[LinuxPPS] Trying to get parallel port client working on 2.6.26

[Paul Simons]

I have an old TrueTime 4<mumble>-DC that uses a GPS to GOES converter. 
I've been a member of pool.ntp.org for some time now, and I'd like to get
more accurate and get PPS running.  This clock puts out a TTL PPS.  First
question:

I notice that people seem to convert from TTL to RS232 and then use the
serial port.  Why is that?

I am using the parallel port (pin 10 - ACK, pin 24 - ACK ground) and just
going straight TTL.  Everything seems to register fine:

dmesg | grep -i pps
LinuxPPS API ver. 1 registered
PPS line discipline registered
new PPS source parport0 at ID 0
parport_pc 00:08: PPS source #0 "/dev/lp0" added
dmesg | grep -i parport
parport_pc 00:08: reported by Plug and Play ACPI
parport0: PC-style at 0x378 (0x778), irq 7, dma 3
[PCSPP,TRISTATE,COMPAT,ECP,DMA]
lp0: using parport0 (interrupt-driven).
new PPS source parport0 at ID 0
parport_pc 00:08: PPS source #0 "/dev/lp0" added

However, no joy:

./ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
time_pps_fetch() error -1 (Connection timed out)
time_pps_fetch() error -1 (Connection timed out)
time_pps_fetch() error -1 (Connection timed out)
^C

I am using a Debian kernel:

uname -a
Linux mercury 2.6.26.simonet #1 SMP Sat Sep 13 11:10:50 PDT 2008 i686
GNU/Linux

and I am using the ntp-pps-2.6.26.diff patch.

I'd like to see this working as a first step.  Is that reasonable?  Should
I start sprinkling printks to see where I'm going wrong?  I hooked up a
digital multimeter and it twitches; should I get some sort of LED?  Should
I convert to RS232 signaling?

Okay, I'll stop now.

-- 
Paul Simons
Covington, WA, USA