CarBytes - MAX232 circuit

[Andrew K. Mattei]

>My only question about the transistors vs the diode, is whether Carstens
>MAX232 design will invert? the data stream.  I am hoping that its
>functionally equivalent to Andrews so I can use the LT1_Edit software with
>my own interface.

Hey Eric, sorry, I missed seeing that circuit. ;) Guess I should get out
more <G>.

I don't see why it wouldn't work. Only thing I can think of off the top of
my head is that the transistors provide a little more isolation between the
MAX232 chip and the car. The transistors also provide the driver current for
the signal to the PCM, versus in this circuit, the MAX232 is doing the
driving. I doubt it would be of any consequence, though - unless you were
using a long ALDL cable. You might check the specs on the MAX232 and see how
much current it can source/sink. Doesn't need to be much, that's for sure.
Source current in the circuit on my page is <.25 mA, and it works fine. :)

Again, sorry about the confusion!

-Andrew