ALDL to PC Interface Adapter

February 15, 2004: It's done and working wonderfully!!! I have designed a circuit and enclosure to allow a user to connect a PC (like a laptop) to their ALDL or OBD-I compatible vehicle. Some of the early versions had some issues with long run-time tests. This has been fixed by changing a circuit trace and a resistor. I have tested these units over night with no problems...except the car battery going dead!!

The unit measures about 2" X 2". It connects to a computer via a serial port (unlike the Diacom using the parallel port). It is based on the Maxim interface chip and includes an amplification/filtering circuit to clean up the signal from the ECM. It has been tested on ALDL and OBD-I vehicles with great results. It is also bi-directional. So if you have an ECM that receives data (like to change operating mode or even parameters), this will work.

Below are some pictures of the unit.

Couple of points of interest:

1. The use of the GM logo. I found out this really does not fly with GM and they will force me to either not use it or get a license to use their logo. So that is coming off the label.
2. Second, the current PCB version is 2.9G. If this gives the impression I have gone through many revisions, then good. Because I did! This project has been in the works for a long time. Just ask Jim Lund (he was one of my test subjects)
3. Third, there is a toggle switch with three positions: ALDL, Diagnostic and Normal/User. I think the first two are obvious. The Normal/User will cause the ECM to run as though the interface is not there. In other words, there is no resistor across pins A & B of the ALDL connector. The "/User" part may be of interest. The Normal/User position can be changed. For example, if a 3.9K resistor is placed across pins A & B of the Fiero ECM, that puts the ECM into a factory test mode. There is a spot on the circuit board where a resistor can be soldered in to change the function of the Normal/User position.

[THESE ARE CLICKABLE IMAGES]

The last picture is an earlier prototype as indicated by the "V2.9F" marking. But in that same corner is where a resistor can be placed to change the function of the "Normal/User" position of the toggle switch.

Cables

This unit uses the premade ALDL to SDL cable from AutoXray. This cable is available from Summit Racing as well as a few other places on the net. (Link to Summit Racing here) The cable can also be purchased directly from AutoXray here. In the second picture above, the connector in the middle of the unit is where the AutoXray cable is connected.

Certain computer devices do not provide enough power to run this unit (like a Palm computer), so I also added a power connector. This can be seen in the third picture to the right of the DB9 serial connector. I have not needed external power when using a laptop, but I know my old Palm V did not supply the required power. By having it there, you will never need to rig something up to make the unit work.

I wired the DB9 connector so that a simple, straight through serial male to female (like a serial extension cable) could be used. No special pin outs. Be sure the cable used has all nine pins populated! I actually use 8 of the 9.

AutoXray and Power cables.

Palm Cables

To connect to a Palm PDA, I have used (and highly recommend) Syncable Solutions. Their web site is: http://www.syncablesolutions.com. They make Palm to DB9 cables that connect to the ALDL interface adapter. The type of cable you need is their Modem Cable right at the top of the web site. With this cable, you can plug directly from the PDA into the ALDL interface adapter. I am working with Syncable Solutions about making a custom 1-foot cable for use with the ALDL adapter.

Yes, the interface adapter works with the Palm!!! I am still finishing up the software that will be given away for free to those that purchase the interface adapter.

Indicators

I utilized a 3-LED unit to show three statuses: Power (Red), Data from ECM (Yellow) and Data to PC (Green). These indicators will allow you to quickly figure out why data is not coming out of the unit. These LEDs can be seen in the first set of pictures above.

Software

This unit has been tested with WinALDL, PCMCOMM, EFI Live!, . There is also a software package coming out that works exceptionally well. It currently works on the 3800 series 1 and 2. They are testing the Fiero right now. Once this package is available, it will be all you need to have nice graphs, be able to log data, interact with the ECM. It's really slick software. It is better than Diacom or anything else I have seen. I will post here when the company releases it....oh yeah, I didn't mention one point. IT'S FREE!!!!

Update July 11, 2004 : The free Windows-based software is located at: http://www.turbo-link.com. Be sure to download vehicle pack 11 or later. This is the one that includes support for the Fiero V6.

At the same time, I am working on FreeDiag to get that working with the Fiero and other ECMs. This is free software. If I get it working, I will continue to distribute it freely. In fact, I will send my code changes back to the maintainer to hopefully have it included in new distributions.

There are a bunch of PC-related packages out on the Internet. I haven't tried them all. But it seems as soon as one works, they all do. But I am still looking for a Palm based software package. I don't think that exists yet. This interface will indeed work with a Palm. I have verified the serial data stream at the Palm and it's perfect.

Update July 18, 2004 : I have a test version of a Palm application using this interface adapter currently working. I am developing on an older Palm V as well as a newer Palm Tungsten/T2. It is working reliably on both platforms. There are some conversion bugs and some UI concerns, but I hope to have these worked out soon.

Purchasing

I am selling the unit preassembled ONLY! I am not selling kits, or the PCB. Sorry. Don't ask. If I ever decide to, I will post it here.

I can take PayPal, check or money order. PayPal ID is: steve@meisners.net

My mailing address is:

Steve Meisner
36 Marian Lane
Nashua, NH 03062

My e-mail address is steve at meisners.net

My name on Pennock's Forum (for you Fiero junkies) is "mize"

Be sure to e-mail me first to verify product lead time!!!! I solder and test these units manually...AND CAREFULLY. So there may be some delay.