Rockwell Automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User Manual - Manual (Page 120)

Chapter 7
Using the Serial Ports
7-12
Example Code for RSĆ485 Communication
/*****************************************************************************
* i n i t _ 4 8 5 . c
* PURPOSE: Initialize the coprocessor’s serial port for generic serial
* communication using RS-485.
* REVISION LOG: 4/12/94 Original release of program
* 6/30/94 Turned off psc character
* USAGE: This function initializes the serial port properly for doing
* generic RS-485 communication to a coprocessor serial port. The
* function is passed the path of the port. This function then
* turns off all the default terminal settings that may adversely
* effect communications later on. A 0 is returned upon success and
* a -1 if there was a problem. Check the global variable errno
* for the error code reported.
* SYNOPSIS int init_485(path)
* int path; - Path number from opened port
* EXAMPLE:
* path = open(“/t1”, (S_IREAD | S_IWRITE));
* status = init_485(path);
* if (status == -1)
* exit();
****************************************************************************/
/* system include files */
#include
#include
int init_485(path)
int path;
{
char buff; /* Character buffer */
int status; /* Status variable */
int size; /* Size of leftover stuff in input buffer */
struct sgbuf opts; /* Buffer for path descriptor information */
/*** Get the current options ***/
if ((status = _gs_opt(path, &opts)) == -1)
{
fprintf(stderr, “**** ERROR on getting port options! ***\n”);
return(-1);
}
/*** Set the options. This section is not needed with firmaware rel. A/E and later***/
opts.sg_pause = 0; /* Screen pause to off*/
opts.sg_psch = 0; /* No pause character */
opts.sg_bspch = 0; /* No backspace character */
opts.sg_dlnch = 0; /* No delete line character */
opts.sg_rlnch = 0; /* No reprint line character */
opts.sg_dulnch = 0; /* No duplicate last line character */
opts.sg_tabcr = 0; /* No tab character */
opts.sg_echo = 0; /* Echo off */
opts.sg_eorch = 0; /* Ignore end of record */
opts.sg_eofch = 0; /* Ignore end of file */
opts.sg_kbach = 0; /* Keyboard abort off - default = CTRL-E */
opts.sg_kbich = 0; /* Keyboard quit off - default = CTRL-C */
opts.sg_xon = 0xff; /* XON turned off, 0xff is special code for*/
opts.sg_xoff = 0xff; /* copro RS485, it will not interpret 0xff */
opts.sg_parity = 0x00; /* No Parity, 8 Bits, 1 Stop Bit, See below */
opts.sg_baud = 0x0e; /* Baud rate at 9600, See below