Over two years in the making, I've finally started on my touchscreen interface project. Haven't really gotten very far, but I did manage to hook up an osciloscope to the touchscreens databus. According to the Helms, the data bus is differential. I hooked the scope's ground to the negative side, and the probe to the positive side (scope probe's ground is floating from earth ground).

I set the scope to auto trigger, and pressed the menu button (the physical button, not on the touchscreen).

These images are what came over the bus. The first image is the entire data exchange, the others are zoomed into various parts of the first.

I'm not quite sure what to make of this just yet. It doesn't look like any signalling that I am familiar with (I was hoping for RS485 or CAN). If anyone has any ideas, please share them.

Dave
dave@morecaffeine.net

 

Ummmm May I ask what exactly you are doing?

 

Well, my goal is to hook up a computer. Have the computer output video to the nav screen, and also be able to use the touchscreen to interact with the computer. I'm envisioning an mp3 player, dvd player, cell phone interface, OBD interface, really the possibilities are endless.

I just need to figure out how the screen up front talks to the nav box in the trunk.

 

oh hell ya that sounds great!, I have always wanted to be able to get my winamp on my screen or something like that. So you got my support

 

Save yourself oodles of time
work a little extra in teh time you would have spent in it
buy avelectronics box and hook computer up though it

 

but the avelectronics box will not alow him to control the computer via the touch screen... i believe that is his whole intention in doing it..

 

oh, sorry
well best of luck
keep us informed

 

Well, I haven't made much progress myself, however I did find an interesting thread on clubtsx:

http://www.clubtsx.com/bbs/showthread.php?t=2994

tsxer took some scope pictures, and they apear to be the same as what I've got....

 

Just thought I'd share the site that gave me the inspiration to start working on this project again....

This guy did a really nice job.... Check it out....

http://www.mujmac.cz/art/hw/tatra_mac_eng.html

 

I've found out a little bit more about GA-NET II. Someone was kind enought to point out to me that GA-NET II was really a protocol developed by NEC, IE Bus. Here is the chip that is used in the Nav Units:

http://www.necel.com/partic/function...s/d72042b.html

About 6 months ago myself and a friend of mine had hooked up a data recorder to the Data Bus on his car and recored a bunch of data. We were never able to make much sense of it untill it was pointed out that it was really IEBus. I wrote a quick program to churn through the recorded data and decode the data packets. A good portion of it seems to make sense to me now. I can tell what button or touchscreen location was pressed. Unfortunately I can't seem to get my hands on those NEC chips (they are sold by NEC automotive group in japan and I don't know where to order them from, I spoke to an NEC rep in the US but haven't had any luck so far).

I am probably going to try to design my own decoder chip in programmable logic one of these days when I have some more time.

Just wanted to share this since I haven't been able to find any information about GA-NET II on the web anywhere.

If anyone needs any more information or would like a copy of my data captures and decoder program feel free to email me at dave@morecaffeine.net

Dave

 

Austin519 on AW.com was hooking up a computer to his car. Not sure if it's as complex as your job, but you could always contact him for some pointers if he has any.