Getting the audio injector working with Buildroot embedded!

[jessecobra]

I love the Raspberry Pi Zero W, but I dislike how long it takes to boot using the Raspbian image. 10-30 seconds!

So I went down the path of getting Buildroot working on my Raspberry Pi Zero W and then the Audio Injector sound card.
Buildroot boots on the Zero W in 3 seconds!

Audio works in seconds!

If anyone else wants to try this here is the tutorial I am following: http://www.jumpnowtek.com/rpi/Raspberry ... droot.html
I noticed flatmax had some issues here that I did not run into: https://www.raspberrypi.org/forums/view ... &p=1263867

Here are some of the changes to Buildroot [master] in his [jumpnow] branch that all worked for me.
- Newer versions of the Linux kernel and RPi firmware
- Some custom applications primarily as an experiment in how to add custom packages to Buildroot. The source for all of them are public github repos.
- serialecho - a C, Makefile based app
- tspress - a Qt5 Widgets GUI app using qmake
- pytouch.py - a PyQt5 app
- Custom Buildroot defconfigs to support my images for the RPi boards.
- Sample rootfs overlays to customize conf files. <- This is the important one!

Some patches to the kernel build so that the RPi DTS overlays (DTBOs) are built from the kernel source and not just downloaded from the RPi firmware github repo. This make its a little easier (at least for my workflow) to include custom dts overlays when you need them by just including them as kernel patches.

So lets get started:

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git clone -b jumpnow https://github.com/jumpnow/buildroot
cd buildroot
make jumpnow_rpi0_defconfig
make

It will take a few hours to build the whole system then you image an SD card with the resulting image:

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sudo dd if=output/images/rpi0-sdcard.img of=/dev/sdb bs=1M

After testing this image I added alsa-lib and a few of the alsa test apps:

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make menuconfig 

Add alsa-lib and whatever alsa apps you need in this config.

Also I added PREEMPT support to the kernel:

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made linux-menuconfig

Of course go edit your /boot/config.txt

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sudo nano /boot/config.txt
add: dtoverlay=audioinjector-wm8731-audio

Reboot and you are done!

Oh yea! don't forget to load the alsa settings from the audio injector deb.tar.gz file in the setup thread:

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alsactl --file asound.state.RCA.thru.test restore
amixer sset 'Master' 121
amixer sset 'Capture' 23
alsactl store

I need to do this at every boot, I just added it to an /etc/init.d/S60_audiosetup.sh script!

[riedlse]

Thank You !!!, just the post I was looking for...

[flatmax]

I just compiled and this works nicely !

[wh7qq]

Does this work on other RPi models, like the 2B? I should have left well enough alone and had a working stereo card on Jessie but when I upgraded to Stretch, it no longer works at all.

[wh7qq]

I stumbled early at

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make jumpnow_rpi0_defconfig

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conf.c:6:10: fatal error: locale.h: No such file or directory
 #include <locale.h>

I am not into C code and don't know where to get this or where it should live when obtained. Any help?

[wh7qq]

I managed to build a functional image...boots to a command prompt and does some commands...but now I am all dressed up with no place to go...how to find/install applications? I recommend using copy/paste on the commands...memory or finger failures lead to build errors.

For anyone contemplating this, the buildroot process will use about 2.5 Gig if you are on a metered connection (as I am). The saving in boot time may not be worth the build time plus the acquisition of applications.