Re: Q: 5V<->12V level conversion

--- In opendiag@yahoogroups.com, "Adam Bradley" <adam_j_bradley@y...>
wrote:
> And now for something completely different!
>
> http://members.optushome.com.au/adambradley/electronics/LevelConverter
> /V12/LevelConverter-v12-ajb.jpg
>

I don't know why I bother, you doesn't seem to read/understand what I
try to tell you. Oh well...

I can't figure out what you hope to accomplish with that design, but I
can tell you what it will do. It will ruin a perfectly good AVR.
Possibly the MAX 232 too. You have connected a RS232 output to a pin
on the AVR and the AVR does not respond well to the voltages involved.
The little loop with the diode may very well start to oscillate.

Was it your plan to use the MAX 232 to interface towards the K-Line?
That's definitely not a good idea. RS232 is not intended to work with
several drivers on the same line, you might end up with a bus
collision where you would possibly blow the MAX 232, or in worst case
damage the ECU. Since the K-line has multiple drivers it shall be
driven with open collector drivers. And the receiver in the MAX 232
will not reliably read (if at all) the levels on a K-Line.

> --- In opendiag@yahoogroups.com, "Adam Bradley" <adam_j_bradley@y...>
> wrote:
> > Possibly the final at
> >
> http://members.optushome.com.au/adambradley/electronics/LevelConverter
> > /V10/
> >

That design is still a mess and now it seems you've managed to invert
both TX and RX. Maybe I don't understand your application, but I'm
pretty sure that it's not the way it should be. On the other hand, if
you're going to use that particular AVR (as used in V12) you'll have
to bit bang the serial data and then you can get away with it by
inverting all data bits as well as start and stop bits and of course
the idle polarity. Quite doable, but why not follow established practice?

Honestly, apart from not being isolated, I think the inital design you
asked about (the one with only one transistor) was pretty neat. Why go
through all this trouble with designing your own?

/Henrik

 
Received on Fri Oct 24 01:48:35 2003