=== Adafruit Volume control ===

UPDATE: Based on a posting of user j1nx on the mycroft forum (thanks a lot!) the better way to control the initial value of the Adafruit using i2cset and an udev-rule
==== Enable I2C ====
I2C is not enabled by default so run and enable I2C in the Interfacing Options
==== Volume control with i2cset (preferred) ====
Install the i2c-tools:
* sudo apt-get install i2c-tools
The command to set the volume (30) is:
* i2cset -y 1 0x4b 30
Create the udev-rule:
* sudo nano /etc/udev/rules.d/10-i2c-sound.rules
with the content:
{{{
SUBSYSTEM=="i2c", ATTR{name}=="bcm2835 I2C adapter", RUN+="/usr/sbin/i2cset -y 1 0x4b 30"
}}}
This blindly sets the volume as soon as the i2c adapter is seen by udev.
===== How to find the value for the udev rule =====
Use the command:
* udevadm info -a -p /sys/bus/i2c/devices/i2c-1
to get the values for SUBSYSTEM and ATTR
==== Volume control with the Adafruit python library (alternative) ====
Control the volume of the MAX9744 using the CircuitPython Libraries (see [https://learn.adafruit.com/circuitpython-on-raspberrypi-linux/installing-circuitpython-on-raspberry-pi] ).
The things that I had to do: 
===== Install the library =====
while in (.venv)
* pip3 install RPI.GPIO
* pip3 install adafruit-blinka
* pip3 install adafruit-circuitpython-max9744
===== Python script =====
Use this script to set the initial volume to about the half (the range is 0 to 63). Create ~/bin/ada_volume.py with the following content
* nano ~/bin/ada_volume.py
{{{
import board
import busio
import adafruit_max9744
i2c = busio.I2C(board.SCL, board.SDA)
amp = adafruit_max9744.MAX9744(i2c)
amp.volume = 30
}}}
===== Start using systemd =====
Place a service file in the user directory:
* nano ~/.config/systemd/user/myadavolume.service
with the content
{{{
[Unit]
Description=set adafruit volume
After=network.target

[Service]
Type=simple
ExecStart=/home/pi/mycroft-core/.venv/bin/python /home/pi/bin/ada_volume.py

[Install]
WantedBy=default.target
}}}
Enable and start it:
* systemctl --user daemon-reload
* systemctl --user enable myadavolume
* systemctl --user start myadavolume

=== Pulseaudio ===
The picroft installation does not use pulseaudio for the output of voice and other sound so the general volume control did not work
==== blacklist the internal bcm2835 sound card ====
This is for sure totally optional but I did it
* sudo nano /etc/modprobe.d/alsa-blacklist.conf
{{{
blacklist snd_bcm2835
}}}
==== force ALSA userspace to use PulseAudio ====
* sudo nano /etc/asound.conf
{{{
# Use PulseAudio by default
pcm.!default {
  type pulse
  fallback "sysdefault"
  hint {
    show on
    description "Default ALSA Output (currently PulseAudio Sound Server)"
  }
}

ctl.!default {
  type pulse
  fallback "sysdefault"
}
}}}
==== mycroft conf ====
* sudo nano /etc/mycroft/mycroft.conf
replace:
{{{
   "play_wav_cmdline": "aplay -Dplughw:ArrayUAC10,0 %1",
   "play_mp3_cmdline": "mpg123 -a plughw:ArrayUAC10,0 %1",
}}}
with
{{{
   "play_wav_cmdline": "paplay %1",
   "play_mp3_cmdline": "mpg123 %1",
}}}
==== additional setting in default.pa ====
This enables ducking and is a nice feature that the volume of music playing is turned down while Mycroft speaks instead of stopping the output.
* sudo nano /etc/pulse/default.pa
add to the end of the file
{{{
unload-module module-suspend-on-idle
unload-module module-role-cork
load-module module-role-ducking
}}}