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 Forum index » DIY Hardware and Software » Microcontrollers and Programmable Logic
Generate CV signal - PWM or DAC?
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greg



Joined: Nov 13, 2006
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PostPosted: Thu Apr 09, 2020 12:47 am    Post subject: Generate CV signal - PWM or DAC? Reply with quote  Mark this post and the followings unread

I need at least 8 control voltage sources in the range of 0V-10V, DC and AC (sub audio range). I am using a Cortex M4 microcontroller (ST32) and wonder what would be the easiest solution:

- external audio codec IC with I2C or I2S or SPI
- external PWM IC with 1-bit DACs built from discreet components
- FPGA/CPLD with PWM outs and 1-bit DACs built from discreet components

Anyone has experience generating CV digitally?
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JovianPyx



Joined: Nov 20, 2007
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PostPosted: Thu Apr 09, 2020 5:15 am    Post subject: Reply with quote  Mark this post and the followings unread

I've used AD5676 to generate both CV and audio. 8 channels of output, so sample and holds not needed.
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Electric Druid



Joined: Mar 13, 2012
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PostPosted: Wed Jul 22, 2020 1:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

You say "DC/ AC sub-audio" so I don't see why a audio codec is a proposed solution. You may well find an audio codec would have highpass filters making sending DC out of it impossible. An 8-channel audio codec might be more expensive than you want.

PWM can work, but it's pretty noisy unless the filtering is good and/or the bandwidth required is low and/or the required resolution is low. Not recommended, unless you're going for super-simple.

FPGA/CPLD seems like massive overkill. Reinventing the wheel using a supercomputer much?!? Wink Why? This is a solved problem. Don't solve it again.

Ultimately, like Scott said, the best bet would be multi-channel DACs of some type. You choose I2C or SPI depending on what you like best or have available.

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Grumble



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PostPosted: Wed Jul 22, 2020 2:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

You can use single multiplying dac’s in chain spi mode.
This way you have an easy envelope control as bonus.
Always use (hardware) spi, thats the fastest.

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