Re: GPS reciever for cubetruck

[Greg Troxel <gdt%lexort.com@localhost>]

Many receivers in the $20-$50 range have real serial and a TTL-level (or
CMOS level) PPS line, ttat can be hooked to a serial control line or
GPIO.  However, if you calibrate the delay against the net, and then run
with it, you can get sub 5 ms.

The only USB device I have seen with PPS is the "GR601W", a special run
with pps brought out to a modem control line on the USB/serial chip, and
that gets about 1 ms fuzz to interrupts.   I do not believe these are
obtainable now.