On Thursday, Nov 27, 2003, at 02:50 US/Pacific,
egnascimento@YAHOO.COM.BR wrote:

> It is impossible.

That seems unlikely.  See below...

> Try to use a LM386 between the PIC and the speaker!

An actual audio amplifier IC is surely overkill for a digital square
wave.
At worst, you can get by with a transistor.
You can almost certainly get by with a resistor that limits current to
the maximum that the pic pin is supposed to deliver (assume 0 ohms DC
resistance for the speaker and you'll be safe.)

It does bring up an interesting question, though.  To what extent IS it
safe to drive a 0-ohm load from a PIC pin?  On the one hand, you have
those maximum current output specs (25mA) from the datasheet.  On the
other hand, you have the internal circuitry, which being cmos likely
provides some sort of inherent current limiting, and perhaps some sort
of intentional short-circuit protection in the I/O circuitry as well.
Not to mention loads of circuits that apparently work OK that connect
everything from LEDs to speakers directly between IO pins and power
supply without any additional current limiting...

BillW

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