Re: [Thumbgps-devel] Project clarification

[tz <tz2026@gmail.com>]

A few other observations:

Many of the SoCs used in the cheap routers have other on-chip
perhpherals which can get us past the USB.  I think I can get an
Atmega to be a time-source synced to UTC.

We could send an event OUT the USB host and timestamp it at the
device, returning when it saw it - this might be more accurate if this
is more granular than polling.

We don't know yet if LinuxPPS - kernel interrupt driven timestamping
is needed, but will probably be much more precise.

No one has suggested turning this into a time peripheral, but that
might be easier - if a microcontroller could be synced and made
accurate enough (varactor like the old Heathkit clocks?) then all the
gettime calls could go out to our device and get precise time.  Of
course the kernel could sync its time easily as well.

There are faster than PPS, e.g. the Garmin 18LVx-5Hz has 5 pulses per
second, at each 200mS interval, one of the 5 is the precise UTC, the
others are precise too.

The Sparkfun module plus either active antenna that goes with it makes
it easy to receive GPS - having a dongle with a small strip antenna
that you have to fiddle a lot with to get a good signal defeats the
purpose.  The magnetic mounts with long cables make things easy.  We
haven't talked much about antennas, but it is important.