Re: [Thumbgps-devel] Build vs. modify vs. what should we be doing anyway?

[Dave Taht <dave.taht@gmail.com>]

On Tue, Mar 13, 2012 at 4:54 AM, Eric S. Raymond <esr@thyrsus.com> wrote:
> Dave Taht <dave.taht@gmail.com>:
>> On Mon, Mar 12, 2012 at 7:13 PM, Eric S. Raymond <esr@thyrsus.com> wrote:
>> > Chris Kuethe <chris.kuethe@gmail.com>:
>> >> ublox antaris4 (and probably everything newer) has on-die usb and
>> >> implements the abstract modem class. but 1PPS isn't transmitted over
>> >> usb.
>> >
>> > Annoyingly, it probably could be.  That modem model pretty much has to have
>> > DCD and RI events.
>>
>> Perhaps simply a real usb microcontroller with spi or i2c then driving
>> usb-2.0 for real...
>
> So, how would we get the data off the GPS chip if not through the TTL-level
> serial interface?  Are you proposing building our own serial-to-USB adaptor
> with a microcontroller?

Proposing, not as yet. Researching the idea, yes.

1) It would be my hope that the blox UBX-G6010-ST-TM actually did
supply the PPS over it's existing USB interface. The specs are
otherwise quite ideal - single satellite operation, fixed location
operation, 15ns pulse, etc., as you'll see from the links provided
earlier. eval board here:

http://www.abacuscity.ch/abashop?s=142&p=productdetail&sku=114

But I figure an email or conversation with u-blox is in order
regarding the level of their pps support and
firmware. If portions of their firmware were hackable, that would be excellent.

2) If it didn't, interfacing the time pulse pin of nearly any hardware
with a microcontroller that that had a full usb stack (eg the AVR
mentioned earlier) offers the opportunity to offer gps over a
non-serial, saner-for-gps new usb interface, no need to emulate
rs-232...

This latter idea has some good points (not all that much more
expensive than a usb-serial chip!), and
bad (whole other cpu, when there's a perfectly good arm7 inside most
of these gps chips)

> --
>                <a href="http://www.catb.org/~esr/">Eric S. Raymond</a>



-- 
Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608
http://www.bufferbloat.net