, but only received 256
115200baud, result sent 520, but only received 256
500000baud, result sent 520, but only received 256

I don't know why the problem is so consistent, has someone had experiences like 
this before?  

Here is my receiving packet code:
unsigned char receivePacket(int fd, unsigned char *buffer)
{
    printf("Receive Packet\n");
    unsigned int i=0;
    unsigned int left_to_read=520;
    while(left_to_read>0)
    {
     unsigned char temp = read(fd, buffer+i, left_to_read);
     usleep(10);
     i+=temp;
     left_to_read-=temp;
    }
    for (i=0; i<520; i++)
    {
     printf("%c", buffer[i]);
    }
    return 0;
}

Here is how I open the port:

int openUSB()
{
    //system("stty -F /dev/ttyUSB0 57600 cs8 -cstopb -parity -icanon min 1 time
    int fd = open ("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY | O_FSYNC);
    if (fd==-1)
    {
      fprintf(stderr, "open_port: Unable to open /dev/ttyUSB0 -%s \n",
               strerror(errno));
    }

    struct termios options;

    /*Configure port reading*/
    fcntl (fd, F_SETFL, FNDELAY);
    /*Get the current options for the port*/
    tcgetattr(fd, &options);

    /*Set baudrate to 500000Mb*/
    cfsetispeed(&options, B57600);
    cfsetospeed(&options, B57600);

    /*Mark the character size to 8 bits, no parity*/
    options.c_cflag     |= (CLOCAL | CREAD);
    options.c_lflag     &= ~(ICANON | ECHO | ECHOE | ISIG);
    options.c_oflag     &= ~OPOST;
    options.c_iflag     &= ~(IXON | ICRNL);
    options.c_cc[VMIN]  = 0;
    options.c_cc[VTIME] = 0;
    tcsetattr(fd, TCSANOW, &options);
    return fd;
}



--- In  Alexey Vdovin <> wrote:
>
> Tsao,
> 
> In function receivePacket try read more then 1 byte at once:
> 
> unsigned char temp = read(fd, buffer+i, left_to_read);
> i += temp;
> left_to_read -= temp;
> 
> To avoid hangs add read timeout to this function.
> Keep in mind, some date bytes may be lost or corrupted during 
> transmission, you need error checking mechanism.
> 
> ---
> Best Regards
> Alexey Vdovin
> 
> -----Original Message-----
> From: "tsao.terence" <>
> To: 
> Date: Thu, 04 Mar 2010 08:44:03 -0000
> Subject: [ts-7000] TS7260-Reading from /dev/ttyUSB0
> 
> > Dear Linux masters,
> > 
> >      I am communicating TS7260 with my sensor device using a USB to serial 
> > FTDI converter.  The sensor uses the uart interface, and the TS7260 uses 
> > the USB interface.  The sensor device will send TS7260 a packet of data 
> > which contains 512 bytes, aka each packet is 512 bytes.
> > 
> > 
> > I had success reading from ttyUSB0 with 9600 and 38400 baudrate, but when I 
> > jump to 57600 baud, the program just hangs.  I think there might be 
> > something wrong as I open the USB port, or my receive function has too much 
> > software overhead.  Anyone here had success reading from the ttyUSB0 port?
> > 
> > Here is my open USB function:
> > int openUSB()
> > {
> >     int fd = open ("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY | O_FSYNC);
> >     if (fd==-1)
> >     {
> >       fprintf(stderr, "open_port: Unable to open /dev/ttyUSB0 -%s \n",
> >                strerror(errno));
> >     }
> > 
> >     struct termios options;
> > 
> >     /*Configure port reading*/
> >     fcntl (fd, F_SETFL, FNDELAY);
> >     /*Get the current options for the port*/
> >     tcgetattr(fd, &options);
> > 
> >     /*Set baudrate to 500000Mb*/
> >     cfsetispeed(&options, B57600);
> >     cfsetospeed(&options, B57600);
> > 
> >     /*Mark the character size to 8 bits, no parity*/
> >     options.c_cflag     |= (CLOCAL | CREAD);
> >     options.c_lflag     &= ~(ICANON | ECHO | ECHOE | ISIG);
> >     options.c_oflag     &= ~OPOST;
> >     options.c_iflag     &= ~(IXON | ICRNL);
> >     options.c_cc[VMIN]  = 0;
> >     options.c_cc[VTIME] = 0;
> >     tcsetattr(fd, TCSANOW, &options);
> >     return fd;
> > }
> > 
> > Here is my read function:.
> > unsigned char receivePacket(int fd, unsigned char *buffer)
> > {
> > 
> >     unsigned int i=0;
> >     unsigned int left_to_read=520;
> >     unsigned char byte;
> >     while(left_to_read>0)
> >     {
> >      nsigned char temp = read(fd, &byte, 1);
> >      if(temp>0)
> >      {
> >       left_to_read--;
> >       buffer[i]=byte;
> >       printf("%.2x",byte);
> >       i++;
> >      }
> >     }
> >     return 0;
> > }
> >
>




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