Lorenfb

"But some ecus uses different baudrates, e.g. if I switch from 993's motronic (9600bps) to the climate control(4800bps)."

Actually, the Aircable's baud rate can be changed "on the fly" via a command
without using the dip switches.

JasonAndreas

For the sizes you're dealing with the next time around it might be cheaper to order pre-cut panels (8"x11")? I've used Custom PCB in Kuala Lumpur, 2 single sided panels were $48USD.

raycm

"My question was : aren't there already some other solutions"
except for Porsche's product, I don't know of any 1995 993 OBD reader that talks to DME, CCU, Alarm, etc. Scantool that I'm using does.

As far as my interface. I stated there are a number of interfaces. I haven't tried them. I suspect they would require some mods to get them to talk to all controllers. But they are assembled with cables.

As far as scantool app is concerned, the program could be changed to eliminate the switches, work off USB, WIFI, ethernet. Why did it use serial port? A couple of years ago the serial port wasn't dying out, its happy with odd speeds, has extra control lines to use for 5 baud polling. Simple electrical interface.

I believe Data Logger stuff wants to connect to sensors. The OBD interface requires the CPU in the DME to control the engine and talk to the OBD when it has time. Not realtime for OBD data.

Ray

jjbunn

I've built the interface as specified in post #89 (thanks DougB and cowtown and others for all the info and work on this topic), but am having some difficulty getting connected.

The ScanTool (Version 4) software just flashes "Connecting" all the time.

I'm attaching to a 964's round socket:

L line (pin 7) connects to collector of Q1, (RTS)
K line (pin 8) connects to collector of Q2, emitter of Q4 (TX, RX)
+V (pin 12)
Ground (pin 10)

(I do not use any switches on my board.)

COM1 is configured for 9600 baud, 8 bits etc. - although I imagine ScanTool will configure the port the way it needs. My board is connected to COM1 over a serial cable wired as per the diagram in post #89.

Questions:

What position does the ignition key need to be in for the ScanTool to connect?

What should I be looking at (I have a 'scope) to debug what is going wrong?

Thanks!
Julian

Lorenfb

"What position does the ignition key need to be in for the ScanTool to connect?"

Run

"What should I be looking at (I have a 'scope) to debug what is going wrong?"

The LEDs as provided (made provisions for) on the original circuit (2 yrs ago) from
the NAND gates would be very helpful for situations like this. For those without
a scope, forget about troubleshooting unless one has a RS232 diagnostic LED
connector.

This is a perfect case for having LEDs on the present circuit board being produced.
So at this point, one has no idea where the problem is, i.e. Is it PC RS232 port
(or USB to RS232 if used)?, Is it the interface board?, or Is it a connection problem
at the vehicle's diagnostic connector? More thought needs to given to a more "robust"
interface circuit.

1. Check the "L" line to see that it's sending commands to the ECUs.
2. Check the DB9 to see that both TXD & RXD are functioning AND have
good levels.

Remember, the circuit (as posted recently) you're using isn't the most idea circuit
to communicate to a RS232 device, i.e. the PC.

We're obviously not at a "Plug & Play" yet!

raycm

You have a 964. You must use the 964 scantool.cfg file. It comes with the zip file. That means the DME is 8800 BPS. You can read the file with notepad.
It uses com port 1. Your pin numbers sound right. You can verify baud rate with scope as well as voltage levels.

For DME ignition is on. Engine does not need to run.
Pin L will have 5 baud wakeup signal. ~0.5V to +12V. Roughly.
The DME will respond on K pin with roughly the same levels.
Your RS232 receive pin should have the same data as pin K.
Scantool recognizes response and replies on RS232 send data.
That will also appear on K line.

If all looks right except DME isn't responding, try Climate Control or
whatever else is in scantool.cfg file. Ignition on.

Eventually one of us will compile all this stuff in a readme, including send me bucks. :-)

We could add LEDS to the PCB if cowtown wants to. But it wont be perfect, i.e. wont tell you whats wrong.

Ray

jjbunn

What would be useful is voltage measurements at various points around the circuit from someone who has built it and got it functioning.

Has the 2n3906 addition been tested, or is it just a suggestion?

Thanks!
Julian

raycm

"Has the 2n3906 addition been tested, or is it just a suggestion?"

This and all other parts of the circuit have been tested.

Ray

jjbunn

Thanks Ray :-)

I'm still investigating, having treble-checked my circuit, and the connection to the DB9 serial port plug, and the socket in the 964. I'm running a freeware diagnostic tool that monitors activity on COM1 and there is clearly nothing coming back from the 964.

Unfortunately my portable Tek 214 scope has a flat battery, so I need to fire up one of my other scopes and attach some long cables before I can look at what is happening signal-wise at the 964 socket.

I'm sure I must have a simple wiring error somewhere, but I can't see it.

Julian

cowtown

Thanks for that, Jason. That does sound much cheaper. I used expresspcb.com this time just because they give you free layout software and are here in CA. I don't have enough experience with this PCB stuff to figure out CAD tools, etc. But if there's a larger run later on, maybe someone could take my file and do a run at custompcb...? We'll see how these come out.

P-993

A copy of the software would be nice:

p7654321@hotmail.com

Thanks
Peter

Lorenfb

"Has the 2n3906 addition been tested, or is it just a suggestion?

Actually, you can leave the Q4 (2N3906) & its circuitry off and just use a 3.3K
at the base to emitter of Q3. This will provide the same noise margin and/or
threshold as the more complex Q4 circuitry, plus provides better rise/fall times
for Q3.

cowtown

Final version of the first-run PCB:
EDIT 8/11/06 - corrected orientation on a transistor.

EDIT - 8/18/06 - This is not the latest. See the end of the thread for updated layouts.

cowtown

Ray, you should see yours on Monday. I'm almost done assembling one. Quality seems very good. We can definitely condense it down to about 1/2 this size if we do another run.
Colin

maurice97C2S

Fantastic work, guys !! Can't wait for production to start ....