Parallax USB-RS232 converter (DIY ALDL ODB1 cable)

[cidium]

Hi,

I am new here at the forums. I am posting here because of a project I have been working on. Long story short, I am making a OBD1 cable to connect my laptop to my 92 blazer. I found the parallax USB to serial converter and decided to use that as the heart of my cable.

Here's a look at the converter:

http://www.parallax.com/Store/Accessori ... fault.aspx

I am also using tunerpro 5, since this new to me I was wondering if any knows if tp5 and this parallax converter are compatible? My next question is if they are compatible should tp5 initialize the converter without being connected to the ALDL port on the car or does it need a to connected before it will find the converter?

thanks

[charlay86]

It should work fine as it uses an FTDI chipset.
TunerPro should be able to detect the converter without it being connected to the vehicle.

[cidium]

Well, there's my problem. I can't get tunerpro to see the cable. Got the com port set in TP, using the TP plug-in. What else needs to be setup in TP for this converter to work?

thanks

[VL400]

What plugin are you using? The native TP logging engine wont recognise it and the plugin from here (https://pcmhacking.net/forums/viewtopic.php?f=3&t=590) wont detect a blazer ECU.

If you have the one wire ALDL interface attached to it there will be echo'd data. So you should be able to use a terminal program to send data and see the echo on the screen.

[cidium]

So, are you saying TP won't work on my blazer?

92 blazer 4.3l (vin) W

[antus]

No, he is saying that our 'oseplugin' available on this site wont. That is fine, you dont need it.

Your cable will need a diode and a resistor on the tx and rx pins (not sure which way around, a search should find it), then the other end of those components connect together and to the 1 wire aldl pin on the vehicle. Then you'll need a matching adx for your car to monitor the engine.

edit: and a max232 to convert TTL to RS232 voltages!

[cidium]

Yeah, I figured that the Parallax converter would need a circuit to converter the ALDL stream to the RS232 format. You can see my project here in the Parallax forums.

http://forums.parallax.com/showthread.p ... 1-cable%29

Over at tunerpro I grabbed the datastream definition for the L35 92-94 truck. So here's the problem, after converting the ads file to adx I load it up in TP try to initialize the Parallax converter with and without the RS232 circuit attach and TP says it can't initialize the hardware. I have even had this whole setup hooked to the ALDL connecter and nothing. So, I guess starting from scratch is the best idea and was wondering if I have the Parallax converter hooked up to the laptop via the USB cable and all the drivers and com port is right should TP see the USB to RS232 converter and initialize it without being hooked to the ecm.

[antus]

Tunerpro should say it can see the cable, as it'll detect the echo. You must have an electrical fault, or configuration problem

[VL400]

Just tested a USB cable with no ECU attached and it wont recognise it - looks like TP sends out data expecting a certain response not just echo

Try a terminal program and see if your circuit echos characters back.

[cidium]

thanks everyone for the input. Going to have to test this cable later but will report back with what I find - thanks

Oh yeah, any suggestions on an alternate ALDL to RS232 circuit, maybe one that is known to work on OBD1.