[LinuxPPS] Some help with linuxpps

[Marc Leclerc]

Hi Jeff,

Thanks for your sample, it seems to be working. I adapted your driver to
my platform and seems that loading the driver does the work of creating
the /dev/pps0.

I added a trace to see the irq at work and got

printk(KERN_ALERT "PPS event at %lu.%lu\n", ts.sec, ts.nsec);

PPS event at 1270487590.0
PPS event at 1270487591.0
PPS event at 1270487592.0
PPS event at 1270487593.0
PPS event at 1270487594.0

Hopefully this means something is going right.

Just one more thing, As of know the GPS is plugged into my other
computer as I wait for the hardware to be built. reason is the dev kit
comes with a Serial/USB device so until I get the proper hardware I use
my windows computer for reference in my ntpd.conf

#driftfile /var/lib/ntp/ntp.drift
server 192.168.2.101 

When I do get the gps connected to my own platform could you give me a
few hints on how I should configure my system to achieve best results. 

The GSP will be hooked to ttyS1 therefore I expect some configuration to
be made.


When booting, I would like the ntpd daemon to take the GPS time as is
without regards to the pps indication as so it seems to take a while
until the GPS starts to be accurate. If you have any suggestions on the
matter

What should my ntpd.conf look like in order to take the time from ttyS1,
I just got a scare here, does the trace truly indicate that the time is
being adjusted. 

Well, thanks again for getting me there, appreciated. If you have the
time to fill the last voids it will be appreciated

:) 

On Mon, 2010-03-29 at 16:35 -0400, Jeff Angielski wrote:
> Marc Leclerc wrote:
> 
> > 
> > I plan to use a gpio to connect the PPS pulse to my device PORT G pin 0
> > which can be configured as interrupt if that is required?. It also can
> > be map to /dev/gpio/83, also if required?. Here I cannot solve how to
> > have the device present (do I need an entry in /etc/makedevs.d?) and how
> > to configure the pin (interrupt or input) and the driver to use that
> > gpio. Is there a need for me to do some coding to get the precess going
> > or does the driver take care of this?
> 
> I am struggling trying to make all of this work but I can at least 
> answer this question.
> 
> As a quick hack, just scan /proc/devices and look for the pps device. 
> This will give you your character device major number.  Just manually 
> create the nodes using mknod.  It's a hack but it will get you started. 
>   Later you can get udev to add it automagically.
> 
> You will need to configure it is as interrupt.  Nobody is "polling" the 
> GPIO line.
> 
> Here is a simple IRQ client that I am currently playing with that you 
> may find useful as a starting point.  The driver works but still can use 
> some cleanup.
> 
> 
> 
> *
>   * pps-hwirq.c
>   *
>   *
>   * Based on the ktimer from:
>   * Copyright (C) 2005-2006   Rodolfo Giometti <giometti at linux.it>
>   *
>   *   This program is free software; you can redistribute it and/or modify
>   *   it under the terms of the GNU General Public License as published by
>   *   the Free Software Foundation; either version 2 of the License, or
>   *   (at your option) any later version.
>   *
>   *   This program is distributed in the hope that it will be useful,
>   *   but WITHOUT ANY WARRANTY; without even the implied warranty of
>   *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>   *   GNU General Public License for more details.
>   *
>   *   You should have received a copy of the GNU General Public License
>   *   along with this program; if not, write to the Free Software
>   *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>   */
> 
> 
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/init.h>
> #include <linux/time.h>
> #include <linux/timer.h>
> #include <linux/pps_kernel.h>
> #include <linux/irq.h>
> #include <linux/interrupt.h>
> 
> /*
>   * Global variables
>   */
> 
> /* TODO: Make a module parameter and leave this as default */
> #define PPS_HWIRQ_DEFAULT	6
> static unsigned int pps_hwirq = PPS_HWIRQ_DEFAULT;
> 
> /* TODO: Make a structure to share all of this */
> static unsigned int pps_virq;
> static int source;
> 
> /*
>   *
>   */
> static irqreturn_t pps_hwirq_handler(int irq, void *parm)
> {
> 	struct timespec __ts;
> 	struct pps_ktime ts;
> 
> 	/* First of all we get the time stamp... */
> 	getnstimeofday(&__ts);
> 
> 	/* ... and translate it to PPS time data struct */
> 	ts.sec = __ts.tv_sec;
> 	ts.nsec = __ts.tv_nsec;
> 
> 	pps_event(source, &ts, PPS_CAPTUREASSERT, NULL);
> 
> 	pr_debug("PPS event at %lu\n", jiffies);
> 
> 	return IRQ_HANDLED;
> }
> 
> /*
>   * The echo function
>   */
> 
> static void pps_hwirq_echo(int source, int event, void *data)
> {
> 	pr_info("echo %s %s for source %d\n",
> 		event & PPS_CAPTUREASSERT ? "assert" : "",
> 		event & PPS_CAPTURECLEAR ? "clear" : "",
> 		source);
> }
> 
> /*
>   * The PPS info struct
>   */
> 
> /* TODO: Decipher the needed flags */
> static struct pps_source_info pps_hwirq_info = {
> 	.name		= "pps_hwirq",
> 	.path		= "",
> 	.mode		= PPS_CAPTUREASSERT | PPS_OFFSETASSERT | \
> 			  PPS_ECHOASSERT | \
> 			  PPS_CANWAIT | PPS_TSFMT_TSPEC,
> 	.echo		= pps_hwirq_echo,
> 	.owner		= THIS_MODULE,
> };
> 
> /*
>   * Module staff
>   */
> 
> static void __exit pps_hwirq_exit(void)
> {
> 	free_irq(pps_virq, NULL);
> 
> 	pps_unregister_source(source);
> 
> 	pr_info("hwirq PPS source unregistered\n");
> }
> 
> static int __init pps_hwirq_init(void)
> {
> 	int ret;
> 
> 	pps_virq = irq_create_mapping(NULL, pps_hwirq);
> 	if (pps_virq == NO_IRQ) {
> 		printk(KERN_ERR "cannot create irq mapping for hw irq: %d\n", pps_hwirq);
> 		return -EINVAL;
> 	}
> 
> 	/* TOOD: Do we need to pass anything into the handler? */
> 	ret = request_irq( pps_virq, pps_hwirq_handler, IRQF_TRIGGER_RISING, 
> "pps hwirq", NULL);
> 	if (ret) {
> 		printk(KERN_ERR "failed to register handler for virq: %d\n", pps_virq);
> 		return ret;
> 	}
> 
> 	ret = pps_register_source(&pps_hwirq_info,
> 				PPS_CAPTUREASSERT | PPS_OFFSETASSERT);
> 
> 	if (ret < 0) {
> 		printk(KERN_ERR "cannot register hwirq source\n");
> 		return ret;
> 	}
> 	source = ret;
> 
> 	pr_info("hwirq PPS source registered at %d\n", source);
> 
> 	return  0;
> }
> 
> module_init(pps_hwirq_init);
> module_exit(pps_hwirq_exit);
> 
> MODULE_AUTHOR("Jeff Angielski <jeff at theptrgroup.com>");
> MODULE_DESCRIPTION("Hardware interrupt PPS source");
> MODULE_LICENSE("GPL");
> 
> 
>