Re: [Thumbgps-devel] Project clarification

[Patrick Maupin <pmaupin@gmail.com>]

On Tue, Mar 13, 2012 at 10:05 PM, tz <tz2026@gmail.com> wrote:

> 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.

I was definitely thinking of this when thinking of building the
FPGA-based timestamp-everything unit.  You're right that if we're
willing to write USB device firmware, a lot of opportunities to gain
tighter tolerances present themselves.  This would be even more true
if we pick a highspeed device.

Another simple thing we could do with basic serial units is to loop
back RTS to CTS so you can calculate round-trip time to put an upper
bound on inbound delay.

If we really want to consider our own firmware, we might consider
something like nuttx running on either an Atmel part or an NXP
LPC3131.  Olimex has an NXP development board for $90.