Re: Apple II Speaker

["M. Pender" <mpender@hotmail.com>]

Bill Garber <willy46pa@comcast.net> wrote in message
oJWdnTSVzej4mlqiRVn-tA@comcast.com">news:oJWdnTSVzej4mlqiRVn-tA@comcast.com...
>
> Is there a place I can read the numeric
> values of the signals being sent to the
> A2 speaker? I know that it is being fed
> pulses at different speeds to create the
> pitch, but I need to be able to distinguish
> one tone from another for a program I want
> to write. If I find this info before I get
> replies I will post as such.

IIRC the A2 speaker is connected to a toggle that is flipped by either
reading or writing to a softswitch ($c030?), so any attempt to read that
memory location would result in additional toggling of the switch.  Again,
IIRC a write to the switch toggles it once and a read to the switch does a
double-toggle.

One approach would be to attach a diode and RC circuit to the speaker output
and determine the frequency indirectly.  The voltage across the capacitor
would vary according to the toggle rate of the speaker.

That said, I think tones are generated using a system function and the tone
parameters could be read without directly affecting the speaker.  I expect a
similar system function also exists for the IIgs ensoniq chip.

Can you tell us a little more about the project?

- Mike