[LinuxPPS] Debugging the pps

[Hal V. Engel]

On Friday, April 29, 2011 04:07:34 PM Marc Leclerc wrote:
> Hi,
> 
> When the PPS system starts, how does it goes about finding PPS sources?
> We have gone right to the soc (vortex86DX) DCD pin for a signal and its
> there so the interrupt on IRQ3 (ttyS1) is getting there and is shown
> incrementing in /proc/interrupt. but beside the messages at boot there
> is no sign at all of the subsystem. even with debugging enabled...
> should there not be at least a log entry pass boot that its trying
> something? I had that working on our old board ok (arm based with a GPIO
> driver) but on this one I am clueless as of now
> 
> Thanks

You need to setup line discipline for your device.  I do this in an ntp 
startup script that wraps the standard system startup script for ntp that 
looks like this:

 #!/sbin/runscript
depend() {
        need net
        use dns logger
        after  ntp-client
}

start() {

        ebegin "Starting custom ntpd"

        ldattach PPS /dev/ttyS1

        sleep 2 # give ppsldisc and udev time to get settled

        /etc/init.d/ntpd start
}

stop() {
        ebegin "Stopping custom ntpd"
        /etc/init.d/ntpd stop
}


> 
> On 2011-04-27 17:10, Marc Leclerc wrote:
> > Hi,
> > 
> > I did the check and we do get the interrupt on IRQ3 every second with
> > the Rx/Tx deconnected from the gps. still no log pass the PPS line
> > discipline registered. still no entry in /sys/class/pps/.
> > 
> > I would hope that with debugging output enabled there would be sing of
> > life... or death.
> > 
> > Any other suggestions or next step woudl be appreciated
> > 
> > Thanks
> > 
> > On 04/26/2011 07:16 PM, Bernhard Schiffner wrote:
> >> Am Dienstag, 26. April 2011, 21:25:16 schrieb Marc Leclerc:
> >>> Hi,
> >>> 
> >>> I have moved to a new board x86 based and compiled kernel 2.6.34.7 with
> >>> pps support + line discipline. I have a gps module hooked to ttyS1 +
> >>> the pps to pin 1 DCD. We checked the pps signal with a scope and it
> >>> does get to the pin.
> >> 
> >> First: Is this real RS232 level or some "pseudo" (5V, 3.3V)?
> >> Second: Is the pulse long enough to be catched by interrupt controllers
> >> (>70µs)?
> >> 
> >> Next: A 8250 (or similar) interrupts on DCD-change. Do you see "advance"
> >> of the according interrupt in /proc/interrupts while RxD is
> >> disconnected? ( pps / line_discipline is a level above that.)
> >> 
> >>> when the kernel boots I do see the message that pps line
> >>> discipline is registered. I did create the pps device + links for ntp.
> >>> as for the gps it does work ok with ntp.
> >> 
> >> So this part seems ok.
> >> 
> >>> problem is there is no sign of
> >>> pps at all. the /sys/class/pps is empty and there are no messages
> >>> appering in the logs (dmesg) that the pps is doing anything beside
> >>> being registered.
> >> 
> >> What hardware / kernelmodul (*.ko) do you speak about?
> >> I'am not quite sure, if pps is implemented for all "freaky" serial
> >> drivers. 8250/16550 should work.
> >> 
> >>> I have also enabled debugging support but no further sign.
> >>> Also tried the patch for kernel consumer. Any clue on the steps I could
> >>> take to find what's wrong.
> >>> 
> >>> Regards
> >> 
> >> Hope it helps to make you sure about "hardware" first.
> >> 
> >> 
> >> Bernhard
> >> 
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> > 
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