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'Q: Is there any controller with on-chip DAC?'
1996\10\05@082157 by sv

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Hello ladies & gentlemen.

I need a single-chip inexpensive sound synthesizer.
I realize that PIC (say, 16C84) + external DAC would do all,
    but they are TWO.

There are many devices with on-chip ADC, but I failed to find one with
    on-chip DAC, inexpensive and with small pin count (like PICs are).

Could somebody suggest me anything, please?
Help me to guess WHY don't they (manufacturers) integrate DAC into
    controller chips?

Thank you.
Vlasov Serge.
spam_OUTsvTakeThisOuTspamiae.nsk.su

1996\10\06@204001 by Larry G. Nelson Sr.

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At 08:21 AM 10/5/96 -0400, Vlasov Serge V. wrote:
>Hello ladies & gentlemen.
>
>I need a single-chip inexpensive sound synthesizer.
>I realize that PIC (say, 16C84) + external DAC would do all,
>     but they are TWO.
>
>There are many devices with on-chip ADC, but I failed to find one with
>     on-chip DAC, inexpensive and with small pin count (like PICs are).
>
>Could somebody suggest me anything, please?
>Help me to guess WHY don't they (manufacturers) integrate DAC into
>     controller chips?
>
>Thank you.
>Vlasov Serge.
>.....svKILLspamspam@spam@iae.nsk.su
>
>
How about PWM to an RC to generate a DAC output. Quality will not be great
but may be "Good Enough"
Larry G. Nelson Sr.
L.NelsonspamKILLspamieee.org
http://www.ultranet.com/~nr

1996\10\07@214152 by Steve Hardy

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> From: "Vlasov Serge V." <.....svKILLspamspam.....IAE.NSK.SU>
>
> Hello ladies & gentlemen.
>
> I need a single-chip inexpensive sound synthesizer.
> I realize that PIC (say, 16C84) + external DAC would do all,
>      but they are TWO.
>
> There are many devices with on-chip ADC, but I failed to find one with
>      on-chip DAC, inexpensive and with small pin count (like PICs are).
>
> Could somebody suggest me anything, please?
> Help me to guess WHY don't they (manufacturers) integrate DAC into
>      controller chips?

Well, they do.  The PIC16C73/74 has an on-board PWM which is a form of
DAC.  The PIC PWM has a resolution of up to 10 bits, depending on the
highest desired carrier frequency.

Getting a DAC function is the easy bit.  The hard bit is generating
a useful waveform to send to it.  Square, triangle, saw-tooth and sine
waves are easy enough.  For a synthesiser you will need attack/decay/
sustain/release control.  This implies a multiplication operation in the
digital domain: not all that easy using a PIC without hardware multiply.
It can be done, but your output frequency may be limited to a few hundred
Hertz.

Regards,
SJH
Canberra, Australia

1996\10\08@005426 by John Payson

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> Getting a DAC function is the easy bit.  The hard bit is generating
> a useful waveform to send to it.  Square, triangle, saw-tooth and sine
> waves are easy enough.  For a synthesiser you will need attack/decay/
> sustain/release control.  This implies a multiplication operation in the
> digital domain: not all that easy using a PIC without hardware multiply.
> It can be done, but your output frequency may be limited to a few hundred
> Hertz.

Actually, if you have a **REAL** DAC (as opposed to a PWM) there are some
nifty tricks that can be used for envelope generation.  For example, you
can time-domain-multiplex several source signals, varying the amount of
time each signal is output to adjust its strength (during any time left
over once all signals have been output should be tri-stated).  Using this
and a couple other super-secret [:-)] tricks I've managed to produce a
music box which generates 8 simultaneous (sinewave) tones with independent
logarithmic decay, at an output rate of one full set of samples every 256
cycles [about 10KHz on a 16C84].  A true built-in DAC would have made the
process a bit easier (though 16 resistors isn't too bad) and I want to put
in a 20MHz 16C620 to up the output sampling rate (maybe save a stage of
filtering and improve frequency response).

In short, the PIC's instruction set is very definitely powerful enough for
audio.

1996\10\08@094550 by Martin J. Maney
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On Mon, 7 Oct 1996, John Payson wrote:
> Actually, if you have a **REAL** DAC (as opposed to a PWM) there are some
> nifty tricks that can be used for envelope generation.  For example, you
> can time-domain-multiplex several source signals, varying the amount of
> time each signal is output to adjust its strength (during any time left

Or, at the cost of a bit more hardware, you can output the envelope,
sample it, and then use it as the reference input to the "multiplying"
DAC for the waveform sample.  A little more hardware, but it uses less
CPU cycles for manipulating the DAC & etc.

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