Parallax USB-RS232 converter (DIY ALDL ODB1 cable)

[kojab]

https://pcmhacking.net/forums/view ... f=14&t=622

Works great.

[cidium]

Update:

I connected pins 2 and 3 together on the Parallax RS232 connector to create a loop back route. Opened up TP and went into the plugin config and used the test cable option. It passed the test so the Parallax converter is working, also tried it without the jumper wire between pins 2 and 3 and got a failed response from the cable test. So, now it seems the ALDL to RS232 circuit I made is not connecting the ECM to the Parallax converter. I could use a diagram for a known good circuit to convert the ALDL to RS232.


Here are the specs on the ECM

16156647
Application: 1992-93 truck 2.5 L4 TBI “A” L38
1992 truck 4.3 V6 CPI “W” L35
1994 truck 4.3 V6 CPI “W” L35 w/ MT
MEMCAL IDs: “A”: …
“W”: BAWP, BCBH, …
EPROM type: 27C256

I just tried a simple read-only ALDL to RS232 circuit and same thing, not connecting. " Note that Q1, D1 and R3 are not necessary if only 160 baud ALDL data is to be read. However, if the faster (and bi-directional) 8192 baud ALDL data stream is to be read, then the complete circuit as shown here is required. " What I did was make the circuit without Q1,D1 and R3. From what I read the 160 and 8192 baud pins share the same line to the ECM, so the difference between each circuit as far as I can tell, is if you need to "send" data.



So I got a a few questions.

When does TP connect to hardware - bottom screen where it says hardware not connect. I can see TP trying to initialize the hardware but always returns "not connected".

When the ADX file is loaded into TP does it show any parameters or does the program stay blank till data is received? When I load the ADX file into TP nothing changes, everything is blank.

How can I confirm I have the right ADX file for my truck? http://tunerpro.net/gmOBDI.htm A178

Does anyone know if this ECM needs a resistor between pin A and B to start the send data?

The circuit I made is using pin M (8192 baud) on the ALDL connector, should I be using the 160 pin?

thanks~

[VL400]

One thing that may be an issue, not sure as I have never used the hardware your using, is that the ALDL circuit is not really RS232 compliant. RS232 also has negative voltages which the circuit your using does not have. Some RS232 chips dont have a problem with that though.

The initialise hardware is for say a moates ostrich or OSE plugin and 12P ECU code. When you press the initialise hardware it goes off and tries to identify the device that is connected. You interface wont return any valid data, just the echo'd bytes.

The ADX just defines the data stream so the data will just have blanks or depending on the calculation a static value. On early 160baud vehicles you had to use a resistor to get data happening. On all aussie cars that are 8192baud you have to request data, i know some US cars that are 8192baud still needed a resistor to get data transmitting. Might need to measure the ALDL line with a multimeter and see if the voltage changes when you bridge pins A and B.

[cidium]

My copy, downloaded from their website, of TP has half the help file is missing. Since I have never used TP before I don't know what a working session in TP looks like besides the sensor data is displayed. So what I need to know is what does a the screen look like after you load the ADX file?

Like this-


Or like this -


And..I got another cable today:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... &viewitem=

So I hope this is ready to work.

[VL400]

TP will look different depending on what the ADX has defined and what you have selected to view. Have attached a modified version of your screen shot showing which buttons change the display.

Your new cable is using the Prolific PL2303 chipset which can be a little hard to setup .. https://pcmhacking.net/forums/viewtopi ... 592&p=6993

[cidium]

So, concerning TP, once I load the ADX I should be able to hit connect and data should flow? I don't need to do anything else but set the com port for my cable?

With this new cable I hook the ground to ground and the RX to the (M) pin on the OB1 connector and it should send data?

[VL400]

If you have a known working ADX for your model vehicle and a known working ALDL interface then yes thats all.

You still need to make a ALDL conversion circuit, cant just hook the Rx of the interface to the ALDL bus.

[malser]

VL400 right! To connect to the vehicle you need ALDL to RS232 circuit and RS232 Port of home computers, or ALDL to RS232 - RS232-USB- converter - USB Port of home computers. Directly without ALDL to RS232 to connect fail. Remember that the RX must be connected to the TX , and TX must be connected to the RX.
Sorry for my English.

[cidium]

Ummm, does anyone have a circuit diagram or know of one that I can look at. I know there are a few out there but I am getting tired of F'ing around, just need something that is going to work.

[antus]

This is what I use on the test bench. Simple ebay max232 circuit, and a 1k resistor and a generic diode. In this case im powering the max232 board from the ecu's 5v line as its not a in a car. You might need to regulate 12v down to 5v from the aldl connector in your car in your case.

Its based on the 8192 baud portion of this: http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm but note that the diode is backwards in that diagram. It should be orientated as in my pic (line on the diode is car side, away from the max232).