OBD Serial Data

[wilbo666]

The CRO looked very much like TTL RS232 to me, but indeed will have to wait and see.

That website is talking about ODB-II again. SAE J1850 is OBD-II
(http://www.interfacebus.com/Automoti...J1850_Bus.html)

ELM630 (also listed on that site) looks like a primitive CAN?...regardless it isn't what I'm investigating, it is much faster than Toyota OBD etc

Also Toyota's OBD is uni-directional; output data only!

Cheers
Wilbo

[wilbo666]

OK, I setup an old Atmel dev board I designed and never got around to using (until now) to sample the waveform (I only have an old CRO) so that I could see the waveform.



The atmel was taking a reading every 1msec and outputting it via the uart to the PC where it was logged (yes there is time to do that @ 57600Baud).

I then plotted it in excel, and then took screen shots or a section of data that looked like it was complete to put it into paint so that I could overlay a timing section to make it easier to work out the binary values. (see excel file HERE)

I then wrote the observed binary values into notepad and tried to see if I could make out the serial data format. (see text file HERE)

I only detected 14 words (the T-TEN documents say that there should be 14-20...).
[EDIT: found the 14th word (I had two number 9's!) ]

I'll have a closer look at it when I can and see how we go, I may have indeed made mistakes along the way.

Progress is being made! If others want to look at what I have so far and see if I've made mistakes etc go for it! That would be great!

Cheers
Wilbo

[brett_celicacoupe]

pic dont work man.....could be me though?

[amichie]

OK, I setup an old Atmel dev board I designed and never got around to using (until now) to sample the waveform (I only have an old CRO) so that I could see the waveform.

Hi Wilbo666

Can I just confirm with you if the engine was running or not when you collected the data?? It looks like it was not.

Could you also say if it was warmed up or stone cold.

Thanks

Andrew.

[wilbo666]

Hi Wilbo666

Can I just confirm with you if the engine was running or not when you collected the data?? It looks like it was not.

Could you also say if it was warmed up or stone cold.

Thanks

Andrew.

Not running, at room temp.

I'm assuming that the data is outputted in the same sequence that the autoshop101 doc (47) shows on the screen of the diag unit.

If my assumption is correct then the 4th data word should be RPM which should (and is that data) zero when the car isn't running!

Cheers
Wilbo

[Toobs]

I've read up a bit on this for other reasons and the older Toyota's definately use J1850-VPW protocol... J1850 is one of the protocols that can be used by OBDII but remember J1850 is just the protocol, OBDII is a complete standard that specifies what words mean what, pinouts of connectors, minimum data requirements etc.

You can read up a bit on J1850-VPW and its use in OBDII here:
http://www.systemconnection.com/down...Whitepaper.pdf

Being pre-OBD Toyota would have decided their own version of what words mean what... thus far I haven't been able to find any public listing of these but I'll keep trying.

J1850 Class II VPW protocol interface 148 is used for Chrysler, Toyota, and GM J1850 networks. The physical link is a single wire and single ended at 7V. The speed is 10.4 Kbps with CRC & message filtering in software and hardware.

Theres a ton of stuff over at iATN if you can join
http://www.iatn.net/

Can you borrow a scantool that supports the older Toyota vehicles? If so you should log the outputs to work out what the codes mean.

[wilbo666]

I'm not really interested in OBD-II at all to be honest so have tried to avoid looking at it as much as possible....

Being pre-OBD Toyota would have decided their own version of what words mean what... thus far I haven't been able to find any public listing of these but I'll keep trying.

Me either! That was why I started asking for people that worked at Toyota at the beginning of this thread...

One thing I am thinking about doing is emailing everyone listed on the following link (people that deal wil T-TEN in the USA, they should have access to the full set of docs that autoshop101 use and should be able to find the data we all want...)
http://www.toyota.com/toyota/about/locateSchools.do

Can you borrow a scantool that supports the older Toyota vehicles? If so you should log the outputs to work out what the codes mean.

Yep, really good idea; and another thing that I had in mind when I started this thread asking for people that worked at Toyota

So yep, if someone in QLD (pref near brisbane) works at Toyota and wants to lend a hand with this (access to T-TEN docs / Toyota Scan Tool) that would be tops! Otherwise poor me is going to have to work it out the hard way :S

Theres a ton of stuff over at iATN if you can join
http://www.iatn.net/

Alas I'm not eligible to join that!

Cheers
Wilbo

[Toobs]

Alas I'm not eligible to join that!

Are you sure???
Don't forget your 6 years at Toymods engineering.

[Toobs]

Also I think you missed what I meant regarding that whitepaper.
J1850 is a protocol... it is independant of OBD2 and existed prior to OBD2.
It is the protocol that toyota used.

In comparison to the internet:
OBD2 = The internet = all encompasing
TCP/IP = J1850 = the protocol

[wilbo666]

Also I think you missed what I meant regarding that whitepaper.
J1850 is a protocol... it is independant of OBD2 and existed prior to OBD2.
It is the protocol that toyota used.

In comparison to the internet:
OBD2 = The internet = all encompasing
TCP/IP = J1850 = the protocol

Yep, you are right, I did miss what you were saying. (Have seen it referenced to OBD-II a lot and hence just wanted to ignore it! )

I don't think Toyota would have used that (data rate is too high, and 94 seems like a way away from 89...)but they may indeed have used something...might as well have a look eh!

Cheers
Wilbo

[amichie]

Not running, at room temp.

I'm assuming that the data is outputted in the same sequence that the autoshop101 doc (47) shows on the screen of the diag unit.

If my assumption is correct then the 4th data word should be RPM which should (and is that data) zero when the car isn't running!

Cheers
Wilbo

That's what I was thinking to. The first two words and the last word seem to be ascii characters. All the rest are undefined and may just be numbers.

I'll read out my data over the weekend and post it up. Incidentally what model car and engine do you have. Mine is a 7mge.

[wilbo666]

That's what I was thinking to. The first two words and the last word seem to be ascii characters. All the rest are undefined and may just be numbers.

I'll read out my data over the weekend and post it up. Incidentally what model car and engine do you have. Mine is a 7mge.

Sounds good

MA61 (Irrelevant)

JZZ30 1JZ-GTE

Cheers
Wilbo

[Toobs]

I don't think Toyota would have used that (data rate is too high, and 94 seems like a way away from 89...)but they may indeed have used something...might as well have a look eh!

It's only 10.4kbps or something around that... not overly high.
It is a protocol that GM used and many others and ic's to translate are available from a heap of the semi manufacturers.

[wilbo666]

It's only 10.4kbps or something around that... not overly high.
It is a protocol that GM used and many others and ic's to translate are available from a heap of the semi manufacturers.

Have a look at the data I have already posted. It is nowhere near that fast.

The Toyota tech doucments also say that OBD is 100Baud.

Cheers
Wilbo

[amichie]

Any chance the last word was a 19 and not a 17? That would make more sense.