OnStar GPS Interface

Harry5150 · 01-10-2004, 12:25 PM

I don't think this has been already posted but...

If you have a GM vehicle with OnStar, apparently you can hook up a computer to the GPS antenna. I have a Ford so this doesn't really help me but I digress.

Free = Good

http://members.cox.net/onstar/

Here's a sample:

Quote:

The OnStar System is becoming more and more common as GM installs it by default in many of their vehicles. At the heart of this system is a GPS receiver, manufactured by Motorola, called the Oncore. Once you make a serial connection to this Oncore GPS, you can recieve real-time positioning information on your Laptop or PDA - In either Motorola's proprietary (but well documented) format, or in standard NMEA format.

In order to do this, you will need the following items:

A vehicle with OnStar
RS232-to-TTL Serial Level Converter
Torx T-10 (star shaped) screwdriver/bit
Solder Iron/Solder
Screwdriver/Wire Stripper/Pliers, etc.
After tearing apart my OnStar, I found the actual GPS board inside to be a Motorola Oncore GTPlus. I decided that the easiest way to interface with this would be to connect directly to this board, rather than trying to use the OnStar wiring. The main reason I decided to go this route was due to the lack of infomation about Onstar's wiring and protocols, and the wealth of information about the Motorola Oncore pin-outs and protocol. I also wanted to be able to talk directly to the GPS regardless of the current status of the OnStar system, and have no idea if that is possible through the OnStar's wiring.

In order to connect a serial port directly to the Oncore you will need an RS232 to TTL level converter. These are available for sale on the web, as well as schematics to build your own. I decided to use a pre-built converter, the RLC1 from Digital Nemesis. I chose this one because it was built into the DB9 shell, so it would require minimal wiring. I figured this was also one less thing for me to screw up. I cut the Molex connector off the end so I could solder it directly to the board, and soldered the RTS (Request to Send) and CTS (Clear to Send) wires together since these aren't used by the oncore.

Hcomplyr · 01-14-2004, 08:44 AM

*BUMP* i just found this on clubGP anyone with onstar should try it, too bad my car off by one year to get it

openminds · 05-15-2004, 01:11 PM

Here is another guide I did quite some time ago.
Hack into On$tar for your Chevy Avalanche

Some will say it is not worth the time to do it, buying a "puck" is easier. But what the heck, it's there, it's free, and you get some kind of satisfaction out of it.

Hcomplyr · 05-15-2004, 01:47 PM

well even you said reception is stronger, and you don't have to wait for the reconfiguration. i'd opt for the onstar mod if i had it

rgardjr · 05-15-2004, 08:08 PM

I was hoping to do this, but my 2003 Sierra doesn't have an easy way to tap into the Onstar GPS. Anyone who is going to buy the cable from Australia let me know and Iill make you a deal on mine-which I couldn't use.

Leddy · 05-15-2004, 08:18 PM

Check sig

Pictures http://www.cardomain.com/memberpage/238992/3

I went with this because my earthmate sucked. It was an older serial unit but still sucked. Onstar sucks even more. But there's that nice little GPS chip in there with an external antenna. Makes complete sense to me. I think the ttl was 10 bucks and wallah

openminds · 05-16-2004, 03:15 PM

Quote: Originally Posted by Hcomplyr

well even you said reception is stronger, and you don't have to wait for the reconfiguration. i'd opt for the onstar mod if i had it

YES, that is a major +. Acquisition time is negligible, as opposed to my Magellan Handheld. (Which can take up to 3 minutes or so sometimes.

openminds · 05-16-2004, 03:17 PM

Quote: Originally Posted by rgardjr

I was hoping to do this, but my 2003 Sierra doesn't have an easy way to tap into the Onstar GPS. Anyone who is going to buy the cable from Australia let me know and Iill make you a deal on mine-which I couldn't use.

Why couldn't you accomplish it with the 03 Sierra? Does it have a Sony board? If so, the pinouts are the same. Just need to track down either the Sony Software to configure it, or a Mapping Software that will read the Sony Binary output.

