Truck interface question

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I am trying to interface to a truck's in-vehicle network using a legacy
computer.
I know nothing about in-vehicle network standards.

We bought a Dearborn Group DPA III/i to communicate via a serial line.

But I think I bought the wrong standards document (SAE j1939-71) and
I am trying to be absolutely sure that I buy the right one this time.

The truck is a 2000 Sterling L7500.  According to Dearborn, the DPA is
indicating the J1708 protocol when connected to the truck.   But I
think that
J1708 is the physical layer. I need a document that specifies the data
layer.
I have been advised that the correct standards document might be J1587.
I am not sure how to confirm that.  I have not found a technical
assistance
line a Sterling where I can confirm that this specific model or VIN
uses
J1587.

If anyone could provide the MID and PID for RPM or something every
truck should report, then I could try it.


Re: Truck interface question
check out www.scantool.net

I've bought one of these cards they work great.

The PID for RPM is "0C"

Eric


Re: Truck interface question
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Can't help with your questions, but what is a Sterling?

Re: Truck interface question
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Uh, It's a truck.

http://www.sterlingtrucks.com /

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Grant Edwards                   grante             Yow!  Hand me a pair of
                                  at               leather pants and a CASIO
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Yes, I know it's a truck.  I meant I had never heard of
such a brand and wondered from whence it comes.

I'll take a look at the Web site...

Re: Truck interface question
J1939 is a second (third?) generation protocol layer, which sometimes
co-exists with J1708. The physical layer is almost definitely going to
be CAN.
J1708 specifies the physical layer, but that is CAN.

If you want to interface directly in, then  the data protocol used (and
you asked anyway ;)
is a closely guarded secret (especially trucks). I have equipment
installed in various trucks that use the internal data, and the hoops
we had to jump through to get that information (it's not just the data
protocol, but the meaning of anything in the data layer) was
'interesting'.

On a related note, interfacing directly into the onboard systems
carries a risk you'll render the vehicle immobile.

Cheers

PeteS


Re: Truck interface question

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I hope I don't run into that problem.  I have made a little progress
and can not get the truck to report some data.  Seems to be
SAE J1587 but I will not have the SAE spec for a few days so
I cannot completely decode it.

The engine is a Cummings.  OS model I think.

We are interfacing using a Dearborn Group DPA III/I, so we
are interfacing indirectly doing that.  I don't intend to
send commands, just get data.

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