Jan, the GPS software is great, and very useful. I'm quite impressed! I've been playing with it since last night.

It wouldn't be an empeg project without feature requests, though, so here's my pie-in-the-sky wish list.


- My GPS unit is notorious for taking a long time to lock onto satellites and start being useful. Often, it takes 5 minutes between the time I start the GPS application and the time that it's actually able to track my movement. So what I'm wondering is if, at player boot up time, when the GPS app is first called by preinit, it could at that time send the command to activate the GPS unit and start its initialization. So that way, later, when I finally do go into the GPS application, the sats will be there when I come into the menu. This could, of course, be optionally disabled for those whose GPS units are solely battery powered. By the same token, I would like to make sure that the unit stays on in the background even when I exit the GPS software. I think it has a timeout of 90 seconds where if you don't talk to it for that long, it will shut itself down. So I think your software has to actively be there doing something, however small, the whole time. Not sure how that works on these things, though. (Note: It seems to already do this, at least the part about keeping the GPS active after I exit the GPSapp. Does it? I exited the GPS software for a few minutes, then went back in, and the satellites were still there.)

- I would like to see the software always count down to the next turn on the map screen, with the actual text of the next turn up on the screen. Right now there is the option of a "popup", but I spent a lot of time last night staring at a map screen with no text, despite toggling the popup feature on and off. I would come up to turns and it didn't pop up and tell me the turn. I'd rather just have the current turn's text be on the screen 100 percent of the time.

- Better indication of toggle states. For instance, a lot of the menu items are toggles, but I have no idea if I'm toggling them on or off. Popups, for instance.

- It seems like the right-hand side of the map screen is a distance to the final destination, a direction to the final destination, and a distance to the next turn. (Not sure). I would much rather see it be (optionally), a distance to next turn (large), estimated TIME to next turn (smaller), and current speed/altitude. No arrow.

- In the all-text screen, I'd like to see the left and right buttons do something useful, like scroll through the list of turns in addition to the knob as it does know.

- I'd like to see the knob be able to be volume control for music player software even when still inside the GPS software. Is that possible?

- The short knob press should do something useful in the GPS software (doesn't seem to do anything at the moment). Perhaps it could be used to toggle between player track/volume controls and the GPS software controls. That way you could at least switch tracks and adjust the volume without exiting the GPS software.

- When you hold down the bottom button, it does not offer immediate feedback when switching screens. You have to release the held button to make the screen switch. This is opposite of how the other button hold features work on the player, which will switch the screen or feature as soon as the button was held long enough to activate that feature. Although both behaviors have a certain user interface validity, I think the GPS software should be consistent with the rest of the player in this regard.

- I'd like to have the ability to set default program startup options such as rubber band off, coordinates off, etc. That way, I don't have to set them every time I start the GPS app. It's OK if these have to go into config.ini or some other place, no need to use flash RAM for this.

- Corrolary: I'd like the ability to remove menu items completely. For instance, if I always like the rubberband off, the coordinates off, and always want it to be miles instead of clicks, then I would like to remove those selections from the menu so I don't have to scroll through them when I'm in the menu.

- Bugfix needed: Blinky satellite data screen as illustrated in the animated GIF file in my other thread.

- Bugfix needed: Sometimes keystrokes in the GPS app get through to the player software. Case in point: More than once, pressing the right button on the faceplate began to fast forward the current song and it did not stop fast forwarding until I exited the software back to the player and pressed the button again. Not sure how to force this to happen, it's intermittent. Seems to happen more easily if you are in the GPS software, then you exit the GPS software, then you go back into it. I got it to happen just now by doing that.

- The menu selection box looks the same as the "No Satellite Data" box and is in the same place on the screen. So it looks strange atop the "No Satellite Data" box. Perhaps the menu should be up higher on the screen and/or a different style than center-screen message box. Or vice versa.

