Uber-easy DIY USB ALDL Cable

[RobertISaar]

http://dx.com/p/12-pin-to-16-pin-obd...rs-10cm-115651

that's what i use.... kind of stubby, but it works.

[phonedawgz]

Your best bet is here - http://aldlcable.com/sc/details.asp?item=daewoo

That way you know you have all the conductors that are needed. A lot of the OBD1 junk out there don't have wires on all the pins that are normally used.

[RobertISaar]

the one i linked to has all 12 pins connected with seperate circuits.

[Playtoy_18]

Just to confirm the unbelievable simplicity to making this aldl cable, Hopefully a small image with red circles will help anyone else with the same question!


Solder the Rxd and Txd together, solder single wire from that to communication pin on Diagnostic plug.
Then solder wire from Gnd to ground pin on plug.
And obviously keep the bridge over VCC and 5V or solder together if intending to keep it like that.
That about cover it for 8192 baud communication?


Still cant believe aldl cable can be made for ~$20!. Paid $80 for my last one!

Awesome post,thanks for the pic.

I think I might have what's needed onhand.
I needed a usb/ttl convertor for a subaru cable for a buddy and happened to order 3 since I figured they might come in handy (and they were like $3).
I also have an old OTC mindreader scantool that no longer likes to read OBDI.
So i'm gonna put this thing together and see if I can get it to talk to my 91 caprice.
If so,that means I don't need to buy one and can throw money at a burner.
mucho appreciado muchacho's.

[Playtoy_18]

Okay,got as far as tinning all the connections to solder together and wanted to clarify something.
I still need to make the circuit using the transistor and resistors and then the tx/rx/grd goes to the usb/ttl adapter right?

I'm converting from ecm to serial with the transistor circuit,and the adaptor is converting from serial to usb correct?

I'm assuming the cable does not have that already built in,I have no idea how the otc talks to the ecm.

[RobertISaar]

depends on your adapter. if it is TTL to USB converter, then no external components are needed.

what kind of chip is doing the work? with odd baud rates, only the FT232 chips seem to work reliably.

[Playtoy_18]

I'm guessing PL2303HX ?

Description:
This PL2303HX USB to TTL converter module is a must for simple serial communication and allows you to upgrade the firmware of your router or ADSL modem.


Features:
Easy serial communication
Upgrade your router or ADSL modem's firmware
Simplify connections: RX to TX or TX to PX of an MCU. Then connect your GND, without the need for MAX232
GPS serial communication
Use as a serial debugging tool for the hyperterminal
Upgrade your hard disk's firmware
Upgrade various satellite receivers


Note:The color of Dupont Wire is random when we dispatch it.


Package includes:
1 x USB to TTL Module
1 x Dupont Wire

Never mind,I think it says right in the description.
I had gathered that the transistor/resistor circuit was what everyone was calling max232?

[RobertISaar]

with a 160 baud application, it might work, but i can't really guarantee it, i know the 2303 chip doesn't like 8192 baud at all.

MAX232 is an IC to help convert signals to and from RS232 specification.

[Playtoy_18]

A 7747 is 160 baud right?
That is what I need it for right now to get me by till one of your cables are ready

[phonedawgz]

Yes 1227747 = 160 baud

[fas000]

HI. Great Thread. Is it possible to do anything with this one?
http://www.ebay.com/itm/380599351265...84.m1438.l2649
or this one:
http://www.ebay.com/itm/300771847336...84.m1438.l2649

[RobertISaar]

the second would probably be able to be used after some workarounds(since it uses the FT232RL), but i really don't know bluetooth that well.

the first, i can't get a clear image of the ICs used, but if it's not a FT232R, don't expect it to work at GM OBD1 speeds.

[Playtoy_18]

So mine would be tx/rx tied to pin E for data,ground to ground/pin A and tie VcC/5V together on the convertor then right?
Then load up tunerpro and try to find a driver to work?

seems too simple,i'm forgetting something.
hope it works,if not need to order a cable from somewhere quick.

can someone smarter confirm?

[phonedawgz]

Start with not connecting VCC to 5v. Normally that isn't needed, but you are using a different board so idk. If you have no lights at all when you are plugged into the USB only then do it, but if you get lights, then it is not needed.

You might need the 10K resistor between A - B to activate this output of the ECM.

[EagleMark]

1227747 = No 10k...