KillaItalian904

iTrader: (16)

I just got an inside peek in the tactrix cable. they put all the circuitry within the big OBD2 connector. My version would have to have a black box attached to the wire with circuit inside, until i can get a real silicon board pressed. so for all those people who were wondering if it was a simple wire to wire connection internally... its not.

djh

I knew you'd figure that out! For a little background, Evo OBD-II uses the ISO-9141 spec. It's a serial protocol but *NOT* electrically compatible with RS-232 (your basic PC serial port) or (by a long shot) USB.

If you really want to experiment try building "Jeff's" cable: http://www.planetfall.com/~jeff/obdii/ This is a very simple cable that uses opto-isolators and some discrete transistors to do the electrical translation. Don't be scared by the VW references.

Now this only provides the physical layer translation, all the OBD-II protocol has to be implemented in software, and there's a lot of tricky baud-rate changes and timing issues to consider. For some old, but still working linux software check out freediag: http://freediag.sourceforge.net/ Malibu Jack's (http://www.aktivematrix.com) Mitsulogger should work with this cable.

Roadman's cable, the one that lemmonhead posted, adds a custom-programmed microcontroller to handle the baud-rate and timing issues. The down-side is that this introduces its own protocol you have to program to, and you're limited to doing what the chip's been programmed to do. You can use Roadman's software or freediag.

Neither of the above will work with software meant for the tactrix cable -- they don't have a USB interface, and they can't be used for flashing. You aren't going to make a tactrix cable cheaper than you can buy it. It's not at all "so easy so cheap!"

Dave

jaxredevo1

iTrader: (1)

wow he knows whats hes talking about

mcwop23

iTrader: (7)

i just hope joe doesn't destroy my tactrix cable (j/k)

jaxredevo1

iTrader: (1)

i think it will be ok lol

lemmonhead

wrong, it will work, communication protocol works on many different physical layers. Serial is serial period.
anyways anyone with basic soldering skills and willing to do research on getting parts can make the cable way less than the $89.00 cable.
shoot im up to make cables for 50.00 bucks I guess if anyone wants them.

Evolessfornow

iTrader: (28)

You can count me in if you are making cables. As long as I can use 'em to tune with I'm set.

lemmonhead

well im not a vender, would i get in trouble doing this.
mods?

KillaItalian904

iTrader: (16)

i already ordered the parts just got some in last night. i will try it both ways... trhe cicuit that lemmonhead provided and the smaller circuit. As far as development goes, thats what i do and i work with several EE brainiacs that are willing to help with the programming... i think its feasible. You can use sofware to convert the data once you overcome the hurtles of making them electrically compatible. Once the data gets the serial on the laptop its fair game for the programmer. Snooping in on the raw data comming out of a tactrix cable may shed some light on the data input that ecuflash and evoscan etc are looking for from a tactrix cable. Even making a small utility in .net you could acheive the desired communications protocol

djh

You know the design for the Tactrix cable is available in the forums on openecu.org.

Lemmonhead doesn't know what he's talking about. ISO9141 and RS232 are not compatible. Roadman's cable has its own protocol and is not just a "level shifter." Definitely go for it if you want to DIY, but remember the grad student's motto: a week in the lab will save you an afternoon in the library. You now have a few places you can look for information from people who've been there, done that, and are happy to share. Just don't start connecting wires without understanding what you're doing.

One more really simple interface cable: http://prj.perquin.com/obdii/

Dave

lemmonhead

I think i know what im talking about being a controls engineer with a B.A degree in Electrical Engineering and having work experience in communication protocols.
I designed a "black box" multi protocol solution for Microscan Laser bar code which previously only worked for RS-232 to able to communicate via protocols profibus, MODBUS, USB, canbus,eithernet.
I also currently work in the Power industry where many different protocol communications are used.

lemmonhead

here read ecuflash
http://forums.openecu.org/viewtopic.php?t=138
read online encyclopedia on protocols.
http://en.wikipedia.org/wiki/ISO9141

80210

iTrader: (23)

Arlight this is great stuff. I bought the cable and had no problem spending the 75 to get it used. In all honesty, tuning for the evo is cheap for any used to have access to it. However,

THIS IS AN AWSOME THREAD!!

The point here might not even have to be cheaper or more expensive, it's acquiring the knowledge to learn how these work! Great stuff, even if it costs the same, please continue! I'm interested.

KillaItalian904

iTrader: (16)

got the parts today im begining assembly.... if only i could get evoscan to work with my real tactrix cable.... then i would be happy. I have a possible solution the output files that evoscan saves are just simple CSV. i could write a program in .net that converts the read data to the same csv style that evo scan uses and all the same data formatting. that way people could use evoscan to replay the logs created. it may not be able to log directly since this is not a tactrix cable... but it will at least be able to read the logs second hand.

EvoBroMA

you can probably make the cable for $50, but its no where near as easy as you make it sound. maybe you can solder some pieces together. you should do it and let us know how it goes.

I have a B.S. in engineering and also work in the power industry going on 10 years now. I know exactly what it takes to make the cable because colby has been posting the schematics of the different revisions.

also the money you pay for the cable doesn't just go to the cable - it goes to funding the development of the software.

edit: i really think people should try and make their own cables, that way they can figure out how these cables actually work. I do not like the PRJ design because it has no form of electrical isolation. use at your own risk.



also noteable in the tactrix design are electrical isolation (not using optoisolators for the current version of the cable.) and using an FTDI usb to serial converter IC. he uses the FTDI in bit bang mode during initialization.



here's a nice PCB layout of one of colby's designs. this is whats in the cable housing.


you can see a spot for the crystal (X1), and the fine pitch FTDI IC (U5).