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Thread: ELM329 custom USB interface

  1. #1
    Newbie reinoso's Avatar
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    ELM329 custom USB interface

    Hello,

    I have designed a custom PCB with ELM329. It has two CAN transceivers, microchip MPC2551 for HSCAN and Melexis TH8056 for SWCAN. This board is specially designed for GMLAN cars.

    You can switch between HSCAN and SWCAN sending the AT C0/C1 command.

    I can't wait to start sending AT commands on my SAAB 93 MY2005



    In the picture MCP2551 was not soldered yet. USB to UART IC is FT232BL.



    Hope you like.
    Last edited by reinoso; 10-31-2011 at 03:02 PM.

  2. #2
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    tripzero's Avatar
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    Very awesome. Sounds like you've made it easy to switch between hscan and swcan. Does it automatically know the protocol to use for these or do you have to use the ELM AT commands to set the protocol/baud/etc?
    Former author of LinuxICE, nghost, nobdy.
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  3. #3
    Newbie reinoso's Avatar
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    you have to set the protocol and baud rate manually, as you would do with ELM327 based devices.

    This board only has a hardware switch that routes CANTX and CANRX to the corresponding transceiver. This hardware switch is controlled using AT C0/C1 command.

    AT C0 = MCP2551 (HSCAN, default)
    AT C1 = TH8056 (SWCAN)

  4. #4
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    I guess the next big question on the lips of many is will you be producing these items for purchase or can we get a BOM and the PCB file.

    thanks
    Michael

  5. #5
    Newbie reinoso's Avatar
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    I had not planned to sell this board, but if many people is interested, I'd consider to make a few.

    Well, today I spent a few hours doing some sniffing. I identified the code for activating ligths, wipers, etc.

    I forwarded the data packet and all work OK, but only for a while (ie. wipers are activated only for a second). It is normal because the original ECU is also sending the "OFF" packet periodically.

    My question is, if I want to make my own circuit to turn the lights on without using the original button, Do I have to always be sending the "ON" packet faster than original ECU? I don't like this "bus fight", is there any way to avoid this situation?

    Thanks

  6. #6
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    I don't think you can avoid the fight. You are essentially spoofing the message from the module that controls the wipers. You'll probably have to listen for the "off" from the original module and immediately issue an "On".

    I don't understand how this hardware differs from say a obdpro scantool that's modified to work on the swcan bus. Can you illustrate the difference?
    Former author of LinuxICE, nghost, nobdy.
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  7. #7
    Newbie reinoso's Avatar
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    Thanks for the answer tripzero.

    Doors lock work in that way too??? Or there is only a packet for ON and other for OFF, and no periodically "reminders"

    Thanks

  8. #8
    Newbie reinoso's Avatar
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    Quote Originally Posted by tripzero View Post
    I don't understand how this hardware differs from say a obdpro scantool that's modified to work on the swcan bus. Can you illustrate the difference?
    It is simple, it has a SWCAN transceiver attached to ELM device: Melexis TH8056.

  9. #9
    VENDOR - ScanTool Vitaliy's Avatar
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    Do you use a custom pinout for your OBD to DB9 cable?
    OBDLink MX: world's smallest, fastest, most advanced OBD/Bluetooth adapter with SW and MS CAN support. Read the review to learn more.
    Need to look up a diagnostic trouble code? Try the most up-to-date, free DTCsearch.com!

    You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.

  10. #10
    Newbie reinoso's Avatar
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    Quote Originally Posted by Vitaliy View Post
    Do you use a custom pinout for your OBD to DB9 cable?
    Yes.

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