OBD Serial Data

[bk_]

I'm using the PICmicro (microchip).

I've checked out the datasheet... Looks like using the hardware UART would be doable. The only downside is that the crystal needs to be "downgraded" to 2 MHz, or 500 kHz for reliability, according to my calculations. I'll try out hardware UART mode in the future, if you don't get to it ;)

I wrote the code to process the data - everything works as expected. Gotta love seeing the converted temperature value and rpm ;)

-BK.

[jerryjt]

hi for everyone
that is my first post so hello for everyone and happy new year
that topic is awesome
any progres with that?
perhaps it is possible do someking scan tool as there :

http://mmcdlogger.sourceforge.net/

if you know protocol for 1jzgte engine that could be very useful in tune

Jerry

[bk_]

Hi Jerry,
I've managed to work out how to properly represent ignition angle and injector pulse width values. Updated PDF

A scan tool with graphing... The difficult thing with toyota OBD1 is that it doesn't use a standard baud rate, and most probably uses a non-standard communication protocol (eg: see the first 4 meaningless bits after serial line is made non-idle). Aswell, it's only uni-directional. Not only that, the flow of data from the ECU is extremely slow... and would only update every ~1.3 seconds.

my intention was to make a standalone device that requires no intervention to run or view. Here is a photo of my final custom once-off device: (click link for higher res)


-BK.

[wilbo666]

I haven't done anything more with this for the time being I'm afraid...

it looks like bk_ has done some nice work however!



I still don't agree with your interpretation of the OBD-I ID and word[00] tho! The stop bits don't seem to line up in that case, I think there is actually two words in that section, one 5 bits long and one 4 bits long!

IDLE-S d d d d d s s S d d d d s s
1 1 1 0 1 0 0 0 1 1 1 0 0 0 1 0 1 1

S = start bit
d = data bit
s = stop bit

Cheers
Wilbo

[jerryjt]

it is strange so it is so slow. perhaps want to much parametr wiew at once. I remember when I used MMCD software with my palm if I want see more that 4 paremetrs at one it become very slow. so perhaps there is something what say ecu witch parametrs it should send and if not it sending all parameters and why it is so slow. so perhaps it is problem


btw techtom made something for obd1 but unfortunately it is discontinued...

http://www.mkivsupra.net/vbb/showthread.php?t=13980 and pacticaly not
available
edit:
ups I read somewhere that techtom read slow too so it is not issue.

[bk_]

Wilbo,
I admit that I do not know what it is exactly right after the serial line becomes non-idle, let alone the format. We'll have to agree that we disagree :-)

One day I'll have to get a mate of mine to lend me a spare 4AGE ECU... so we can settle this issue once and for all, heh.

-BK.

[wilbo666]

it is strange so it is so slow. perhaps want to much parametr wiew at once. I remember when I used MMCD software with my palm if I want see more that 4 paremetrs at one it become very slow. so perhaps there is something what say ecu witch parametrs it should send and if not it sending all parameters and why it is so slow. so perhaps it is problem


btw techtom made something for obd1 but unfortunately it is discontinued...

http://www.mkivsupra.net/vbb/showthread.php?t=13980 and pacticaly not
available
edit:
ups I read somewhere that techtom read slow too so it is not issue.

The problem is that OBD-I doesn't have a fixed standard between car manufactures,

Also the Toyota system is uni-directional, there is no way to specify data rate or parameters to be sent back. Yes it is slow, but Toyota made it that way and there isn't anything that I'm aware of that we can do to change it!

Cheers
Wilbo

[wilbo666]

Well in the last couple of days I've made some progress,

I've got it to a stage where I'm relatively happy with what it does...

I've got a number of different display modes, depending on if I want to see it easily on the terminal or log it to a file to import into excel for later processing

bk_ is still quite a way ahead of me in terms of interpretation, and in that regards I do have a few questions...!

Q1:

0x06 Engine Coolant Temperature (ECT) See Below V See Below

What is the weighting of each binary bit in mV?! (20mV?)

Q2:
Have you confirmed that the MAP reading is in kPa?

