J1850 PWM specs
I am trying to build my own code reader using a PIC interfaced to a laptop for J1850 PWM to use with a Ford but having a hard time finding information about the protocol. Are there any resources on the web that explain it? I have various links bookmarked that explain the general workings of it but nothing really detailed.
Yes, I realize that I have to pay for the SAE documents but I am a poor college student doing this for a school project so I can't afford it. Any help is appreciated.
I think I figured out most of the protocol but have a couple of questions still. Is the CRC byte always 0x0a?
I am going by examples here, http://www.mp3car.com/vbulletin/engi...j1850-pwm.html
Thanks for the links. I was able to get a hold of the actual SAE documentation which I found rather confusing.
Never the less I am now able to receive data from the ECM. My question now is about IFR. I think I am missing something.
Here is what's happening right now. I am sending
SOF 0x61 0x6A 0xF1 0x01 0x00 0x0A EOF
The reply I get back is
SOF 0x41 0x6B 0x10 and either nothing else or a few 0x00 bytes
What am I missing? Am I suppose to send something back after I get 0x10 byte?
Looks like I am doing something incorrectly. The response that I receive back is on the line constantly, regardless if I send anything to the ECU or not.
I guess my question would be, at what point should I be requesting data?