Daisy 16 Audio adapter

FoxBoard G20 Audio Support Preview

On this page you can find all the information about the development to add audio support
to Foxboard using the new Daisy cabling system.
The audio codec used is the WM8731, is low power stereo codecs with an integrated headphone driver, stereo line-out, stereo line-in and mono microphone level audio inputs.

WM8731 Codecs is supported by the Linux kernel and works with alsa drivers.

Schematics daisy_16_audio.pdf

Dimension: 40x40mm

• Stereo 24-bit multi-bit sigma delta ADCs and DACs are used with oversampling digital interpolation and decimation filters.
• Highly Efficient Headphone Driver
• Audio Performance : ADC SNR 90dB at 3.3V , DAC SNR 100dB at 3.3V
• Low Power : Playback only 22mW
• Selectable ADC High Pass Filter
• Microphone Input and Electret Bias with Side Tone Mixer

The communication between the FoxBoard and the Codecs is done by SSC (Synchronous Serial Controller) for the audio interface (Daisy D5 ←→ J2)
and I²C for control interface (Daisy D6 ←→ J1).

WM8731 codecs is supported in the linux kernel but to be used with the daisy16 needs some changes. You must apply an additional patch.

these kernels contain the default acmesystems configuration with Daisy16 Support

Files to store in the first FAT16 partition:

• Kernel 2.6.35.4 image daisy16_2.6.35.4_uImage (MD5:daf39e532a84e1a29f764efbe31a4e05)
• Kernel 2.6.38 image daisy16_2.6.38_uImage (MD5:74ba68dd909db3edb2ab73bff9707250)

Linux kernel 2.6.35.4

• Download the kernel sources and apply Acme Systems patch:
  

  $ wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.35.4.tar.bz2
  $ tar -xjvf linux-2.6.35.4.tar.bz2
  $ cd linux-2.6.35.4
  $ wget http://www.acmesystems.it/foxg20/download/kernel/0003-Acme-Systems-board-files.patch
  $ patch -p1 < 0003-Acme-Systems-board-files.patch
  $ wget http://www.acmesystems.it/foxg20/download/kernel/makefile

• Download the Madefree Patch
  daisy16_26354.tar.gz (MD5:8e5ede6d218e34574c71cfdbcb880dfc)
• Apply the patch:
  

  $ tar -xzvf daisy16_26354.tar.gz
  $ patch -p1 < daisy16_26354/daisy16_26354.patch

• Then copy the .config to use the last Madefree factory default configuration files:
  

  $ cp daisy16_26354/daisy16_26354.config .config

• Configuring your kernel:
  

  $ make menuconfig

• Building your kernel:
  

  $ make

Linux kernel 2.6.38

• Download the kernel sources :
  

  $ wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.38.tar.bz2
  $ tar -xjvf linux-2.6.38.tar.bz2
  $ cd linux-2.6.38
  $ wget http://foxg20.acmesystems.it/download/kernel_2.6.38/makefile

• Download the Madefree Patch
  daisy16_2638.tar.gz (MD5:c9f75aca53b6858c3c82edd5a497b718)
• Apply the patch:
  

  $ tar -xzvf daisy16_2638.tar.gz
  $ patch -p1 < daisy16_2638/daisy16_2638.patch

• Then copy the .config to use the last Madefree factory default configuration files:
  

  $ cp daisy16_2638/daisy16_2638.config .config

• Configuring your kernel:
  

  $ make menuconfig

• Building your kernel:
  

  $ make

• Check dmesg after boot:
  

  ...
  ssc ssc.0: Atmel SSC device at 0xc48a0000 (irq 14)
  ...
  netusG20_wm8731 : daisy16: wm8731__init() called
  asoc: wm8731-hifi <-> atmel-ssc-dai.0 mapping ok
  ALSA device list:
    #0: DAISY16
  ...
  

• Install alsa-utils
  

  apt-get install alsa-utils

• Run alsamixer:
  

  alsamixer -V all

• Configure ALSA like this
  
• Launch recording for 5sec. stereo wav acquisition
  

  arecord -d 5 -v -v -Dhw:0,0 -f cd record_line_in.wav

• Play what you recorded
  

  aplay record_line_in.wav

A great console music player is cmus

apt-get install cmus
cmus

Cmus has a syntax very similar to vim:

:add 'directory_audio'  # add audio file to playlist
:q  # exit to cmus
z  # previous
x  # play
c  # pause
v  # stop
b  # next
^L # refresh
n  # search-next
r  # toggle repeat
1  # view tree
2  # view sorted
3  # view playlist
4  # view queue
5  # view browser
6  # view filters
7  # view settings
+  # vol +10%
-  # vol -10%

Fox G20 Website
WM8731 Datasheet
Madefree Electronics Shop