Simple RS232 hardware
There is no such thing as an official specification for a PC.
If you want to be really picky, the standard PC itself doesn't
correspond to the RS232 spec (or is it V24 - can't remember what bits
are specified where). as the gender of the connector is wrong.
In practice, using 5V levels works, and I have enough units in the
field running on all shapes and sizes of PC to be confident that if
there are any odd PCs out there that don't work they are an
insignificant minority that I needn't worry about. Where there is the space and budget for transceivers, fine - use them
and sleep more soundly - I've designed them into several products,
where appropriate. However for applications which are very price
and/or space limited, fitting unnecessary components is wasteful.
There is another important aspect to this - for serial devices that
are RS232-powered (e.g. little custom interface devices which live in
a D9 connector shell), you need to get the power consumption as low as
possible to avoid teh risk of power dropout problems - using 5v levels
without a transceiver saves power. I am WAY more worried about
problems due to insufficient power availability (especially on laptops
etc.) than marginal signal levels. This is why I always use a
micropower LDO instead of a 78L05 in production devices.
On Mon, 10 Sep 2001 07:35:16 -0400, you wrote:
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In reply to: <003f01c139ec$a9e58160$220bf6cd@main>
See also: www.piclist.com/techref/microchip/ios.htm?key=rs232
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