Quote: Originally Posted by
reece146 
I was talking to a vendor about my project and they stated that their ODB-II cable is not meant for "permanently connecting" a car PC to the OBD-II port.
It all depends on the quality of the wiring, the interface, the software, and the car. Lousy wiring can act like a giant antenna that injects noise and corruption into the network. Lousy tools will do the same thing, or worse they carry voltage spikes and blow out your PC. Lots of cars are robust, but some cars are so touchy that anything out-of-spec pushes them over the edge.
Other vendors will stand by their equipment for semi-permanant installation, rough conditions, etc. Look around a little more before you settle on a solution.
Quote: Originally Posted by
reece146 I can see the point regarding the whole baud change negotiation thing at initial but...
The ECU should spend its time running the engine and refuse commands or delay responses when its busy. Of course there are a few buggy ECUs as exceptions to the rule (often solved by a flash update!). BUT.... If you both you and the ECU follow the protocol, distance limitations, and electrical specifications then it will work just as well as it was designed to work.
Generic OBD-II has no negotiation and fixed baud rates. You may be thinking of ISO which has an unusual init sequence (a few bytes at 5 baud) and drops out of diagnostic mode with 5 seconds of no activity. Seems overly cautious in hindsight.
Quote: Originally Posted by
reece146 Is the vendor just being overly cautious or is there a type of cable that is meant for permanent connection? Some kind of a buffered assembly that keeps the conversation with the ECU/PCM "clean" for the PC?
He knows his equipment best. If it's a cheapie solution its possible that they cut corners or don't spend the time to formally test and validate things. I really can't argue with somebody who says "don't use my equipment for this"
There are a million ways to break the rules so there's no buffer, filter, or magic fairy dust to stick in the middle and improve the situation. My only thought is to use different equipment and software where the vendor stands by the solution for semi-permanent installation.
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