X9C103S Digital volume control (potentiometer)

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Zim
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X9C103S Digital volume control (potentiometer)

Post by Zim »

Hi
Has anyone ever implemented this with Annex? Is it possible. Sure would be useful! I would like to replace the pot in a small amp for my home audio and control it from annex using a infra red remote.

Thanks
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PeterN
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Re: X9C103S Digital volume control (potentiometer)

Post by PeterN »

Hello Zim

This seems to be a very interesting IC.
The datasheet says that it is a LINEAR potentiometer with an up/down controllable 100 step wiper.
https://www.renesas.com/en/document/dst ... -datasheet

I think this is easy to control via Annex and three output pins for chip select, UP/down select, increment step pulses
For the replacement of a volume potentiometer, there should only be the electrical constraint that the potentiometer pins remain within plus minus 5V relative to ground.
The ICs Vcc is 5V but the inputs will accept 3V3 level as high signal level.
Another point to note is that a hardware volume potentiometer usually has a logarithmic curve - it could be an interesting part of the software to emulate this characteristic curve with Annex
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Re: X9C103S Digital volume control (potentiometer)

Post by bugs »

It may depend on how critical you are with the audio.
I have not used that particular digital potentiometer but did have occasion to prototype a couple of DS1666 (now obsolete) 256 step audio taper devices for a customer of a company I contracted for. The problem is/was "zipper noise". If there is no audio signal then no problem changing the pot position but with any voltage (DC or signal) across the pot, the step noise can be noticeable.
I did use them at home to enable remote volume control and was not bothered too much with the slight noise.
I dug out the module from a drawer and found that I had used a PIC which probably means it was 20+ years ago!
So no circuit or program.
Anyway - try a web search for zipper noise and potentiometer and see what you think...
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Re: X9C103S Digital volume control (potentiometer)

Post by PeterN »

Hi Bugs,

that stepping behavior is interesting.
Did you do a calculation to map the linear control value to an exponential wiper position , to emulate a „real“ volume pot?

EDIT: Just saw that your device already has a pseudo-logarithmic resistor array
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Re: X9C103S Digital volume control (potentiometer)

Post by BeanieBots »

A little late to the party but there is a very simple trick to make a linear pot 'look' (almost) logarithmic.
Simply add a resistor between the wiper and 0v.
The resistor value should be ~1/2 the pot value.
Software could be an option but I fear that with only 100 steps, resolution would be further reduced.
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