101kpa does seem to go very close to 14.7psi so that shows promise!!
(My measurements of the 1JZ sensor vs voltage are here)

Q3:
What is your 1JZ-GTE out of?! My ecu is JZZ30 (from the identification words it looks like yours might be the same?).

Trying to work out if all 1JZ-GTE send out the same identification words or if it is ECU specific...i.e. is JZA70 different to JZZ30?!



In one of my other posts I must have trawled through all the docs and come up with the following... so I'll start trying to do some work checking what we have so far...

Unknows / Not found so far:
-intake air temperature (IAT) [OBD value?]
-target A / F (x.xxV) [Long fuel trim, pg 7-48.pdf, Signal Varies in 1.25V increments 2.5V +-1.25V, [pg 10-48.pdf])]
-a / F Fb (on /off) (Closed / open loop, On (1?) indicates closed loop [pg11-48.pdf])
-knock Retard(on / Off)
-??? others?

Notes:
-ctp Signal(on / Off) = Throttle Idle contacts?, (1) = Idle]

Page3 47.pdf
-injector(x.xmsec)
-ignition(xxdeg Ca)
-iac Step#(xx)
-engine Spd(xxxxrpm) Res 50rpm(guess 255 * 50 - > 12750?) [25rpm -> 6375]
-vaf(x.xxv)
-ect(xxxdeg F)
-throttle(xdeg) Res - > 0.5deg (guess )
-vechicle Spd(xxmph) Res - > 1kp
-target A / F L(x.xxv) (2.50V +-1.25V)
-target A / F R(x.xxv) (2.50V +-1.25V)
-a / F Fb Left(on / Off)
-knock Retard(on / Off)
-a / F Fb Right(on / Off)
-sta Signal(on / Off)
-ctp Signal(on / Off)
-a / C Signal(on / Off)

Page9 47.pdf
-injector(x.xmsec)
-igniton(xxdeg Ca)
-isc Step#(xx)
-engine Spd(xxxxrpm)
-airflow(x.xxv)
-coolant(xxdeg F)
-throttle(xdeg)
-vehicle Spd(xxmph)
-target A / F L(x.xxv)
-target A / F R(x.xxv)
-a / F Fb Left(off)
-knock Retard(off)

One of my Terminal views...



Cheers
Wilbo

[jerryjt]

great! wilbo what interface you use?

[wilbo666]

Went for a little drive the other day, nothing real exciting to report, all seems to pretty well work

I'll start on my interpretation of values bit next I think What I'd really like is to be able to use the front end of an existing program to display my values!, i.e. megaview etc...

great! wilbo what interface you use?

Not sure what you mean? My thing sends the data out serial to a PC atm, and I log it via hyper terminal

Cheers
Wilbo

[takai]

Hm, im quite interested in this and cant believe i missed it the first time. Hopefully ill have a chance to play around with my 2JZGE stuff in the near future.

[jerryjt]

sorry
perhaps my questions are stupid but I am not very familiar with that stuff.
but I need toyota obd1 reader. I have some strange issues with my soarer, so perhaps that reader will help me much.

I just wonder what is need to read data stream? I assume your program (that is named hyper terminal, correct?) and some kind of cable to connect to diagnostic port and laptop. And that cable I call interface.
best wishes
Jerry

[wilbo666]

sorry
perhaps my questions are stupid but I am not very familiar with that stuff.
but I need toyota obd1 reader. I have some strange issues with my soarer, so perhaps that reader will help me much.

I just wonder what is need to read data stream? I assume your program (that is named hyper terminal, correct?) and some kind of cable to connect to diagnostic port and laptop. And that cable I call interface.
best wishes
Jerry

Oh, not quite.

I'm using a small microcontroller (Atmel) to read the data from the car, and then send it to the PC.

Hyperterminal is a windows program shows the data coming from the microcontroller. Hyperterminal comes with windows, I didn't make it

Cheers
Wilbo

[jerryjt]

is there any possibiltes buy from you that program and that cable?
thanks
Jerry

[jerryjt]

is thereany news for OBD serial data?
be honest I need only long and short trims readings to tune my car with EMU