[LinuxPPS] Debugging the pps

[Bernhard Schiffner]

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