I cobbled this together tonight. I used the basic schematic from here:
http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm

but changed the MAX232 output from the CTS pin to the RxD pin since that's what Andy's WinALDL seems to listen to:
http://w1.601.telia.com/~u60113744/software/winaldl/aldlcable.htm

I only built the 160 baud side of the circuit for now since I don't have any running 8192 baud cars.

Here's a pic of what I built:

Note, I'm using a 7805 powered from the car's 14.5v supply at the cigarette lighter. The MAX232 draws 10mA, so the 9.5V drop x 10mA gives me about 950mW power dissipation, that should be well within the limits of the 7805. I may put a heat sink on it just to be sure.

One question: should I connect the ground of the ALDL to the ground of the car? Is there a risk of ground plane potential difference causing current flow in the ECM where there should be none?

Look forward to your input.

JazzMan

[This message has been edited by JazzMan (edited 06-15-2003).]

[This message has been edited by JazzMan (edited 06-15-2003).] (someday I'll figure out this html thing)

[This message has been edited by JazzMan (edited 06-15-2003).]

Well crap, it didn't work. The LED I have in the output side (with a 1k resistor) is flickering, so I am getting some sort of signal out of the MAX232, but all WINALDL would do was scroll info on the PROMIDA and PROMIDB fields. I tried setting for different baud rates, different ECMs (mine should be the 7170), but to no avail My best guess is that I need to invert the signal, but does anyone else have any thoughts? Oh, there's a small square white window at the top of the WINALDL raw data screen that is not labeled, and it was flashing red with the number 5 in it. Mean anything to anyone?

Thanks!

JazzMan

Hey Jazz, I tried building an ALDL interface based on the MAX232 chip and it also did not work for some reason. However, I built a much simpler version based off 2 transistors and it works beautifully with WINALDL and DATAMASTER. Try this one:

let me know if it works for you.

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Fiero-related Conversions Performed:

1985 SE 3800 Series 1 SC 4T60-E
1987 Coupe 3800 Series II Turbocharged 4T60-E
1987 SE 3.4 TDC 5-speed
1984 Coupe SBC V8 non-OD to 4T60 OD swap, electric power steering install
1985 SE 3800 Series II Supercharged 4T60-E

http://dtcc.cz28.com

quote Originally posted by JazzMan: Well crap, it didn't work. The LED I have in the output side (with a 1k resistor) is flickering, so I am getting some sort of signal out of the MAX232, but all WINALDL would do was scroll info on the PROMIDA and PROMIDB fields. I tried setting for different baud rates, different ECMs (mine should be the 7170), but to no avail My best guess is that I need to invert the signal, but does anyone else have any thoughts? Oh, there's a small square white window at the top of the WINALDL raw data screen that is not labeled, and it was flashing red with the number 5 in it. Mean anything to anyone? Thanks! JazzMan

I'm trying to figure out what you're trying to do, here. What does the MAX232 do? (too lazy to search for spec sheet right now... )

WinALDL just needs level conversion, not conversion to RS232. It may be that by converting the ALDL serial to an RS232 standard serial, you're confusing the hell out of WinALDL, because it's expecting to see raw serial data from the ECM, suitably level-translated for the PC's serial port.

Hope that helps, at least a little

Ed

The MAX232 does not do data rate conversion, it only converts the signal voltage levels between ALDL (0-5 volts) and bipolar RS-232 (approximately +/- 8 volts). Most PCs will work fine with the simple one-transistor level shifter/inverter, but some will not. All PCs will work with the true-RS232 output of a properly wired MAX232.

You problem is most likely that you built the circuit such that the signal polarity out of the MAX232 is inverted (i.e. low when it should be high, and vice-versa). Since signal levels are all we're dealing with, you should be able to troubleshoot this with a simple voltmeter. When the ALDL output is near ground, the MAX232 output should be around +8 volts; when the ALDL output is high (around +5 volts), the MAX 232 output should be around -8 volts. You can simulate the ALDL output for testing.

Good luck.

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'88 Formula
Project Testostarossa
"Anything worth doing is worth overdoing."

[This message has been edited by Marvin McInnis (edited 06-17-2003).]

[QUOTE]Originally posted by JazzMan:

I cobbled this together tonight. I used the basic schematic from here:
[URL=http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm]QUOTE]

I will go ahead and throw my 2 cents in here.

The site that you got your info from did not work for me. It seems to be only for Austrtalian cars Or for a different ECM system.

I searched the Internet for a good month, trying a lot of different things.

I would try looking for a program called EFLive. It isn't free, but it has a schematic for a very simple interface that seems to work very well with the WinALDL program. I have been using it for about three months and have not had a problem.
http://www.autotap.com/products.html

Try that link and let us know.

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1984 SE - 30800 out of 136840. Being modified!

quote Originally posted by edhering: I'm trying to figure out what you're trying to do, here. What does the MAX232 do? (too lazy to search for spec sheet right now... ) WinALDL just needs level conversion, not conversion to RS232. It may be that by converting the ALDL serial to an RS232 standard serial, you're confusing the hell out of WinALDL, because it's expecting to see raw serial data from the ECM, suitably level-translated for the PC's serial port. Hope that helps, at least a little Ed

The MAX232 converts a square wave that's 0 to positive volts into a true RS-232 signal that's -12v to +12v, while itself only requires +5v to power it. It does this by using charge-pump capacitors. A nifty little chip that only costs a couple of bucks. WinALDL looks at the RS-232 signal on the serial port, it can't measure the voltages directly. The RS-232 decoding circuitry in the PC that manages the port does the conversion from +/- 12v to TTL.

JazzMan

quote Originally posted by JazzMan: The MAX232 converts a square wave that's 0 to positive volts into a true RS-232 signal that's -12v to +12v, while itself only requires +5v to power it. It does this by using charge-pump capacitors. A nifty little chip that only costs a couple of bucks. WinALDL looks at the RS-232 signal on the serial port, it can't measure the voltages directly. The RS-232 decoding circuitry in the PC that manages the port does the conversion from +/- 12v to TTL. JazzMan

Then it has to be, as you surmised in your last post, that you are missing the 10k diagnostic resistor....

Ed

Check out this site for ALDL interface, and software: www.euronet.nl/users/fo_elmo/techno.htm

Got it working!

It was the 10k resistor. I didn't think that it needed one, but it did in order to put it into ALDL mode.

Now I have lots of interesting data, but that's a whole 'nother thread.

JazzMan