- The message "Waiting for GPS Location". Should it be something like "Waiting for data from GPS receiver" instead? And the "No Satellite Data" message, perhaps it should be "Receiver found, looking for satellites" or something like that. This would have prevented my initial installation confusion, not knowing whether the GPS unit and serial cable were working or not.

- Can the actual NMEA sentences be scrolled in a small window on the satellite data screen? I saw a Palm app which did this, and it was very useful in determining that the GPS unit was working even before it got a satellite lock.

it could at that time send the command to activate the GPS unit and start its initialization.

That command is called "opening the serial port".

but I spent a lot of time last night staring at a map screen with no text, despite toggling the popup feature on and

It appears that the software can become confused and not realize you're coming up on a turn. It was estimating 230 miles to next waypoint on a 139 mile trip I made.

That way you could at least switch tracks and adjust the volume without exiting the GPS software.

You should get a remote for your empeg

I'll be selfish and say that autorouting is more interesting to me than practically any of your wishlist items.

Maybe I should take my laptop and try to work on some of this stuff for the hour I'll be on the train Friday morning.

You should get a remote for your empeg

If this is true, if the remote works on the music while the GPS software is running, then I withdraw that request. Pile more functions onto the front panel buttons instead.

f this is true, if the remote works on the music while the GPS software is running, then I withdraw that request.

Try it. It works for me.

If your GPS doesn't begin the aquisition process immediately upon the application of power then perhaps it is time to take advantage of one of the "fire sale" receivers now available for $15-$25. The one I have is up and running by the time the Empeg has booted and I can select GPSapp.

My remote seems to work just fine while GPSapp is running.

If you were to scan through some of the threads below I think you would find a lot of answers to these and other questions you are asking. They may not be in the FAQ (yet) but the discussion and problem solving that is going on here is responsive, productive and quite inclusive.

http://empeg.comms.net/php/showflat.php?Cat=&Board=hackers_prog&Number=119138&page=0&view=collapsed&sb=5&o=0&fpart=

http://empeg.comms.net/php/showflat.php?Cat=&Board=hackers_prog&Number=115801&page=0&view=collapsed&sb=5&o=0&fpart=

http://empeg.comms.net/php/showflat.php?Cat=&Board=hackers_prog&Number=104935&page=0&view=collapsed&sb=5&o=0&fpart=

You do illustrate a good point in that each of us does have out own set of preferences about how we like to interact with an application and with the geography. Any application will benefit from a certain degree of configurability. On the other hand, Jan has just recently started on this project and he has made more progress per unit time than anyone would or could ever expect, so I think we should all be grateful for what he has done along with his willingness to listen to all of our suggestions

Lynn

Jan has just recently started on this project and he has made more progress per unit time than anyone would or could ever expect, so I think we should all be grateful for what he has done along with his willingness to listen to all of our suggestions

Absolutely agreed. I think it's great, and that's just my "wish list", key word being "wish".

My GPS unit is notorious for taking a long time to lock onto satellites and start being useful. Often, it takes 5 minutes between the time I start the GPS application and the time that it's actually able to track my movement.

FYI, the 5 minute time is about right for a GPS that dosen't store any data on where it is, or dosen't have an RTC. My Garmin would have taken about that long to find it's location when I went to the Ohio empeg meet. Lucially, the Garmin stores the last location, and has a feature that you can select your rough location, and it will speed up the satelite discovery phase. Huge distance/elevation changes throw it off.

I guess it's time for me to tear my dash apart so I can participate in all the GPS fun. It's why I bought my cheepo GPS antenna ages ago, and it's still stuck in the front windshield from it's last usage with my laptop this past May.

