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I'm trying to diagnose an issue with my '85 IROC, with it's CLCC/E4ME carb running through a 1226865 ECM.

Rather than throw random parts at it, I'm trying to build a connector to the 12-pin ALCL/ALDL port to read data from the ECM through either WinALDL or TunerPro.

Here's my thread on thirdgen.org: https://www.thirdgen.org/forums/dfi-ecm ... e-l69.html

I'm following the plans on this website, http://winaldl.joby.se/aldlcable.htm with reference to further information on this website: https://www.techedge.com.au/vehicle/ald ... serial.htm
Note that my car reads the data from Pin D, which is a quirk of the earlier ALCL's apparently. The other difference is that the data is coming out at 12V, not 5V. I assume the 10kohm resistor on the data line will deal with this, but would I be better off with a 5.1 Zener diode?

I bought a USB/TTL converter cable containing an FTDI FT232RL chip, and made this beautiful piece of a craftmanship to test it:
However, I'm getting no data whatsoever. Can anyone shed any light on why not? I've checked the COM port, baud rates, etc. All the connections to the port seem fine, and I'm getting the flickering CEL to show data being transferred. I've checked my FT232 using puTTY, and the cable seems to work, however when I tried to invert the RxD signal (which is the whole purpose of the transistor circuit, apparently) FT_PROG seems to say my FT232RL is actually a FT232/245BM, an obsolete chip that should do the same job however I've seen suggested elsewhere that it won't...

Many thanks for any help or advice,

ND

I cant really suggest anything for that circuit without putting a scope on it and seeing where the signal is getting too and at what voltage, sorry. Have a look at the 8192 baud circuit here https://www.techedge.com.au/vehicle/aldl8192/8192hw.htm it just has 160baud going straight in to T2 on a max232. I built one of those cables back in the day and used it with tech edges dos software on a 160baud vn commodore and it worked.

Also maybe try the txd pin on the usb side. Maybe they describe it as connect it to the tx pin of the other side (meaning its really the rx pin). Ive seen that before.

Hello Antus, thanks for the reply. I'm hoping not to start from scratch with a MAX232 based circuit as theoretically what I've got here should work. My circuit is roughly the same as this one from the link above:
Gargano notes that D1, Q1 and R3 are only required if reading 8192 baud, which I'm not so they're omitted from my connector. I'll admit I was slightly suspicious of the techedge information because it doesn't include the 10kohm resistor between pins A and B to trigger the diagnostic mode. It also doesn't show the 10kohm resistor to the 5V supply from the USB, which I think is needed to operate the transistor? I've tried with and without and neither yielded any data.

Of course, neither of the techedge or winALDL diagrams mention using an FT232 etc, and I'm just assuming I can wire them up the same way. I'll try using the TxD line as you suggest, and see if that does anything.

Am I right in thinking I can simply wire up to an FT232 in the same way you would a serial port? Can anyone shed any light on the differences between the FT232/245BM and FT232RL? All the data I can find seems to suggest they work the same way, although none of the FTDI utilities seem able to invert the signals on the FT232/245BM, which is a pity.

Many thanks,

ND

This analog circuitry can be a bit hit an miss. Not all cars required the 10k, i think the commodore techedge was talking about did not, which is why its not included. The sight you linked also talks about 5v and 12v circuits but I dont know anything about that. All I do know is that the max232 gives you the most voltage tolerances, and Ive used that style with success. If you want to debug the circuit you have i'd suggest getting some kind of a scope on to it so you can see the signals across the circuit and see whats going on. Otherwise its all guesswork, and I think you've tried everything.

I've used winaldl and the single transistor circuit on a serial port on 160 baud it works pretty easily usb to serial adaptor I think doesn't work in winaldl

antus wrote:This analog circuitry can be a bit hit an miss. Not all cars required the 10k, i think the commodore techedge was talking about did not, which is why its not included. The sight you linked also talks about 5v and 12v circuits but I dont know anything about that. All I do know is that the max232 gives you the most voltage tolerances, and Ive used that style with success. If you want to debug the circuit you have i'd suggest getting some kind of a scope on to it so you can see the signals across the circuit and see whats going on. Otherwise its all guesswork, and I think you've tried everything.

That's interesting point about greater voltage tolerance with the MAX232 - that might well be relevant. What about the zener diode I mentioned? If I put that on the 12V data line would that possibly make a signal compatible with the FT232? I don't know how much that would interfere with the signal.

I'm very much an amateur at this, so I don't have a scope - I'm more interested in making my car work than electronics as such!

delcowizzid wrote:I've used winaldl and the single transistor circuit on a serial port on 160 baud it works pretty easily usb to serial adaptor I think doesn't work in winaldl

I've also tried using the circuit with TunerPro, and similarly yielded no results. TunerPro doesn't recognise that the cable's attached at all.

Annoying really, I was hoping to make up this circuit so I could stop guessing at what components to throw at my car. Instead I'm faced with guessing components on this circuit instead! I'd just buy a cable but, being based in the UK, shipping and tax etc make the cables about £100/$125, hence the appeal of trying to make one.

The cable won't be recognised in tunerpro that's normal

delcowizzid wrote:The cable won't be recognised in tunerpro that's normal

Hi Delco,

Perhaps 'cable not recognised' isn't quite the right phrase. I think TunerPro recognised the cable, and established it as 'working' but didn't acknowledge any connection to the car.

I'll have another fiddle with it when I get a chance, and get back with more info.

Many thanks,

ND

Use this design try with and without r4 .I used a 2n2222a transistor back in the day and the 3904 when I made my first aldl cables .on jobys winaldl site in the vehicle list it shows what to pick for clcc cars down the bottom of the list try all 4 un till you get data. And you will need to use a real serial port not usb to serial .You should at least get some jumbled out of place data if it's outputting data and the cable is working as soon as you fit the 10k resistor and turn the ignition on the eco will just start dumping data.you could just bridge it with the 10k and scope the data pin just watch out it will be 12v