Re: A89: >1-bit sound on the 89
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Re: A89: >1-bit sound on the 89
On Sat, Apr 15, 2000 at 11:35:05AM -0700, Seth Peelle wrote:
>
> Forgive me for my lack of calc hardware knowledge... I understand that
> link port 1-bit sound is created by rapidly switching the link on and
> off (correct me if I'm wrong). Are there any possible methods for
> making sound with greater bit-depth (i.e. 2-bit, 4-bit, 8-bit, etc.)?
> That would create some interesting potential for sound/music synthesis.
Well... One could put some microcontroller as a gateway between TI89 and DAC
(DAC is a hardware chip which converts digital signals to voltage levels
which could be then amplified and feed to a headphone or ... speaker (I
remembered the word!!! :)). That would need much hardware to do the job, but
then... if the microcontroller was programmed to do some synthesis, it would
be quite a good way to produce music, as the TI89 wouldn't need to do more
than to output the correct notes, lengths, and waveforms to the controller.
(Samples need too much space to be stored even on TI89, yes it is possible,
but the length is minimal, decompression eats calculating power, and quality
is terrible).
Other way, which could also be used, is to output variable length pulses to
the link port. Then if the overall pulse frequency is high enough, and if it
was filtered away, then the variable length pulses would end up being (on
average) different voltage levels. They could then be pulsed to generate the
sound.
For example, if there was four different lengths of pulse: 1/4 2/4 3/4 4/4
Then 1/4 would be "one fourth signal level" etc.. so this would be 2bit
sound. There is major drawbacks in this (PWM Pulse Width Modulation) scheme.
There is the pulsing frequency for the variable length pulses which could be
heard on the background noise for the inteded sound. And it takes quite a
lot of CPU cycles to generate the variable length pulses.
Well, on the above explanation the variable length pulse means that the
overall width of the "pulse" is fixed, but the amount of time the pulse is
high, i.e. "1", i.e. 5V, is variable.
I'm really sorry for the poor explanation, but as English is not my native
language... I really can't explain things very well. Maybe someone will
clarify/correct my explanation.
> On a side note, and out of sheer curiosity, is there any reason in
> particular why a disproportionate amount of TI calc programmers are
> French? Not trying to discriminate or anything, just simply wondering
> :)
That is mystery for me too... I've been wondering why there aren't any other
Finns on the TI89 scene... :-) Am I alone in the big world? 8-]
Henri Moilanen
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