Re: OBD II Interface

 and what the hell is OBD2 ?

--- In jallist@yahoogroups.com, Stef Mientki  wrote:
> hello Shawn,
> 
> very interesting,
> I just saw that Elektuur / Elektor has also a OBD-2 controller 
based on 
> the T89C51,
> they support ISO9141-2, KWP2000, J1850-PWM, J1850-VPWM, CAN bus 
(ISO 
> 15765-1..4).
> There are also a lot of links in Elektuur (haven't checked them).
> 
> Do you have already hardware schematics ?
> I like your idea of having a standalone device (elektuur uses a 
serial 
> port to a PC).
> 
> cheers,
> Stef
> 
> sstandfast wrote:
> 
> >If anyone is interested I am currently working on building a stand-
> >alone, hand-held OBD II interface using the F877.  Sorry, as of 
right 
> >now the only protocols it will support is the GM VPW as this is 
the 
> >only protocol that I have found suffient (free) information on.  
Mind 
> >you, this is a work in progress and is only about 3/8 of the way 
> >finished but I think I have most of the hard stuff done.  Currently
> >the 
> >code supports the CSMA/CR VPW protocol defined in the SAE J1850
> >specs.  
> >Routines for generating a complete OBD II message Frame are 
provided.
> > 
> >However, I still have to fully impliment a data receive 
structure.  A 
> >loosely implimented receive is embedded but it is no where near
> >perfect.
> >
> >The current JAL code can be found on my website 
> >

 as well as a slightly more
> >detailed 
> >description of the project goals and (eventual) features.  The 
source 
> >code is fairly well commented for ease of logic flow but all
> >questions 
> >are welcome.  Also, feel free to make suggestions or comments.
> >
> >By the way, if anyone on here has any hints as to how I can buffer 
> >multiple frames each containing an unknown number of bytes without 
a 
> >fixed amount of time before the next frame is received I am all 
ears.
> > 
> >Currently, each byte in a frame is shifted in one bit at a time 
and 
> >stored in an array.  A flag bit is then raised indicating 
processing
> >is 
> >required in the main loop.  However, in the J1850 protocol, there 
is
> >no 
> >fixed latency between frames so I run the risk of losing or
> >corrupting 
> >the last frame received if the next frame is received before the 
last 
> >one could be processed. I have an idea on what to do but it 
involves 
> >looping within an ISR.  Something I have been told should be 
avoided
> >if 
> >possible.
> >
> >Hope somebody finds my work thus far useful, and thank you in 
advance 
> >for any tips.
> >
> >Shawn
> >sstandfast@y...
> >
> >
> >
> >
> >