Firend did get it up on the Sony board, we are now trying to figure out the later. (Software, etc.)

rgardjr · 05-17-2004, 12:42 PM

Quote: Originally Posted by openminds

Why couldn't you accomplish it with the 03 Sierra? Does it have a Sony board? If so, the pinouts are the same. Just need to track down either the Sony Software to configure it, or a Mapping Software that will read the Sony Binary output.

Firend did get it up on the Sony board, we are now trying to figure out the later. (Software, etc.)

From what I've read they've changed the Onstar module considerably and the GPS module is now incorporated into the main board. There was a guy that tried to do it on an '03 Silverado and couldn't find any of the points to tap into. I tried to find the thread over at this forum http://www.aimoo.com/forum/freeboard.cfm?id=421724
but I couldn't find it any longer. His name is Wayne Dohnal and he did a very extensive job of trying to get it to work, but threw in the towel in the end. Here's a little bit of explanation from another thread I did find:
From the pictures this board is the same or very close to the cell phone board from my 2003 Sierra's OnStar box. Just for comparison, the label on my box carries the Motorola logo, "Assy Part No: 15184769", and "Base Part No: 15184770". I believe that the GPS receiver is a custom chip integrated onto the mainboard. I spent several hours searching for a serial data stream and I found two of them, but they are not the fixed bit-rate serial data that we would need. It looks more like a 2-wire signal to me, perhaps I2C or something similar. After a couple of days of getting nowhere I decided that we have been screwed by GM with a new, untappable design. I wish that somebody from GM or Motorola could post some real inside information here for us.
I finally bought an Oncore receiver off of eBay and put it in a small metal box along with the connectors, a backup battery, and voltage regulator. The GPS antenna on the truck works fine with it, but finding one of the mating MCX connectors was another royal pain.

openminds · 05-20-2004, 04:47 PM

Well, you definetly found the right alternative....

We did accomplish this mod in an 03 Chevy Avalanche. This truck had the same system as in my 02. I think GM just throws in what they have on the shelf at the time.

rgardjr · 05-20-2004, 06:02 PM

Quote: Originally Posted by openminds

Well, you definetly found the right alternative....

We did accomplish this mod in an 03 Chevy Avalanche. This truck had the same system as in my 02. I think GM just throws in what they have on the shelf at the time.

Actually, I didn't buy the other Onstar receiver off Ebay it was Wayne Dohal. I didn't do a very good job of quoting him. I just ended up using an Earthmate with a serial cable. If I ever tear into the dash again I'll take a look at the Onstar unit to see if it is the newer design.

aleromaster · 05-22-2004, 11:52 PM

GM is changing the onstar units to a digital ready unit instead of analog only as the older ones where.

sose · 05-27-2004, 04:50 PM

Hey openminds, do you have some info available on the Sony GPS chip???

I did so much to get my Avalanche ready for this mod, only to be crushed by having the damn sony chip..

Viscouse · 08-10-2005, 09:07 AM

Thought I'd drag this to the top.
First: props to openminds for coming up with this. This is an awesome idea.
Second: props to all the folks helping with my particluar challange over at Saabcentral.com.
Together, we're going to get this working in a 2003 Saab 9-3.

Anyway, what we've determined so far is that there is a Sony chip in there. Specifically a GXB3000 using a CXD2932 chip.
The pinouts are way different than what you have, but that is to be expected. My biggest hurdle is that I cannot find ANY info on the GXB3000 ANYWHERE. There is loads on the GXB2000 ( http://products.sel.sony.com/semi/PDF/GXB2000.pdf ), and they are similar. I can only hope the pinouts are the same.

Does anyone know where to find a spec sheet for the GXB3000?

Anyway, I have a 10 pin connector (all in 1 row), and have to determine which is pin 1. After that, and I scrape some dough for the RS232-to-TTL Serial Level Converter, I'll be in business.