Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!hplabs!hpfcdc!hpfcmgw!rdg
From: rdg@hpfcmgw.HP.COM (Rob Gardner)
Newsgroups: comp.sys.hp
Subject: Re: HELP needed with GPIO interface
Message-ID: <1080057@hpfcmgw.HP.COM>
Date: 6 Jun 89 18:46:44 GMT
References: <52@eutnv1.UUCP>
Organization: HP Fort Collins, CO
Lines: 36


>  We are designing an interface between the 98622A GPIO interface in
> our HP9000-330 computer (HP-UX 6.2) and a bus system that was developed

> 		char character;
> 
> 		gpio_dev = open("/dev/gpio", O_RDWR);

Check the return value from the open. This could easily fail!!

Also, if you are writing one char at a time, add in:

		io_width_ctl(gpio_dev, 8);	/* need to link w/ -ldvio */
		io_reset(gpio_dev);		/* usually a good idea */

> 		for (i = 0; i < 1000000; i++)
> 		{
> 			write(gpio_dev, character, sizeof(char));
                                        ^^^^^^^^^

You need &character here to get the correct data out. You're lucky this
doesn't simply core dump. Check the return value here also.

> and use a bus monitor to simulate handshaking manually, the first
> write() doesn't wait for the PFLG to become low but the second does.

Check the senses of the handshake switches on the 98622 card, as they
can affect the logic.

 
    Rob Gardner                     hplabs!hpfcmr!rdg
    Hewlett Packard                 or rdg%hpfcmr@hplabs.hp.com
    Fort Collins, Colorado          303-229-2048
		80525-9599

		     "Ask me about Home Brewing"