I like this kind of feedback. A lot of these suggestions make a lot of sense. I can't really do much about the GPS lock time, as ellweber said it probably already starts searching as soon as the empeg is turned on (i.e. when the remote amp wire becomes active). The NMEA protocol is totally one-sided, and as there are no DTR or RTS/CTS signals and I never send anything, the GPS really doesn't know whether gpsapp is active or not. The long time before a lock probably is as Drakino suggested, the receiver doesn't remember satellite trajectories, last known fix and the time while it is powered down. One solution is to always keep it powered, don't know how quickly it could drain a car battery though. The other solution is probably similar to what the earthmate and tripmate drivers in gpsd are doing, find the magic sequence to upload the current time and approximate location to the gps. Time can come from the empeg clock, while the position can be stored in a config.ini file, even if it is off by about 100 miles it doesn't really matter much, and when it is off by more it will just take 5 minutes again. However, I have no clue as to what the magic incantations might be.

Menu toggle indicators, yeah the menus were just a quick hack. I guess I had 'make the menus better' in the todo-list since the first release. They probably should also be 'context sensitive', toggling 'tracklog' doesn't do anything in the satellite screen, and clearly those popups need some more work. Keeping them up permanently probably isn't that difficult, but others would like to not even see them at all. So with a better menu structure it could become off/popup/on.

Right hand side is distance to final destination, direction to the next waypoint and distance to the next waypoint. There is a distance/time menu option that changes this to ETE (estimated time elapsed) to final destination, direction and ETE to next waypoint. I don't know why everyone wants altitude, maybe I should get a better car that also drives vertically like everyone elses. Speed is probably a nice addition, but do we want an averaged 'velocity made good', i.e. velocity towards the target, or the actual GPS reported speed. I already have both numbers, just need to add them.

And why don't you like the arrow? I find it useful when I don't have an actual route, but just a destination point. As soon as the arrow points sideways I know I probably have to take the next available turn.

The remote IR codes are not intercepted, and it wouldn't be a problem to not hijack the knob turns, but to keep the knob press. Ofcourse we do need some space on the screen to visualize that the knob works for volume (I have a headunit and never use the knob on the empeg for volume control).

I should already have that blinky satellite screen fixed, just need to test it.

That ghosting of the buttons should not happen except if hijack is forgetting to 'hijack' the button codes. My kernel patch was basically prompted by the fact that people had their player switch to AUX and back, which in turn could very well result from the knob press ghosting through.
This is a clear indication that there is something more insidious going on than I first suspected.

The menu and the 'no satellite data' actually use exactly the same 'draw_msg' function to put themselves on the screen, so yeah they probably look quite similar

It would be hard to scroll the actual NMEA messages because by the time I update the screen, I'm working with something more like a summary of the data I got from parsing the messages.

osen't have an RTC

IIRC you can cheat with the Rand McNally unit since it's a Zodiac, by sending the NMEA sentence $PRWIINIT,V,,,,,,,,,,,,hhmmss,ddmmyy,
to init the clock.

Zodiac doc attached.

My wish list is just a simple FAQ for someone who's never done anything with GPS. Which GPS receivers work with the program, how to connect them to the Empeg (preferably solder-free.) I can figure out all the software crap, but I don't know all the ins and outs of GPS products. Are there ones that can pretty much just plug into the serial port and work?

Actually the time delay is probably from the moment that the empeg provides power to the RA line, and not when the serial port is opened. GPS units use an almanac and their known location to know which satellites should be visible, and if they don't have either, they have to wait until they hear an almanac broadcast from one of the satellites - this could easily take 15-20 minutes. Some receivers allow for an almanac to be loaded into them via software which would prevent this delay, although battery backup should prevent the almanac from being lost once acquired. It is possible that one of the other pins on the 'serial' port is actually a 3-5V memory line, but YMMV.

Hmmm... no posts for an hour, and then 4 in 3 minutes....I guess that I'm not the only one who watched Westwing.

I can't really do much about the GPS lock time, as ellweber said it probably already starts searching as soon as the empeg is turned on (i.e. when the remote amp wire becomes active).

