Plug and play software / hardware volume control for piano 2.1 DAC?

[Doron Behar]

So, today I run `amixer -c0` on my Raspberry Pi with Piano 2.1 DAC + Kali reclocker, and I saw this:
 

Simple mixer control 'Volume Ramp Down Rate',0
  Capabilities: enum
  Items: '1 sample/update' '2 samples/update' '4 samples/update' 'Immediate'
  Item0: '1 sample/update'
Simple mixer control 'Volume Ramp Down Step',0
  Capabilities: enum
  Items: '4dB/step' '2dB/step' '1dB/step' '0.5dB/step'
  Item0: '1dB/step'
Simple mixer control 'Volume Ramp Up Rate',0
  Capabilities: enum
  Items: '1 sample/update' '2 samples/update' '4 samples/update' 'Immediate'
  Item0: '1 sample/update'
Simple mixer control 'Volume Ramp Up Step',0
  Capabilities: enum
  Items: '4dB/step' '2dB/step' '1dB/step' '0.5dB/step'
  Item0: '1dB/step'

 
Which suggests that the hardware supports some kind of plug and play volume control that controls directly the card? Perhaps this feature is available via the spare GPIO pins?

 

P.S I wanted to post this question on allo's forum, but the website wouldn't let me do it from some reason.

[stefano_mbp]

Volumio should give hardware volume control functionality 

[bluesman]

You can add hard controls for volume onto GPIO pins.  Use GPIOzero to configure the pins for physical switching.  Here’s a link to introduce you to gpiozero.  Here’s a link to the documentation for using it.  You should also be familiar with the pigpio library, another Python library for such use.

[Doron Behar]

Thanks for the links @bluesman. I'm familiar with the concept of GPIO pins in Raspberry Pi. I don't understand something else: Here's what the datasheet for the Piano DAC is saying:

 

 

So I guess I can go ahead and connect anything I want to pins 6,8,10,14,13? But pin 13 and 14 seem to be of special purpose - labeled SDZ_AMP and MUTE_AMP . Are pins 13 & 14 ready to be used directly, without software to setup? Is this what's counted as true "hardware volume control"? I'm pretty sure that connecting encoders to the other GPIO pins and writing a software daemon that will run `amixer` commands would not be considered a hardware based volume control.

 

P.S I don't use volumio - I'm trying to setup it up all by myself.

[bluesman]

I don’t have that hardware,so I haven’t done this myself & can’t confirm for you. Today’s a holiday for me, so I’ll look into it on Monday & let you know. Stay safe!