[sdiy] Trueno

Vladimir Pantelic vladoman at gmail.com
Wed Dec 13 15:58:02 CET 2017


On 13.12.2017 10:30, Roman Sowa wrote:
> Here are more detailed pictures:
> http://www.synthdiy.eu/files/truenobottom.jpg
> http://www.synthdiy.eu/files/truenobottom2.jpg
> http://www.synthdiy.eu/files/truenobottom3.jpg
> http://www.synthdiy.eu/files/truenotop.jpg
> http://www.synthdiy.eu/files/truenotop2.jpg
> http://www.synthdiy.eu/files/truenotop3.jpg
> 
> You were right, Neil, that's pair of LM4250 in the filter.
> Also on the bottom side:
> 3rd VCO that was missing from yesterday's picture, with inevitable Kynar
> job, STM32F042C6 for the brains, ADC - AKM5720, and silkscreen suggests
> analog part works at +/-3.5V supply.

so now, where do the CVs for the VCOs come from? the STM32042 has no
DACs and I see no external DAC either, so the CVs are all lowpass'd PWM
from the STM?

or - and that could explain the aliasing seen in the signals - the STM32
itself provides the saw ramp reset timing signals and there is only a
coarse CV for the current source to charge the timing caps?



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