Actually I guess I don't know about these but the Earthmate only turns itself on when the serial port is opened.

find the magic sequence to upload the current time and approximate location to the gps

I just sent it. I can contribute a patch, but it wants time in UTC. Do we want to rely on people having the right time? If so, tell me and I'll get a patch out tonight

I never got ETE working for me, but then, it might have been when gpsapp (0.7) was confused about the location of the next waypoint as relative to my position. (I was closing on it, but the estimated distance was increasing... but was almost 2x the distance of the whole trip, so I don't think it just "missed" me passing one.)

It would be hard to scroll the actual NMEA messages because by the time I update the screen, I'm working with something more like a summary of the data I got from parsing the messages.

How about an icon indicating data being received?

Which GPS receivers work with the program

Any receiver which speaks NMEA and supports serial output should "just work". I know of these exceptions:
-Earthmate doesn't speak NMEA
-Tripmate does but wants to hear the string "$IIGPQ,ASTRAL*73" before it starts talking; It makes life easy by saying ASTRAL to you until you answer.

I guess that I'm not the only one who watched Westwing.

I was eating.

Attachment isn't found on the server, can I grab it out of AFS somewhere?

Does the empeg tick it's clock in local time or UNIX time? I guess that if we want to send some initial coordinates they would probably come out of config.ini, so we could store a timezone offset in there as well.

ETE is continually changing. Initially I just did total distance / gps speed, which wasn't working too well, so then I tried averaged speed, then velocity made good towards the closest point in the route, still no good. Now it is averaged velocity made good towards the next waypoint, which seems to be giving the best estimate up until now.

That tripmate initialization sounds like a trivial addition to the NMEA parser.

/afs/andrew.cmu.edu/usr/shadow/Zodiac.pdf

I wonder why it didn't attach?

The tripmate init string is trivial. The Rockwell time init probably is too because you can send it safely regardless of what you have.

I guess I'll attach my empeg to the network and check the RTC.

As far as ETE, it wasn't changing, I was getting I think --:--

Hmm, it should only give --?-- when it doesn't have a speed estimate. I probably got something wrong somewhere. Was this using NMEA?

Mine looks to be set to UTC (the real time clock that is)

Yup. I only have one SVee6 set up, and it's NMEA. Likewise my Magellan.

Here's a cheap binary to print the date, since there's no /bin/date

Edit: and here's the source
#include <stdio.h>
#include <sys/types.h>

#include <time.h>

main() {
time_t when;
struct tm *tm;
time (&when);
tm = gmtime(&when);
printf("%02d/%02d/%04d %02d:%02d:%02d UTC\n", tm->tm_mday, tm->tm_mon+1, tm->tm_year+1900, tm->tm_hour, tm->tm_min, tm->tm_sec);
}

it probably already starts searching as soon as the empeg is turned on (i.e. when the remote amp wire becomes active).

In my case, I don't think that's what's happening. The one I've got doesn't have an off or on per se. It has a Li-Ion battery so in theory, it could be on all the time and just be getting charged up whenever I'm supplying it with power. But the instructions for the palm software say something about it shutting down automatically after 90 seconds of inactivity, and that the software can command it to stay on for longer than that. Or something like that, I don't understand it. Perhaps it's got a sensing switch on the power jack and goes into "always on" mode when the jack is plugged in? If that's the case then strange things should happen if I leave it plugged in all the time as it is now. The dox are really sketchy on the subject, I don't know how it's handled. But I got the impression that all on/off commands were "soft" and delivered through the serial port.

I was just assuming that it wasn't powering up until after I launched the GPS app the first time. I could be wrong.

Right hand side is distance to final destination, direction to the next waypoint and distance to the next waypoint. There is a distance/time menu option that changes this to ETE (estimated time elapsed) to final destination, direction and ETE to next waypoint.

Right. What I'm saying is that I couldn't care less about final destination distance or time. All I want is a countdown to the next waypoint, in both time and distance.

And why don't you like the arrow?

