Actually looking at those, they are just PIC's that somone programmed and is selling. I thought they were VPW specific IC's.
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Actually looking at those, they are just PIC's that somone programmed and is selling. I thought they were VPW specific IC's.
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If you take at look at my initial post:
"NOTE: I know about the ELM Electronics ELM322. (I own one) I'm looking to directly interface with the buss."
To be honest I not only have the ELM322, but I have all five of the elm devices. I was a beta tester for the most recent release. I'm interested in tying my pic to the data bus like the article did.
I own, have read, and understand the SAE documents pertaining to the communications protocol. The commands for communication are standard. (J1850) The thing at differs between manufacturers is at the physical level vpw, pwm, iso, and can. I'm just not sure how to implement vpw in PICBasic and would like to.
Last edited by DynamoBen; - 12th June 2006 at 16:47.
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I aplogize, I did research between reading your post and posting a reply. I would do it the exact same way you are proposing. It sounds like an interesting project. I would think it would work as long as you have time to send the message out on RS232 between bus messages. I don't have the protocol in front of me, and it has been a long time. I wouldn't think it would be that difficult. I would think it would really only take 4 tests. If the bus is low for long, low for short, high for long, high for short. Throw it all in a for next loop to capture the whole message. I would only be worried about missing part of the next pulse width while you are testing the previous one. It would defanitely work though if you get that aspect of the the timing down, and you don't get backed up by sending the RS232 out. I saw some VPW tranceivers out there, that seemed to make the send and receive side a little simpler. It has been a long time since I did VPW, I am more into CAN now. Hope it works out for you.
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The intention is not to do a VPW-RS232 convert, that is why I who the ELM chips. I am just interested in getting a pic onto the buss and communicating.
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receiving will be easy. Sending will be tough. You device needs to be quite when higher priority messages communicate. There has to be a VPW handler IC out there. I searched but can't find one. Only thing I can find a tranceiver. I can find them for LIN and CAN though.
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