/* Demonstration program:  parallel poll of HP-IB (IEEE-488) device
 * J. M. Anderson, F&M College, 1989.
 *
 * Only the function "process" is shown; other functions are very similar,
 * or identical, to their counterparts in "tablspoll.c"
 */

int process()
{
	/* Process the interrupt.
	 * This function is called when an interrupt
	 * is detected on the bus.
	 *
	 * For the purpose of this demo, SRQ must be asserted by the
	 * tablet for pen press or menu pick.
	 */
	 
	int bstatus, tstatus;	/* bus status, tablet status */
	int x, y, p, k;			/* pen position, menu key */
	
	/* See if interrupt was caused by the tablet.  Perform parallel poll.
	 * The tablet will assert line 1 whose value is 2 when its address is
	 * 06; all of this is fixed in the tablet's hardware.  Therefore,
	 * we should look for a response to the parallel poll whose value is
	 * 2.
	 */
	ieeewt("ppoll\n");
	ieeescnf("%d", &bstatus);
	if (bstatus == 2)			/* response from tablet */
	{
		/* Serial-poll the tablet to find its status;
		 * We know that it is the tablet which caused the interrupt;
		 * all we need to do now is find out why.
		 */
		ieeewt("spoll 06\n");
		ieeescnf("%d", &tstatus);
		if PENPRESS
		{
			ieeewt("output 06;OD\n");
			ieeewt("enter 06\n");
			ieeescnf("%d,%d,%d",&x, &y, &p);
				/* beep high for stylus press on tablet */
			ieeewt("output 06;BP 48,150,4\n");
			printf("\ndigitized point: %d %d\n",x, y);
			return(0);
		}
		
		if MENUPICK
		{
			ieeewt("output 06;RS1\n");
			ieeewt("enter 06\n");
			ieeescnf("%d", &k);
				/* beep low for stylus press on menu square */
			ieeewt("output 06;BP 8,150,4\n");
			printf("Menu square %d touched.\n", k);
			return(1);
		}
	}
}