It's a very nice arrow (pats on head). I don't need it because I've already got the rubberband option (indicates the same thing) and the screen real estate would be better served with more fun stuff like speed, altitude, or more room for the popup text. If everyone else likes the arrow, that's fine. Make it an option.

It would be hard to scroll the actual NMEA messages because by the time I update the screen, I'm working with something more like a summary of the data I got from parsing the messages.

Ah well, no big deal, it would kinda be just eye candy. And only useful for receivers like mine where you sit there and wonder if it's even working at all.

I don't understand how GPS receivers work, and I'm curious: What's the difference between a gray hollow bar and a solid white bar on the satellite screen?

Ofcourse we do need some space on the screen to visualize that the knob works for volume

Now that I know you can use the remote to control the player app, I've changed my mind and would rather see the knob do what it currently does which is scroll through the list of waypoints. Works well for that.

I don't understand how GPS receivers work, and I'm curious

Read the GPS Guide. It explains the entire system in pretty decent detail, but is easy to understand,

Considering that gpsapp is only passively listening to the serial port in NMEA mode. Your receiver must be always on as long as it receives power through the jack.

I had the same 'I wonder if it really works' feeling when I connected the SV6. And it is one of the reasons why I added the signal strength display in the first place. Most things I write is to 'scratch an itch', if it bugs me enough I fix it.

The difference between hollow/dim and solid/bright right now is that the solid bars are the satellites used for the location fix, the others are either to weak or intermittend or just have an unlucky position in the sky so they can't add anything to the triangulation or something.

However, things keep changing and ITNR the bright vs. dim color will indicate whether we received a measument for that satellite within the last 2 seconds. I.e. you could have bright/hollow bars for satellites that are still received promptly but probably are not in the solution because they are too close to the horizon, or too weak. And dim/hollow bars for satellites that are currently obscured, and possibly even dim/solid bars for satellites that were used for the last solution, but are currently obscured (when we drive into a tunnel?)

And it doesn't switch from the "Waiting for GPS location" screen to the "No Satellite Data" screen until it hears something valid from the GPS?

Very interesting document, Tom, thanks.

Well, until it gets any input. It is basically waiting for the first screen refresh. So a button press would get it to the no satellite data message as well. But as long as you don't touch the empeg buttons only the serial data should cause a screen update.

Okay, so can someone recommend a good GPS receiver then? I'm imagining just installing GPSapp, plugging a GPS receiver into my car's DC power socket, plugging in the Empeg's serial cable, and having everything Just Plain Work (tm). Are we there yet?

I'm imagining just installing GPSapp, plugging a GPS receiver into my car's DC power socket, plugging in the Empeg's serial cable, and having everything Just Plain Work (tm). Are we there yet?

Yes, that's essentially what I did.

Important to remember, though, that the serial cable needs to be three wires only: Gnd, Rx, and Tx. Because the in-car serial port has some screwy stuff going on with certain pins. And also there will be some trial-and-error involved in the correct "swap" of Rx and Tx.

And, of course, installing preinit and gpsapp was tricky because of the difficulty I had creating the /programs0 partition. But maybe by the time you get the GPS receiver, Preinint will have been updated to automatically create /programs0 for you. Just remember, don't have the WinZip smart CR/LF conversion on when you extract the preinit TAR file.

And, of course, installing preinit and gpsapp was tricky because of the difficulty I had creating the /programs0 partition. But maybe by the time you get the GPS receiver, Preinint will have been updated to automatically create /programs0 for you. Just remember, don't have the WinZip smart CR/LF conversion on when you extract the preinit TAR file.

Thbpbpbpt. Winzip? I'm a UNIX guy, remember?

I will have no problem getting preinit and gpsapp working properly. The software stuff is the least of my concern. I just saw that you had to solder all sorts of things... I wanted a painless install but I guess I'll be hacking up a DB-9 cable anyway. Any kind of schematic you can provide? Even if it's just one of those fixed-width courier text diagrams on the BBS. Are all GPS receivers going to have the same pin allignment and so forth?

