<div dir="ltr">Hi,<div>In my 6 years old VCO Module (AetherOscillator) I use the <span style="font-size:12.8px">dsPIC33FJ128GP802 but with a external DAC.</span></div><div><span style="font-size:12.8px">I had many problems with the internal DAC and the maximum sample rate is 100KHz. </span></div><div><span style="font-size:12.8px"><br></span></div><div><span style="font-size:12.8px"><a href="http://www.vbrazilsystems.com/aether-oscillator.html">http://www.vbrazilsystems.com/aether-oscillator.html</a></span><br></div><div><span style="font-size:12.8px"><br></span></div><div><span style="font-size:12.8px">Some demos & tests involving Aether Oscillator:</span></div><div><span style="font-size:12.8px"><br></span></div><div><span style="font-size:12.8px"><a href="https://soundcloud.com/vinicius-brazil/as1-demo34-crossfm2">https://soundcloud.com/vinicius-brazil/as1-demo34-crossfm2</a></span><br></div><div><span style="font-size:12.8px"><a href="https://soundcloud.com/vinicius-brazil/as1-demo28-sequencia-semi">https://soundcloud.com/vinicius-brazil/as1-demo28-sequencia-semi</a></span><br></div><div><span style="font-size:12.8px"><a href="https://soundcloud.com/vinicius-brazil/as1-demo27-acusticbass">https://soundcloud.com/vinicius-brazil/as1-demo27-acusticbass</a></span><br></div><div><span style="font-size:12.8px"><a href="https://soundcloud.com/vinicius-brazil/as1-demo9-aetheroscillators">https://soundcloud.com/vinicius-brazil/as1-demo9-aetheroscillators</a></span><br></div><div><span style="font-size:12.8px"><a href="https://soundcloud.com/vinicius-brazil/as1-demo3-assobio">https://soundcloud.com/vinicius-brazil/as1-demo3-assobio</a></span><br></div><div><span style="font-size:12.8px"><a href="https://soundcloud.com/vinicius-brazil/as1-demo6-sequencia1">https://soundcloud.com/vinicius-brazil/as1-demo6-sequencia1</a></span><br></div><div><span style="font-size:12.8px"><a href="https://soundcloud.com/vinicius-brazil/as1-demo7-sequencia2">https://soundcloud.com/vinicius-brazil/as1-demo7-sequencia2</a></span><br></div><div><span style="font-size:12.8px"><br></span></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jun 14, 2016 at 3:39 PM, <span dir="ltr"><<a href="mailto:sleepy_dog@gmx.de" target="_blank">sleepy_dog@gmx.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div><br>
Square wave on the DAC?<br>
<br>
Would it not be enough to just do that with a harwdare PWM
channel?<br>
It did sound nice enough at first "glance" when I tried it, but
I'm not sitting on a pile of signal theory to know what I'm doing
there ^^<br>
I mean including PWM. I.e. directly using a PWM timer output
swinging at the pitch you want to play, LFO-modulated in the
firmware - sure, the PW resolution varies depending on pitch, but
it sounded nice enough to me. Between the low end and 7 kHz. I
have not looked at the spectrum or would know how that of a
typical synth pwm should look like, though.<br>
<br>
But if you could do that, then you'd have 3 waveforms on the dac,
plus PW-variable square.<br>
<br>
Is the F303 + needed parts & PCB still cheaper than the other
options, though? (I have no idea what the old chips cost)<br>
<br>
Steve<div><div class="h5"><br>
<br>
<br>
Am 14.06.2016 um 20:00 schrieb Vladimir Pantelic:<br>
</div></div></div><div><div class="h5">
<blockquote type="cite">
<p dir="ltr">STM32F303 has 3 12-bit DACs and a ton of 12 bit ADC
channels. so saw, square, triangle and sine via an external
shaper for extra grit :)<br>
</p>
<p dir="ltr">On Jun 14, 2016 7:54 PM, "Tim Ressel" <<a href="mailto:timr@circuitabbey.com" target="_blank"></a><a href="mailto:timr@circuitabbey.com" target="_blank">timr@circuitabbey.com</a>>
wrote:<br>
><br>
> Two DAC output yields 2 waveforms. I'm thinking sine and
triangle. A digital out pin can make squares and PWMs, or a
comparator can handle it. If you make triangles rather than
sawtooths then the DAC holds together better at higher
frequencies. It is a simple matter of converting a tri to a saw
externally.<br>
><br>
> I don't see 12 bit ADCs as much of a limitation. It should
do V/Oct out to 10 octaves.<br>
><br>
> --TimR<br>
><br>
><br>
> On 6/14/2016 10:40 AM, Tom Wiltshire wrote:<br>
>><br>
>> On 14 Jun 2016, at 16:44, Tim Ressel <<a href="mailto:timr@circuitabbey.com" target="_blank"></a><a href="mailto:timr@circuitabbey.com" target="_blank">timr@circuitabbey.com</a>>
wrote:<br>
>><br>
>>> Speaking of doable, it should be possible to take a
DSP chip and mimic the function of a 3340. Yes I know, the 3340
has "that sound". But it also has "that price". I'm thinking the
DSPIC33FJ128GP802. It comes in a 28 pin dip and has built-in
audio DACs. Might be interesting.<br>
>><br>
>><br>
>> The idea had occurred to me too, for the same reasons -
the dsPIC 33FJ128GP802 is about the right size and format to
make a good analog oscillator substitute. It has two DAC
channels, so maybe even a dual oscillator would be possible.<br>
>><br>
>> There are definitely limitations with the chip (only
six 12-bit ADC inputs when using the DAC, for example), and
moving to a digital chip implies doing certain things
differently (you won't get multiple waveform outputs in
parallel, for instance). It's a good idea, and one I've played
with quite often, but never been happy enough with the result.
That won't stop me trying again though.<br>
>><br>
>> In some ways, I think it might make more sense to go in
the direction of my 8-bit PIC VCDO and give up with pure virtual
analog and accept that you can do a better job if you don't try
and be something you're not. Perhaps it should be a
voltage-controlled digital oscillator chip, doing a few of the
interesting things you can do digitally instead of trying to do
anti-aliased analog waveforms with hard sync and PWM and so
forth.<br>
>><br>
>> Tom<br>
>><br>
>><br>
>><br>
><br>
> -- <br>
> --Tim Ressel<br>
> Circuit Abbey<br>
> <a href="mailto:timr@circuitabbey.com" target="_blank">timr@circuitabbey.com</a><br>
><br>
><br>
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