Re: RS485/COM2 Error in SBC84500 documentation

From: Frencia (jean.pierre.frencia_at_wanadoo.fr)
Date: 06/20/05 

Date: Mon, 20 Jun 2005 21:17:49 +0200

Hi

There is an error in the SBC84500 documentation concerning RS485/COM2 pins
assignment.
The signal is between pin 1 (DATA-) and pin 2 (DATA+) instead of pin 1 and
pin 3 as stated page 29 of the documentation.

I also have removed CRTSCTS flag when tuning the termios.

Here is my OpenDevice routine (if it could be helpful for somebody else).

int OpenDevice (char* device)
{
  int fd;

  fd = open(device, O_RDWR | O_NOCTTY );
  if(fd<=0) {
    fprintf(stderr, "Error opening %s\n", device);
    exit(-1);
  }
  tcgetattr(fd,&oldtio); /* save current port settings */
  tcgetattr(fd,&newtio); /* get current port settings */
  newtio.c_cflag = BAUDRATE | CS8 | CLOCAL | CREAD;
  // BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD does NOT work
  newtio.c_cflag &= ~PARENB; /* no generation of parity bit */
  newtio.c_cflag &= ~CSTOPB; /* 1 Stop bit */
  newtio.c_iflag &= ~INPCK; /* no input parity check */
  newtio.c_iflag = IGNPAR;
  newtio.c_oflag = 0;

  /* set input mode (non-canonical, no echo,...) */
  newtio.c_lflag = 0;

  newtio.c_cc[VTIME] = 10;
  newtio.c_cc[VMIN]= 0;

  tcflush(fd, TCIFLUSH);
  tcsetattr(fd,TCSANOW,&newtio);
  return(fd);
}

Grant Edwards wrote:

> On 2005-06-18, Frencia <jean.pierre.frencia@wanadoo.fr> wrote:
>
>> I'm trying to use the RS485/COM2 port on an embedded Axiom
>> SBC84500 card running kernel 2.4.26. I have configured the
>> JP9,JP10,JP10 according to the documentation but there is no
>> output signal when writing to /dev/ttyS1.
>
> You might have to assert RTS in order to enable the RS-485
> drivers.
>
>> I read somewhere that I should use ioctls to write to the port
>> instead of the standard write function.
>
> I really doubt that. I've been doing serial stuff under Unix
> for 15 years, and I've never heard of using ioctl() to write
> data to a serial port.
>

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