I just saw that you had to solder all sorts of things

Not all sorts of things, just pins 2, 3, and 5 of a serial cable.

And if it were a regular GPS unit with a regular serial port, I wouldn't even have had to do that. The only reason I had to solder was because my GPS didn't come with a serial port, it came with a Palm3 connector. So I had to solder onto the three pins on its PCB that corresponded with the three pins of the serial data on the Palm3 connector.

It's possible that a straight-through serial cable would just work for you. But if you run into trouble, just open the hood of the serial cable and pull all pins except 2/3/5 and try swaps of 2/3 until it works. (2/3=rx/tx, 5=gnd).

Sled serial is DCE, but also has 12V (Remote Amp) on pin4, and a couple of the handshake lines are actually Dimmer and Mute, but I forget which.

I would bet that most GPS receivers are also DCE, so you would need to cross TxD and RxD in the cable.

Basically, you need (assuming GPS is standard DCE)

Sled<->GPS
2 <--> 3
3 <--> 2
5 <--> 5 (Ground)
4 <--> GPS 12V in. (Assuming your GPS accepts 12V in - otherwise a power regulator will be req'd)

but also has 12V (Remote Amp) on pin4

DAMN, I'd forgotten that. I went to a lot of trouble to wire up to the remote amp line on the main wiring harness. I could have saved myself some work if I'd just thought about it.

Any good affordable GPS's accept 12V in on pin 4? I'd like the easiest (plug-and-play) solution available...

Probably NONE, pin 4 is DTR. So you're going to have to at least pull some pins.

Easiest solution is probably a garmin etrex venture ($150-200?) which comes packaged with a pc interface cable (db9 serial) and a gender changer ($2-5?) to connect it to the sled's serial cable. It eats a pair of AA's in about 10-20 hours though. But then again, as it doesn't rely on the car for a power supply, you can use it for geocaching without needing a 4x4. Nothing will expect 12V on pin 4, that's an empeg specific feature.

Ah.

Hm...

I don't like the idea of relying on batteries. I wouldn't care much about geocaching.

The ideal GPS receiver for me would *support* battery power, but also have some easy way for me to give it power from the Empeg's serial connector. I don't mind cutting some wire and soldering a little bit to do it, but I don't want to have to open a brand new GPS receiver up to do it.

but I don't want to have to open a brand new GPS receiver up to do it.

For me, it was the $9.50 price tag and the fact that all of the Palm software sucked that gave me the confidence to do it.

Garmin sells these combination 12v cigarette adapter/serial cables on their website. They are pretty expensive. Some people are building their own and are often selling them on ebay.

But it all depends on what you want to do. Expensive gps's have builtin maps and as such can be really usable by themselves. But there are also things like the Earthmate, and gps-mouses, and things like the SV6 or Oncore receivers, that have no display and completely rely on a laptop, pda, or empeg , to handle the user interface, and in some cases need a custom built 12V->5V power supply or RS232 line level convertor. Tony got lucky there, nothing to solder but 3 wires.

Yeah, I don't necessarily need it to have its own screen, as I mainly want it as an in-car thing that works with the Empeg. I'd rather take advantage of the Emeg's VFD... Even if it is limited in what it can display clearly, it's good enough for my purposes.

I'll look up those SV6 and Oncore ones you mentioned... I assume they both speak NMEA and would be happy talking to your GPSApp? I'll probably pick the one that will be easiest to hack to work off the 12V power on the Empeg's DB-9 cable. Not sure which that'd be, though.

Edit: Okay it seems the Oncore is just a board that I'd have to solder a DB-9 to... Probably not ideal for me. Couldn't find anything concrete on the Trimble SV6.

