rockstar08

I've wired a 2 transistor cable using the design below.

I am experienced with RS232, and soldering cables, I've double checked my soldering and its sound. The only modification I have made is to wire R2 to pin 4 on the 9pin serial connector, which is hot at 6V from a usb-serial cable.

Ive tried Datamaster, Freescan, and EFI Live, with no success.

I want to make the cable myself, and not buy an off the shelf one.

I'm connecting it to my 1990 350TPI Camaro.

Has anyone had any success making their own cables? if so what design and software did you use?

Any suggestions greatly appreciated...

Dizturbed One

I'm trying to figure out the same, so would be very interested to see someone reply in here.

rockstar08

So I've tried the same 2 transistor cable on 2 different laptops, one with onboard rs232 the other with a usb-serial cable. Both have DTR pin at 6V.

I have also re-configured the cable exactly as per the diagram with +12v from the lighter socket, verified with a multimeter.

I have tried with and without a 10Kohm resistor across the top row rightmost pins.

When i open hyperterminal i setup 9600-8-n-1 on my com port. The only data i see is sent when the ignition is turned off, its a "o" character..

I've built another cable using max232 chips taken from here..

http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm

after building and testing the circuit i found that the 78L05 is wired incorrectly on the diagram, as pin 2 is the ground ( the diag shows pin 3 ) despite checking against the datasheets from the silicon makers, and testing on two different laptops. It produces the same result as the two transistor.

It seems as if the ECU/ECM is not sending ALDL data to the port. Again I have tried to use a 10K resisitor.

Any suggestions really welcome!

snardos

I used the same diagram as in the first post. I rebuilt it twice when it didn't work. The problem was that I was using a usb to serial converter. I got a free old laptop with an actual serial port and it worked right away. I am using tunerpro RT to datalog. The usb converter works fine with other equipment but not with this circuit.

Dizturbed One

so does that mean you have to have a serial port for ALL of the homegrown cables?

am i doomed to buying one because my laptop is too new?

rockstar08

I wouldn't think so. The ones you can buy use off-the-shelf components, just like the home grown ones. It should just be a matter of the right cable design and a suitable usb-serial converter cable.

As I understand, the UART of the serial port must be able to handle 8200 Baud or close to it and the cable must be able to switch the voltages from the 3v ECU/ECM to the 5-12v voltages used in RS2322. That's basically what the MAX232 chips do. The 2 transistor cables are just switching the 12v from the battery to the rs232 send & receive pins, based on aldl low & high voltages.. this design is flaky at best...

I'm gonna throw together another cable this weekend, and use a more generic max232 circuit that Ive had success with on other projects. I have an old laptop with a serial port. If I can get that to work with that then I'm sure I can get a usb-serial cable to work with it.

I believe my problem is that the ECU isn't sending data. I need the equivalent of a breakout box for ALDL to diagnose. I'll try and build one this weekend.

Will post my success/failure ..

RBob

iTrader: (1)

For your '90 TPI Camaro you need to send a data request to the ECM. Then it will send a packet of data. Otherwise the ECM won't be sending any data.

Note that various ECMs handle this differently. There are ECMs that send data all of the time (TBI), and ones that send chatter ('90-'92) MPFI.

RBob.

rockstar08

Swwwweeeeetttt.. got it working.. the interface now works very well.. with both interfaces listed on my earlier postings..

The problem was 3 fold~

1) The serial to usb converter I was using was not capable of selecting 8200Baud. This was also the case on the old laptop I was using.. The reason it will work on most old laptops is that they have compatible 'programmable' 16550 serial uart controllers, with these old things you can set a custom baud rate. With the more modern onboard serial ports you cannot, hence they don't work & don't produce any error message when selecting a non standard rate.

The simple solution is to buy a compatible usb-serial adapter, this one is available at frys electronics and I can confirm it works on VISTA & XP!

Parallax FTDI based usb-serial adaptor. Its also the same type thats used in moates and aldlcable.com cables. The benefit of this one is that it has 2 activity leds that actually show you its working.. red for receive from car and green for activity to car.

You can buy it from here:-
http://www.frys.com/product/5229677?...H:MAIN_RSLT_PG

Before connecting it to your laptop be sure to install the drivers from FTDI.com first! http://www.ftdichip.com/Drivers/VCP.htm

This is great if you want to ditch that old laptop, with a dead battery, and use new one with USB!

2) The max232 circuit was incorrectly diagrammed. The 78L05 had the incorrect pin identified as ground, this is pin 2 not pin 3.

I built this one : http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm
but switched pins 2 & 3 on the 78L05 to fix the fault..

3) My ecu, the 7730 requires ALDL dump string to initiate the flow of data.

The software I tried, EFI Live, Freescan and Datamaster all didn't do this out of the box.

I downloaded Tunerpro RT from here .. http://www.tunerpro.net/downloadApp.htm

And the correct definition .ads and .ecu from here http://www.tunerpro.net/downloadBinDefs.htm for my 7730 ecu.

After starting Tunerpro RT,

a) Go to preferences and configure your com port. ( You can get the com port number by right clicking on my computer from the start menu and selecting device manager, com ports )
b) Go to XDF..import..From ECU.. open your ECU file you downloaded from Tunerpro.
c) Go to tools..ALDL datalogging.. open the ads file..

Connect your ALDL cable to your usb-serial cable. Turn on your ignition.

This gives you a window with the option to "send command" in the bottom left corner of the window. Click it.. this sends the string that initiates the data flow from the ECM.

Then click to connect to ecm! The green and red lights on your USB-serial adapter should light up, showing the data flow.

If all goes well, select ALDL dash in TunerPro and you'll see the data flowing from your ECU.

Hope someone finds this useful, and thanks to everyone who has posted replies!

If anyone has any good sites/books/recommendations on how to learn ECM/U tuning, please let me know!