In article <slrnis0nra.4on.un...@wormhole.physics.ubc.ca>, un...@wormhole.physics.ubc.ca says... > > On 2011-05-03, David J Taylor <david-tay...@blueyonder.co.uk.invalid> wrote: > >> As the OP who started this (long and sometimes ammusing) thread... > >> > >> I do carry a GPS receiver with me, but sadly not PPS capable, I use it > >> for location determination/tracking/navigating etc. Maybe I should > >> include a GPS18 or 16 in the already bulging Laptop bag I lug arround. > > > > Even better if there were on on a USB stick, and you had a handy USB > > extension lead! > > Unfortunately , AFAIK, usb is terrible for delivering a PPS-- ie no > interrupt lines-- the problem with having only two data lines (one beign > signal ground) > . > > > > > > How critical is your time need? If it's within minutes, then the PC's > > clock is likely good enough. If it's in the UK or Europe, I would be > > surprised if pool servers did not get you well within the second - perhaps > > within 100msec - particularly if you set the servers based on the country > > you're in. I suspect that if you need closer than tens of milliseconds, > > carrying round a GPS 18x LVC (which I jokingly suggested) may actually be > > necessary. NTP was designed when connections were nothing like as good as > > they are now, and is supposedly robust in those circumstances. It is > > designed for 24-hours operation, though. > > > > 73, > > David > >
Two data line's, plus ground and 5V power. The data lines form a bidirectional diferential data bus, with a protocol more like a network than anything else. For low speed devices, there are bitbanged firmware routines about for the likes of the Atmel single chip devices, if it interests you. http://www.obdev.at/products/vusb/index.html I digress... DaveB _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
