Rob wrote:
David Lord <[email protected]> wrote:
Rob wrote:
I would like to use the Atom driver (22) on a Linux system with a
parallel port. It is not clear to me from the scattered info I have
found on internet if this is going to work.
Using a modern Linux kernel with the PPS module, is it possible to
symlink /dev/pps0 to a parallel port device and then connect the PPS
signal to the ACK input (pin 10)?
If not, what else is required to get this working?
Examples always refer to the use of a serial port DCD input, but for
best accuracy (in the microsecond range) I think the parallel port
is better.
(no RS232 drivers/receivers, no funny UART that may delay interrupts)
Any other suggestions for an accurate PPS input?
On NetBSD with stock ntpd, pre 2010, I did comparisons of
pps from Sure GPS with output from dcd at ttl level vs the
"serial" dcd but didn't really see any consistent difference.
Did you try the parallel port?
I am interested not only in jitter but also in any constant offset
between the PPS pulses and system time on different systems (possibly
using different makes of serial card). 4-6 us would be good enough for
my purpose, but it would not be good when one system had a 10us offset
because of a propagation delay in a linedriver/receiver.
Yes, and from archived ntp.conf at that time /dev/pps* at ppbus
but I also tried without ppbus and had a symlink to /dev/lpt*
For past couple of years I have pps2 -> /dev/tty00 and there
is no ppbus in my recent kernels so I guess it was from a
custom kernel.
David
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