OBDII to RS232 converter tech question.
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Melting Slicks
Joined: May 2000
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From: CenTex Texas
OBDII to RS232 converter tech question.
If OBDII is an ASM Standard and RS232 is an IEEE Standard then why is there a different converter box for GM/FORD/DC? What's inside the converter boxes that make them so special?
Also can someone who's fairly knowledgable in electronics build one from scratch, if given the necesary information?
FYI: I do have AutoTap, it's just that i don't want to tear mine apart to find out.
Also can someone who's fairly knowledgable in electronics build one from scratch, if given the necesary information?
FYI: I do have AutoTap, it's just that i don't want to tear mine apart to find out.
Drifting
Joined: Apr 2001
Posts: 1,763
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From: Austin TX
Re: OBDII to RS232 converter tech question. (97C5ENVY)
OBDII defines the commands that the the pcm must accept and the responses that it sends. There are three different protocols, VPW, PWM and ISO. If you want to learn how to build your own the best thing to do is buy a copy of SAE HS-3000.
I would suggest concentrating on writing your own software and buying a pre-made interface such as the ones available from http://www.multiplex-engineering.com
Thats what I did.
Eric
I would suggest concentrating on writing your own software and buying a pre-made interface such as the ones available from http://www.multiplex-engineering.com
Thats what I did.
Eric
Melting Slicks
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From: DFW TX
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Thread Starter
Melting Slicks
Joined: May 2000
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From: CenTex Texas
Re: OBDII to RS232 converter tech question. (66ImpalaLT1)
Cool!:cheers: Thanks for the info.
Is the OBDII interface connector from Multiplex-Engineering really needed? I'm asking becasue i already got the pinout for the OBDII interface to RS232 interface, and i figured i could make my own prototype connector. As far as software goes i was planning on designing my own since i'm a Software Engineer and i've done extensive work in serial communications.
Is the OBDII interface connector from Multiplex-Engineering really needed? I'm asking becasue i already got the pinout for the OBDII interface to RS232 interface, and i figured i could make my own prototype connector. As far as software goes i was planning on designing my own since i'm a Software Engineer and i've done extensive work in serial communications.
Drifting
Joined: Apr 2001
Posts: 1,763
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From: Austin TX
Re: OBDII to RS232 converter tech question. (97C5ENVY)
I'd like to see your 'pinout', because every cable I've seen requires a pic or other chip in it to translate VPW to RS232. I have one dos program with source that doesnt, it's just straight through wiring, but its very unreliable and must be run in dos because of the strict timing required for the variable pulse width communication.
I'm glad you posted today, it reminded me to order a copy of HS-3000. So far I have successfully made my Windows 2000 laptop, Linux laptop, and Palm V talk to my C5 over the multiplex engineering interface. :D I just need the books so I know all the commands to send.
Eric
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Melting Slicks
Joined: May 2000
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From: CenTex Texas
Re: OBDII to RS232 converter tech question. (66ImpalaLT1)
every cable I've seen requires a pic or other chip in it to translate VPW to RS232.
Instructor
Joined: Aug 2000
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Re: OBDII to RS232 converter tech question. (97C5ENVY)
I believe that the autotap cable interface uses a small microprocessor in it and that you woul have to right the code to talk to the software aspect. I bought a version that will not work with AT. If you look you can find a pic IC from motorola that will do the trick. However you must program the internal registers. If someone had an cable you could use a data I/o readerand program 100's and than have the program for vertualy nothing. :bb
