Ideas for a cheap GpsD device

Posted by: siberia37

Ideas for a cheap GpsD device - 03/06/2004 13:52

I've been looking for ideas on finding a cheap device that could run some kind of linux and GpsD. Basically this means the device must have a serial port, ethernet port and be able to be hacked easily to run linux. The goal here is to have a device where I can hook my Gps up to it, hook the ethernet port to the empeg, and then point GpsApp to the device as an GpsD source, thus freeing up the empeg's serial port in the car.
I've been reading a lot on SeattleWireless looking for devices to hack to run Linux and the Linksys WRT54g looks promising, two serial ports can be modded onto it, but it's relatively expensive and would be kind of a waste of a 802.11g router to keep it in my car all the time. There are some other 802.11b routers that can be hacked, but they look kind of difficult to deal with. Does anyone have any other ideas for devices I could use to run GpsD with?
Posted by: tfabris

Re: Ideas for a cheap GpsD device - 03/06/2004 13:54

That's gotta be the most convoluted idea for a hack I've ever heard of.

So why such importance to free up the empeg serial port?
Posted by: siberia37

Re: Ideas for a cheap GpsD device - 03/06/2004 14:08

In reply to:


That's gotta be the most convoluted idea for a hack I've ever heard of.



Hehe- I'll take that as a compliment

In reply to:


So why such importance to free up the empeg serial port?


Well... I got this shiny new OBD-II reader that I'm trying to get to work under Linux using freediag. And when I do- then I'm going to hack up an interface for it to work in the Empeg.



Posted by: tfabris

Re: Ideas for a cheap GpsD device - 03/06/2004 14:45

Heh, it was meant as the highest compliment. I've been known to do convoluted hacks myself like that.

Of course, I'm a brute force guy myself, and would probably just rig up a serial A/B switch in the car so that I could switch between the two devices.
Posted by: siberia37

Re: Ideas for a cheap GpsD device - 03/06/2004 19:52

A serial A/B switch? Darn it Tony that's just too logical you ruined my fun. How is a guy supposed to be creative when you come up with logical cheap solutions like that? Only problem is I would have to get a lot of DB9->DB25 converters because I can't find a DB9 A/B switch.. o-well still cheaper than hacking a wireless router just not as much fun.
Posted by: Daria

Re: Ideas for a cheap GpsD device - 03/06/2004 20:55

This is an idea I hadn't considered. It still doesn't get me enough serial ports, I also want one for a ppp uplink.
Posted by: tfabris

Re: Ideas for a cheap GpsD device - 03/06/2004 21:24

Only problem is I would have to get a lot of DB9->DB25 converters because I can't find a DB9 A/B switch
 You'd leave it in one piece? Sheesh, I'd dismantle it completely and wire everything directly so that there was nothing but the rotary switch mounted neatly somewhere on the dash. Who needs actual plugs?
Posted by: jimhogan

Re: Ideas for a cheap GpsD device - 16/11/2004 02:59

Quote:
This is an idea I hadn't considered. It still doesn't get me enough serial ports, I also want one for a ppp uplink.

Why did you want all those serial ports? Curious.

And, hey! I see gpsd is all shiny and new like a spoon!
Posted by: Daria

Re: Ideas for a cheap GpsD device - 16/11/2004 03:28

One for a GPS. One for a ppp uplink. There was some third thing. (maybe one for future use)
Posted by: jimhogan

Re: Ideas for a cheap GpsD device - 30/11/2004 02:02

Quote:
One for a GPS. One for a ppp uplink. There was some third thing. (maybe one for future use)

Well, I just popped the lid on my V2 WRT54G last night and I found that Serial port mod page and I am ready to rock. If I can make them both DTE, I am figuring ttyS0 for GPS and ttyS1 for clock display (not sure on the details on that). Anyhow, a retail WRT54G is cheaper than any other Linux SBC I can find!

I see that some gent has posted an NTP source patch to allow NTP to read nmead via port-->device symlink. Has anyone looked at getting GPSD included in NTPD as an official driver?

Precise time is more and more important, after all.
Posted by: Daria

Re: Ideas for a cheap GpsD device - 30/11/2004 02:30

gpsd doesn't belong in ntpd. a gpsd client might, but really, does not. gpsd doesn't provide fine enough time resolution. it's a hack. yuck.
Posted by: jimhogan

Re: Ideas for a cheap GpsD device - 03/12/2004 00:30

Quote:
gpsd doesn't belong in ntpd. a gpsd client might, but really, does not. gpsd doesn't provide fine enough time resolution. it's a hack. yuck.

Well, I am increasingly interested in ntp and timing, but I am not a precision snob. Plus or minus a half second is fine by me, so I think ntp time derived from gpsd would be excellent.

Of interest, when I looked at the type 20 (non 1PPS) NMEA driver for ntp, I found that the patch that this guy wrote to take ntp time from nmead has been adopted in ntp driver source.

So I asked "Why wouldn't this work with gpsd?" And in fact it does. Symlinked loacalhost:2947 to /dev/gpsx and babing. See attached screenshot.

Only minor problem is that it stops reading and pauses at regular intervals, so NTP reachability stat never gets to where it should be. NTP pauses for about 25 seconds and then resumes after an incrementing auth_agekeys message. That may have something to do with my setup.

But it works more or less. It doesn't look like nmead is one of the projects you guys are going to assimilate/unfork, but maybe youse guys should talk!.
Posted by: Daria

Re: Ideas for a cheap GpsD device - 03/12/2004 02:17

Quote:
But it works more or less. It doesn't look like nmead is one of the projects you guys are going to assimilate/unfork, but maybe youse guys should talk!.


gpsd wasn't my project, I adopted it. nmead doesn't look like it does anything that makes it interesting. my rule is "don't write something new where existing tools suffice", which is why i picked up gpsd. could you imagine what software we might have if everyone and his brother hadn't written an mpeg video player (most of them based on the same libraries, just mostly "gui of the week")?
Posted by: jimhogan

Re: Ideas for a cheap GpsD device - 03/12/2004 02:47

Quote:
gpsd wasn't my project, I adopted it. nmead doesn't look like it does anything that makes it interesting. my rule is "don't write something new where existing tools suffice", which is why i picked up gpsd. could you imagine what software we might have if everyone and his brother hadn't written an mpeg video player (most of them based on the same libraries, just mostly "gui of the week")?

I heartily embrace your world-weary attitude with respect to everybody and their brother. I just found it interesting that that gent wrote an ntp patch for the less capable nmead (a patch that does something I like) that also happens to work with the more capable gpsd.

My goal is simple: have fewer than 2 GPS in my car!