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Thread: serial port cable that goes to v2

  1. #11
    Joe (Moderator) joecar's Avatar
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    Howard,

    Look at this diagram (for the LC-1), the null modem connects 2 to 3 in both directions...

    i.e. the null modem adapter connects Tx->Rx in both directions.
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    Last edited by joecar; November 27th, 2009 at 08:12 PM.

  2. #12

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    Quote Originally Posted by joecar View Post
    Howard,

    Look at this diagram (for the LC-1), the null modem connects 2 to 3 in both directions...

    i.e. the null modem adapter connects Tx->Rx in both directions.
    Joe,

    I see that but I am not seeing that the ECM unit uses the same pins as the LC-1. What am I missing??

    What is the purpose of a null modem? Isn't it critical that Tx go to Tx or is it Tx to Rx and Rx to Tx.....respectfully....

    I just want to make sure I'm wired correct before I try and get this trace captured.

    Thanks

    Howard

    www.redline-motorsports.net

    1-954-703-5560

    2006 ZO6 895/866 with APS TT
    2010 SSRS Camaro HTR-900TT (798/801)
    2011 HTR-850R Camaro
    2012 ZL1 Auto (10.33@135 MPH) Video Here!

  3. #13
    Joe (Moderator) joecar's Avatar
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    Howard,

    The transmit circuit (Tx) of one device must drive the receive circuit (Rx) of the other device...

    If you can connect each of the wideband and/or FSV2 directly to a PC,
    then you need to cross the Rx and Tx signals when connecting wideband and FSV2 to each other.

    Sorry, I had some stupid typos in my post, I corrected them, reread post #12


    Sorry I couldn't call earlier enough today, we had my in-laws over and they stayed very late...

    Joe

  4. #14

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    Hey Joe,

    No problem...holiday weekend I can understand!

    If you can take a look at page 16 of that AFM1500 manual. It notes the pin configuration. However it looks correct to match the pins going to the PC but not correct leaving the module. Before I order some RS-232 ends and hot wire my own conversion harness I want to confirm I it needs to be done. Would think that serial RS-232 would be the same standard.

    Man this is stumping me!

    HT

    www.redline-motorsports.net

    1-954-703-5560

    2006 ZO6 895/866 with APS TT
    2010 SSRS Camaro HTR-900TT (798/801)
    2011 HTR-850R Camaro
    2012 ZL1 Auto (10.33@135 MPH) Video Here!

  5. #15
    Joe (Moderator) joecar's Avatar
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    Default Reposted with corrections...

    Summarizing from mr.prick's link (that's a very good link, thanks):

    There are two types of serial equipment:
    - DTE (data terminal equipment) e.g. computers, printers.
    - DCE (data communications equipment) e.g. modems, wideband, FlashScanV2.

    DCE devices can connect directly to DTE devices without Tx/Rx crossover.

    Tx is the device's serial output (on which it sends out serial data).
    Rx is the device's serial input (on which it receives in serial data).

    Wideband and V2 are both DCE (transmit = Rx, receive = Tx)...
    so somewhere in between them this has to be done (this is what the null modem adapter does, crosses Rx and Tx):
    wb.Rx ---> V2.Tx
    wb.Tx <--- V2.Rx

    (see post #19 below)

    See the attached diagram (I added some labels).
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by joecar; July 21st, 2016 at 06:36 PM.

  6. #16
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Redline Motorsports View Post
    ...
    If you can take a look at page 16 of that AFM1500 manual. It notes the pin configuration. However it looks correct to match the pins going to the PC but not correct leaving the module. Before I order some RS-232 ends and hot wire my own conversion harness I want to confirm I it needs to be done. Would think that serial RS-232 would be the same standard.
    ...
    Howard,

    Does the AFM connect directly to a PC using the AFM DB9 cable...? If it does, then the AFM is DCE.

    FSV2 is DCE.

    So to connect two DCE devices, Tx/Rx crossover is required (i.e. this is what the null-modem adapter does).

  7. #17

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    Quote Originally Posted by joecar View Post
    Howard,

    Does the AFM connect directly to a PC via the DB9 cable...?
    It came with a cable that is to tie in with other ECM modules. If I understand the pin config from them it appears that must have some proprietary system for it to work.

    If I just get the;

    Tx > RX
    Rx > Tx
    Grnd=Grnd

    That should be it....correct? If that is the case I don't think the null modem works. Now I just want to confirm I understand which pins on the ECM box are what. You already posted the EFIL serial cable so this is the last link.

    www.redline-motorsports.net

    1-954-703-5560

    2006 ZO6 895/866 with APS TT
    2010 SSRS Camaro HTR-900TT (798/801)
    2011 HTR-850R Camaro
    2012 ZL1 Auto (10.33@135 MPH) Video Here!

  8. #18
    Joe (Moderator) joecar's Avatar
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    RS232 is a standard, but what makes it confusing is that the Rx and Tx signals are mis-named on one of DTE or DCE (I'm not sure which one).

    I'm not sure what ECM have done exactly.

  9. #19
    Joe (Moderator) joecar's Avatar
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    More info:
    http://www.bb-elec.com/tech_articles...tions_work.asp
    http://digital.ni.com/public.nsf/all...256F720071DECF


    Edit: on that website, on all instances of DCE connector, it shows: Tx receives data, Rx transmits data.

    On that page, scroll down to "Modem to Modem Cable" / "DCE to DCE"...


    See this pic, look at pins #2 and #3, look at the directions of the red and green arrows:
    Click image for larger version. 

Name:	DCE-DCE null-modem.jpg 
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    On DCE devices: Tx receives data, Rx transmits data.

    Confusing to say the least...
    Last edited by joecar; July 21st, 2016 at 06:42 PM.

  10. #20
    Joe (Moderator) joecar's Avatar
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    Howard,

    Try this:
    - connect the AFM to your PC's serial port using the null-modem adapter,
    - go Start->All Programs->Accessories->Communications->Hyper Terminal,
    - enter any name (AFM),
    - click OK,
    - enter any area code and phone number (111 2223333),
    - set Connect Using to COM1 (or whatever your PC's COM port is),
    - click OK,
    - set 38400 baud, 8 Data Bits, Parity None, 1 Stop bit, Flow Control None (from the AFM manual),
    - click OK,
    - now you should be in the terminal window...

    In the terminal window you should see stuff being printed... if not then remove the null-modem adapter.

    If it still doesn't print, shutdown HyperTerm and restart it, this time specify the other COM port (e.g. COM3), and try again with and without the null-modem adapter.

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