Rockwell Automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User Manual - Manual (Page 123)

Chapter 7
Using the Serial Ports
7-15
* EXAMPLE: int path;
* char out_data[3];
* int cnt = 3;
* path = open(“/t1”, (S_IREAD | S_IWRITE));
* init_485(path);
* status = write_485(path, out_data, cnt)
* if (status == -1)
* exit();
****************************************************************************/
int write_485(path, buffer, count)
int path;
char *buffer;
int count;
{
int tmp_count; /* Temporary count variable */
int status; /* Status variable */
int size; /* Size of leftover stuff in input buffer */
int watchdog; /* Watchdog counter variable */
char tmp_buff[256]; /* Temporary buffer to clear input port */
char buff; /* Character buffer */
int sent; /* Actual number of characters sent */
/*** Make sure buffer is empty ***/
if ((size = _gs_rdy(path)) != -1) /* Is it empty? */
{
while (size--)
if ((status = read(path, &buff, 1)) == -1) /* Clear it out */
{
fprintf(stderr, “**** ERROR reading input buffer! ***\n”);
return(-1);
}
}
/*** Enable the transmitter ***/
if ((status = _ss_dsrts(path)) == -1)
{
fprintf(stderr, “**** ERROR turning on transmitter ***\n”);
return(-1);
}
/*** Send the data ***/
if ((sent = write(path, buffer, count)) == -1)
{
fprintf(stderr, “**** ERROR writing data ***\n”);
return(-1);
}
/*** Watch the data going out. When the input buffer has the same ***/
/*** amount as sent, then the transmitter can be turned off ***/
tmp_count = 0;
watchdog = 50000; /* This is worst case, it may be reduced based */
/* on baud rate and number of characters sent. */
while ((tmp_count < sent) && watchdog--)
tmp_count = _gs_rdy(path);