I did find this "GPS mouse." But it expects power from a PS/2 connection. Would I need something special to connect that to the 12V on pin 4 of the Empeg's DB-9? It says it supports the following NMEA messages: NMEA-0183 ver2.01 or Rockwell Binary, PRWIBIT, PRWILOG, PRWINIT, PRWIPRO, xxGPQ, GGA, GSA, GSV, RMC, VTG PRWIRID, PRWIBIT, PRWIZCH sentences. Is that good enough?

Low Power Consumption- 55mA/12V
On-board Power Supply- 4.5 to 16V
Looks perfect, you can hook it's power line (whatever goes to the ps2 port) directly to pin4.
Currenly I'm using GGA, GSA, GSV and from the other sentences it looks like it is the rockwell Zodiac chipset that dbrashear sent me the documentation for. It is probably identical to the chipset in the Palm III streetfindere, maybe even the same thing in different packaging.

Damn, 'cept they want $250 for that sucker. There's a cheap knockoff on EBay, but they don't say what kind of juice it needs. I'm guessing converting 12V to 5V isn't elementary.

It is with a $10 PT5101

        PT5101

         | | |

12V o----+ | +----+-------o 5V

           |      |

           |     === 100 uF capacitor

           |      |

GND o------+------+-------o GND

Here is a source for GPS at "fair" prices.

http://www.navtechgps.com/supply/equipment.asp?Line=smartant

The Garmin GPS 16 will do what you want and is somewhat less than $250.

You can also find antennas here but their stuff is new.

I have no connection but I delt with them in a previous life and I think they are legit.

Lynn

Hmm, I think this might be the animal I'm looking for...

If you get the one with the unterminated power/data cable, you could wire that to your own serial plug with pin4 as power and you'd literally have a single-plug solution. Nifty.

If the GPSapp software proves useful to me in the long run, I might have to save up for something like this just to get the fast aquisition times.

They don't seem to clarify the difference between the high voltage and low voltage models, though.

Of course, something like this is cheaper. Dunno if it uses a serial port or what, though.

From http://www.garmin.com/products/gps35/

GPS35-LVS Attached 10 foot power/data cable with bare wire ends. Accepts power from
unregulated low voltage power supplies between 3.6 and 6 VDC. Asynchronous serial data interfaces
via 2 serial ports with true RS-232 voltage level outputs.*

GPS35-HVS Attached 5 meter power/data cable with bare wire ends. Accepts power from
unregulated high voltage power supplies between 6 and 40 VDC. Asynchronous serial data interfaces
via 2 serial ports with true RS-232 voltage level outputs.*

GPS35PC Attached 10 foot power/data cable with female DB-9 serial connection, ready to attach to
your PC. Additional 8 foot power cable extension from the DB-9 connector terminates in a cigarette
lighter plug for easy application of power supply voltage between 6 and 40 VDC. Asynchronous serial
data interface via a single serial port with true RS-232 voltage level output.* **

*All serial inputs on all versions are compatible with either true RS-232 or TTL/CMOS voltage levels.
Port 1 uses NMEA 0183 data format. Port 2 transmits binary position and raw measurement data and
receives RTCM SC-104 differential corrections data, message types 1, 2, 3, and 9.



So the "low voltage" and "high voltage" numbers are clarified there, and the 35PC version just has the car adaptor plug instead of an unterminated wire. And just one serial port outputting NMEA, instead of one with NMEA and a 2nd one outputting binary data. Who cares?!?

So I guess the one I want is the high voltage one without the car adaptor. Since the 12V coming from the Empeg is within the 6V-40V range, it sounds like it's a no brainer.

Based on this page it is RS-232 but it wants 5V power from a laptop's keyboard port. It mentions a cigarette lighter adaptor, but I'm not sure if a software/hardware bundle from 2000 is going to have widely available accessories...

>can someone recommend a good GPS receiver then?

Avoid the Garmin eTrex series -- their dinky antennas render them near useless under tree cover, rainy skies, and even in my living room.

