Re: [gpsd-dev] Initialization & probing questions

[Kai Harrekilde-Petersen]

Hi Gary,

On 26-03-2018 23:44, Gary E. Miller wrote:
> Yo Kai!
>
> On Mon, 26 Mar 2018 22:28:59 +0200
> Kai Harrekilde-Petersen <address@hidden> wrote:
>
> > I'm trying to implement the Skytraq driver the 'right way', going by
> > the comments in driver_proto.c and referencing the Ublox driver.
> Why not build on the existing Skytraq driver?  It works for Venus 6.
I did, and I do, but the existing driver was missing a several things 
(including not detecting my GPS and it had no way to configure it 
through gpsctl) so I was beginning to rewrite parts of it.
I've now added bin/nmea mode, cycletime and baudrate handling to it.
> > 1) If I send a command, how should I wait for the response before
> > returning?
> You don't, can't, should not.
Good, this is what I expected.
> > 3) Excessive probing time.
> > Since the Skytraq powers up at 115.200 baud, it takes an obscene
> > amount of time for it to be probed (as  584 sec. Yes, almost 10 min!).
> Which is why we always recommend to set the GPS to the right serial
> port speed before starting gpsd.
> stty -F /dev/ttyS0 115200
Ah, I must have missed that memo. I found that stty command myself just 
the other day, but wanted to make sure I wasn't missing something obvious.
> > 4) Store/restore of device settings.
> > The skytraq allows to to probe its settings to hearts' content, which
> > allows me to restore the state when deactivating.
> You could, but then that makes other things hard.  I prefer to just leave
> the GPS as is on exit.  Makes debugging easier.  Opinions vary.

Good. Less work :)

The modified driver should work for both the Venus6 & Venus8 now. Do you 
want patches directly for testing on the Venus6 or should I post them to 
the list?

One question related to gpsd.h: I noticed that SKY_PACKET is placed at 
the end (20), but from looking at the other macros, it looks like it 
should be SKY_PACKET <= MAX_GPSPACKET_TYPE, otherwise it won't be picked 
up by GPS_PACKET_TYPE(n) and missed by PACKET_TYPEMASK(n) and GPS_TYPEMASK.
I changed SKY_PACKET to 16 and bumped the following and at least for the 
Skytraq it works correctly.

Best regards,

Kai