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Thread: OBD II and a Pic 877 toy/ford/dodge etc

  1. #1
    Newbie zonemikel's Avatar
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    OBD II and a Pic 877 toy/ford/dodge etc

    Hello everyone, havent been here for a while

    Anyway ive been searching and reading everywhere trying to figure out how to possibly get my Pic 877's to communicate with my obdII on my toyota. I also have other cars i would like to do it with but for now the toyota is the probem (1996 camry)

    Im pretty good with a pic, i can do basic stuff and debounce pull up and stuff like that, ive also gotten it to communicate via rs232. My language is C.

    How would i get the pic to communicate with the obd2 system ? What protocol is it ? in my naive head im thinking that some how i can hook up a few wires from a port on my pic to my obd2 and send data to that wire (like serial) and reset and or read the codes.

    I would be happy with something that blinks a light as to the codes, like 234 would blink twice stop blink three times stop then blink four times stop.

    Once (if) i can get it to communicate i can work making it better.

    Thanks in advance !

  2. #2
    Constant Bitrate
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    The ELM327 is actually a PIC18F248


    Luke

  3. #3
    Newbie zonemikel's Avatar
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    Quote Originally Posted by Lukeyson View Post
    The ELM327 is actually a PIC18F248


    Luke
    Ya and there are a few people that even made there own copies of the elm chip, and the elm chip is slow because it converts to ascii etc. etc.

    Ive read up on it all i just dont get how the obdII works, is it like RS232 with data and stop bits ? Any sample routines on how to send a clear code ?

    thanks

  4. #4
    Constant Bitrate
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    There are a few protocols encapsulated by OBDII. J1979 lists them.

    But SAE J1850, ISO9141, ISO14230 and ISO15765 are your next references. These standards will help you detemine the electrical and signalling definitions for each.


    Lukeyson

  5. #5
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    A good description of protocols for iso9141 (OBD11)can be found here
    http://archive.evaluationengineering...s/0398auto.htm

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