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Truck interface question

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.

Reply to
tadamsmar
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check out

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

The PID for RPM is "0C"

Eric

Reply to
Eric

" snipped-for-privacy@yahoo.com" writes: [snip]

Can't help with your questions, but what is a Sterling?

Reply to
Everett M. Greene

Uh, It's a truck.

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-- Grant Edwards grante Yow! Hand me a pair of at leather pants and a CASIO visi.com keyboard -- I'm living for today!

Reply to
Grant Edwards

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...

Reply to
Everett M. Greene

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

Reply to
PeteS

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.

Reply to
tadamsmar

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