Re: [gpsd-dev] Has anybody tried the SiRF S4?

[Michael Tatarinov]

Hello

2014-03-12 10:30 GMT+04:00, Hal Murray <address@hidden>:
>
> I saw a comment about them someplace so I ordered one.
>
> I'm testing a GlobalSat BU-353S4  (USB)
> So far, not great.
>
> It's a bit more sensitive than a SiRF 3 in a similar location.
>
> Playing with gpsmon, I can't get it to change baud rate.
> It often ends up non-responsive:
>   Neither gpsmon nor gpsd will talk to it.
>   Power cycle fixes things.
>
> I think I saw a similar problem when trying to switch from SiRF binary to
> NMEA.
>
> It starts at 4800, NMEA.
> gpsmon can switch to SiRF mode.
> gpsd/ntpd/shm only gets 1/2 to 3/4 of the samples.
>
> Is SiRF mode, gpsmon says:
>   Grumph, now that I want to cut/paste, I can't get it to show the firmware
>
> version.
> Finally got one:
> ?^FGSD4e_4.0.4-P1_RPATCH.07-GS008-F-GPS-4R-1201128 01/12/2012 012
>
> In SiRF mode, I haven't seen any data in the the block in the lower-right,
> DGPS Status.
>
> I assume part/most of the problem is due to the lower baud rate.

SiRF 3 is broken. I opened PR https://savannah.nongnu.org/bugs/?41719
As workaround I wrote patch http://z.grey.net.ru/gpsd-SiRF-workaround.patch

> How does gpsmon decide to poll for the Firmware Version?
> Is there any key I can use to get it to try again?
> (Are there other packet types only polled occasionally?)

gpsmon requests FW version on initialization.
You can try to send FW request (0x84 0x00) via gpsmon 'x' command.

> In SiRF mode, the lower left block of gpsmon says Measured Tracker, Packet
> Type 4.
> The two rightmost column are labeled "?" and "SF".
> What do they mean?
>
> With a SiRF 3, I see occasionally Ts in the ? column and nothing in the SF
> column.
> With the SiRF 4, I see similar Ts and some 2 digit numbers in the SF column,
>
> but they get rewritten to blanks frequently and, after a delay, filled in
> again slowly.  (Seems like more than a single packet type.)

'T' in column '?'  means that bit 1 in state field Message ID 0x04 sets.
for SiRF docs:
"Bit 1 set means that the phase relationship between the I and Q
samples is being tracked. When this bit is cleared, the carrier phase
measurements on this channel are invalid."
http://git.savannah.gnu.org/cgit/gpsd.git/tree/monitor_sirf.c#n339

SF is SubFrame (50bps data). In this column prints PRN for which
subframe data were obtained.
http://git.savannah.gnu.org/cgit/gpsd.git/tree/monitor_sirf.c#n397