Am Donnerstag, 1. Februar 2007 00:39 schrieb George M. Zouganelis:
> Simon Natterer wrote on 1/2/2007 01:16:
> > George M. Zouganelis wrote:
> >> Today I built a DS2480 serial adapter (schematic attached) after
> >> failing to work with
> >> a orginal Elektor schematic (wich had no RS232 level Driver)(Issue
> >> Apr/2004 By Luc Lemmens)
> >
> > I have almost the same schematic, but with a MAX232 and there I have to
> > tie the POL pin to +5V (VDD). I don't know what is the difference of
> > your ADM232.
>
> Arghhhh!!!! ^^^^^^^^^^^^^^^^^
>
> Remind me to pay you a beer! :D
>
In the DS2480 datasheet, the following is stated:
6 POL RXD/TXD Polarity Select. RXD/TXD polarity select; tied to GND for
RS232
(12V or 5V) connection; tied to VDD for direct connection to UART chip.
Sorry I lead to certain misconception with the eagle library you used (I
think). There I've written:
The RxD and TxD lines are operated at 0V/5V. The POL pin selects the
RxD and
TxD "polarity", that means straight-through or inverted. If POL is
connected
to GND, RxD and TxD behave properly for connection to inverted RS232
drivers,
like the MC1488/1489 or MAX23x chips. If POL is connected to Vdd, RxD
and TxD
behave properly for direct connection to a 0V/5V UART chip.
So the POL pin should be connected to GND if a simple
diode/transistor/resistor network is is used as the RS232 "interface", like
the Elektor schematic presumably does. If inverted drivers are used in the
peripheral, they are used on *both* sides (computer and peripheral), so the
inversion is gone and POL need to be connected to Vdd.
Hmmm. Maybe I should update the library. Could anyone of the native english
speakers here come up with an unambiguous text?
Kind regards
Jan
--
Beware of bugs in the above code;
I have only proved it correct, not tried it.
-- D. Knuth
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