pcmhacking.net

Not sure if this is helpful, from old notes I saved.


SAE J1850 PWM (pulse-width modulation — 41.6 kB/sec, standard of the Ford Motor Company)
pin 2: Bus+
pin 10: Bus–
High voltage is +5 V
Message length is restricted to 12 bytes, including CRC
Employs a multi-master arbitration scheme called 'Carrier Sense Multiple Access with Non-Destructive Arbitration' (CSMA/NDA)

In-Tech wrote:Not sure if this is helpful, from old notes I saved.


SAE J1850 PWM (pulse-width modulation — 41.6 kB/sec, standard of the Ford Motor Company)
pin 2: Bus+
pin 10: Bus–
High voltage is +5 V
Message length is restricted to 12 bytes, including CRC
Employs a multi-master arbitration scheme called 'Carrier Sense Multiple Access with Non-Destructive Arbitration' (CSMA/NDA)

Have any of your logs shown larger blocks then 12?

No, actually I have only seen 11 bytes with hyperterminal, maybe kur4o's mdi terminal will show more. Hyperterminal would buffer limit out before I could see the next block.

00 05 10 04 00 08 0B 61 00 31
64 10 F1 31 A0 00 D8 01 00 BC
C4 F1 10 7F 31 A0 00 D8 00 91
64 10 F1 27 01 48
C4 F1 10 67 01 78 79 0B F4
64 10 F1 27 02 87 41 BC
C4 F1 10 67 02 34 A3
C4 10 F1 35 01 04 00 00 20 00 92 request 1024 bytes(0400h) starting at address 002000
C4 F1 10 7F 35 01 04 00 00 0D
C4 F1 10 36 FF FA 27 FE FF FF 33 6 bytes of read at address 002000
C4 F1 10 36 FF FF FF FF FF FF 7B Continues next 6 bytes read
C4 F1 10 36 FF FF FF FF 60 20 E6
C4 F1 10 36 63 20 66 20 69 20 4A
C4 F1 10 36 6C 20 6F 20 72 20 B4
C4 F1 10 36 75 20 78 20 7D 20 9E
C4 F1 10 36 82 20 87 20 8C 20 95
C4 F1 10 36 91 20 96 20 9B 20 BE

I think this is right .bin file

I'm curious to see if after this first block, it then seed/keys again and then enters high speed mode

In-Tech wrote:kur4o, Is there a particular environment better than another. I have winXP, 7, and 10. The win10 is used for gm SPS when I have to. Does the MDI need a particular version of the "wrapper"? I am up to date on the win10 'puter, not sure what I would have to do on the others. Sorry for boring questions. Your software looks way cool. Thanks for the screenshots Mine is an original MDI(not a clone) and not an MDI2.

It will work with anything from xp to win11, any wrapper. Also from drop down list of device you can select any tool you have installed on that PC.
Usually when a tool is selected it will list all available protocols that are supported in the dropdown menu of protocol.

In-Tech wrote:I'm curious to see if after this first block, it then seed/keys again and then enters high speed mode

Wow! It literally is limited to that size. Thats incedible!
Looks like reading is pretty damn simple as well.

I think the PWM J1850 standard does actually indicate something about PWM is strictly not to be more then 11 or 12 bytes from memory.

Just to confirm, did you say it does do the seed/key again????

Tazzi wrote: Just to confirm, did you say it does do the seed/key again????

I don't know yet. I will find out when I run kur4o's program. I'll post the entire dump once I get it. That 256k .bin file I posted was a dump using Moate's J3 adapter.

I've got it all hooked up but am not picking up any traffic, HpT still works on the Y cable. I'm missing something simple.

OK, I finally got a full dump logged using PuTTY and the elm. Open in notepad or textpad.

In-Tech wrote:OK, I finally got a full dump logged using PuTTY and the elm. Open in notepad or textpad.

putty2.log

Wow.. well only 1 seed key was used. Looks like it stayed at 41.6kbps.

I can't believe how simple it is. A fucking ELM cable couple probably get the job done.
Well actually.. I take that back. I have noticed ELMs do drop packes on PWM. Their timing for the RX circuit is EXTREMELY tight, when it gets abit wrong, it drops the frame

Anyways, I will have time to work on this today after grabbing a couple more logs for Forscan dev.