I got a Magellin "Meridian Platinum" (same as "Gold", plus compass, barometer, and temperature sensor.. only the compass is useful, though), which has a proper internal antenna that is mostly unaffected by trees, rain, single story dwellings, etc.. Other models from other brands also have good antennas.

Cheers

It is with a $10 PT5101

How much heat does it dissipate? I'm dissatisfied with the 7805 solution I have now, though truthfully I shouldn't worry since I bought some DC-DC converters salvaged from (I don't remember what, I think telco equipment) to put in both vehicles... useful since at least one is getting an access point as soon as I have a minute.

Next to nothing, it is a switching regulator probably has about 80% efficiency. As the gps draws about 1.2W (240ma at 5V), it is probably in the order of 0.3W. I mounted it inside the same aluminum box as the receiver, and the box gets warmer on the gps side than on the max233/pt5101 side.
It doesn't need an additional heatsink even when you draw a full amp at 5V.

Ok. Well, I guess if I build any more of these other than for vehicles which will get DC-DC converters the 7805s go out the window.

Only trouble is the PT5101 is £15 in the UK - little bit more than < £1 for a 7805. I bought a bag of 2A ones (in the oval cases) from a car boot sale for a couple of quid a few years back, so I'm going to use them otherwise fitting two cars with antennas and power circuits will cost more than the encore GPS units!

In fact, I have just paid $50 for two active antennas off ebay (inc shipping) - they qre quite nice and come with 16ft cables so I am pretty pleased. A fair amount of searching found £30 each was the cheapest I could find in the UK. I could have done better but at $50 I gave up wasting my time!

Gareth

I bought an Sv6 from bgmicro for $25, purely for the antenna to use with my Oncore. Then I found that antenna had a 6" cable, and no extension cable. With different connectors to the Oncore. Then I found out that the minimum quantitiy of RG174 that I could easily buy was 30ft which cost me about $30.

So $50 with shipping for 2 active antennas with 16ft cables doesn't sound too bad at all.


If anyone in the USA/Canada needs some RG174, but doesn't want to fork out for 30ft, I'm willing to sell some at $1.10 per foot (inc shipping). You'd have to deal with the connectors yourself - it'd just be a coil of wire.

anybody know if the empeg has a 5V line we can tap? Of course doing so would probably void your warranty immediately, but hooking up a home-built circuit shaddily soldered (in my case because my soldering skills are bad) to the serial port might too...

Two reasons for sticking with the 7805 approach. The first is that the 7805 is virtually free compared to any of the intergrated switchers and much easier to find as well. It isn't nearly as elegant or satisfying technically but who is going to see it? An extra watt in a car is easily provided and easily dissapated. I don't think any part of my 7805/SV6 is over 45 degrees C.

The other reason is that you are dealing with a radio receiver designed to recover a signal that is nominally -130 dbm at the antenna. We are talking about something that is well below the ambient noise level. GPS only works because of the spread spectrum, synchronous detection architecture. It doesn't take much noise to start to degrade the sensitivity of your preamp and switchers are clearly much noisier than three terminal series pass regulators.

If you do go the switcher route be careful with grounds and shielding. If you keep the radiated noise of the switcher and its external components (particularly the inductors and any schottky diodes) bottled up you can certainly make it work.

Lynn

Hmm, I have the switcher in the same aluminum box as the receiver's PCB. So although it probably is shielded well enough to avoid the antenna picking up any interference, it might still influence the receiver? At least now I see why I had a hard time getting a lock when everything was still a bunch of wired up parts on my desk.

Most of the receiver's RF stage is already shielded on the pcb - the only part that isn't is the (very short) pcb trace from the antenna connector to the RF circuitry within the shield. The antenna cable is also shielded. I would imagine that unless you got unlucky, the signal from an active antenna would swamp any noise that the trace could pick up from a PT5101.

yea, what he said.....