Parallax USB-RS232 converter (DIY ALDL ODB1 cable)

CidiumCidium Posts: 2
edited 2011-05-18 - 20:30:48 in General Discussion

I am new here at the forums. I am posting here because of a project I have been working on. Long story short, I am making a ALDL OBD1 cable to connect my laptop to my 92 blazer. I found the parallax USB to serial converter and decided to use that as the heart of my cable. In addition to the converter I used a ALDL to RS232 circuit. Here’s what I have so far...


I made the OBD1 connector and the ALDL converter circuit for the project. Here’s the schematic for the ALDL to RS232 converter...


So, can’t get a connection to the program I am using, “TunerproRT”. I need to take this one step at a time and would like to know if the circuit I have made will work with the parallax converter. Any other ideas or information would be helpful. Redesigning the whole thing is always an option.

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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2011-05-16 - 23:06:23
    A step at a time is the right approach.

    I guess you should try the ALDL to RS2332 on a computer that has an RS232 port to verify your build of that part is working properly.

    There are several free RS-232 terminal mode programs available in Windows, OS-X, and Linux, don't buy anything. Parallax provides one for at least Windows.

    After you are sure that portion is okay, then insert the USB-RS232 and use the laptop with the same RS-232 terminal mode program.
  • bill190bill190 Posts: 769
    edited 2011-05-17 - 13:48:41
    I got "WinALDL" (free) to work on my 92 GMC and using the Parallax serial to USB converter. Note that the ALDL wiring diagram on the following is different from yours above...
  • CidiumCidium Posts: 2
    edited 2011-05-17 - 20:05:38
    Thanks bill,

    which circuit did you use? Also did you use R3 on your circuit?

  • bill190bill190 Posts: 769
    edited 2011-05-18 - 20:30:48
    I used the second circuit and I am pretty sure I used the R3 resistor. (Long time ago...)
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