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Reply With QuoteIn PWM 61 6A F1 is the header.
For Can the header will be setup by the can-chip. All you do is supply a address where to send it, either 11-bit or 29-bit.
The data is the same as for any other protocol: 01 0C.
See page 22 of you manual.
J1979 CAN header question
I have interfaced to my older Ford vehicle using J1850 PWM. Now I am working on CAN in a newer vehicle. I own a copy of J1979 but am a little confused about the header for CAN PID value requests.
Here is a sample request for RPM in J1850 PWM (in hex of course):
request:
61 6A F1 01 0C crc
response:
41 6b nn 0C aa bb crc
where nn=ECU address, aa bb = DATA A and DATA B
Can anyone give me this same example in CAN?
Thanks,
Steve
In PWM 61 6A F1 is the header.
For Can the header will be setup by the can-chip. All you do is supply a address where to send it, either 11-bit or 29-bit.
The data is the same as for any other protocol: 01 0C.
See page 22 of you manual.
for 11bit its 0x7DF for the functional addressing or (typically)0x7E0 for the physical address of the Engine computer. The response from the Engine computer is typically 0x7E8.
What tool are you using to do the requesting?
I am using a Multiplex Engineering T21 card attached to my embedded microcontroller. In the future I will use the CAN module on my embedded micro.
Steve
With 11-bits can there's no guarantee that 0x7e0 is the engine.
Could be anyone from 0x7e0 through 0x7e7.
Originally Posted by p2psmurf
That's why I said typically. It has been for every car in my experience, but I know there is no guarantee.
I have done more research and study on this issue. See if this looks correct:
The CAN message for RPM:
7DF 02 01 0C
7DF = The 11 bit CAN ID
02 = 2 data bytes used out of the possible 7 CAN data bytes
01 = Service 01
0C = RPM PID
What do y'all think?
Steve
Looks good to me. Depending on how your hardware you may not need to put the 02.
Here's a sample of actual communication b/w an ElmScan 5 scan tool, and ECU Sim (as reported by ECU Sim):
Is this a commercial project?Code:7DF 02 01 00 7E8 06 41 00 88 19 10 10 7DF 02 01 1C 7E8 03 41 1C 06 7DF 02 01 01 7E8 06 41 01 83 0F EF 80 7DF 02 01 0C 7E8 04 41 0C B6 DA
Best regards,
Vitaliy
You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.
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By the way, CAN lets you increase the throughput by combining several PID requests into one, like this:
01 00 01 05 0C 0D
Vitaliy
You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.
— Did you know that MP3Car sells OBD-2 interfaces? Get your OBDLink for only $84.99!
— Need to look up a diagnostic trouble code? Try the most up-to-date, free DTCsearch.com!
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