ALDL to RS232 to USB circuit

Thread Starter


Joined Dec 15, 2011
Hi guys,

Firstly apologies if I at first seem like a knob or some such.

I was looking for a way to plug from my car into my PC to run diagnostics, and came across this ( I have a VX Commodore) funky cable;

This funky circuit which converts it into RS232, and seeing as how I don't have an RS232 port on any of my PC's, I was going to build in this circuit with a FT232R.

Anyhow, I've come up with the following circuit (which is essentially A+B = AB) and was wondering a few things; firstly in terms of powering the circuit, originally the ALDL-RS232 portion was powered by the RS232 Port, I was wanting to swap this out for the 12v in the car, via the 78L05, will this work? I was wondering if I could use this for the USB-RS232 VCC part as well...
Or would it be easier still to keep it as is.

I realise its a little messy here, I was just wanting to put it down to make it easier for drawing up a circuit board.

Also, the CTS, RTS, and DTR , do they need to be connected at all or is this ok to leave them separate.

I think ill have other questions but I can't remember them right now, so I'll get back to them

Thanks for any help.

Last edited:


Joined Apr 24, 2011
You would be much better server if you just go out and buy an RS232 to USB converter, especially if you have one of the newer operating systems as the drivers may be obsolete.

They should be ubiquitous on the web.