Raspberry Pi Zero W + Buildroot + Pimoroni Phat DAC


#1

Hello. I have a Raspberry Pi Zero W with the Pimoroni Phat DAC.

It’s working fine on Debian Jessie, using the Pimoroni PhatDAC bash installer.
But, I’m moving on to a leaner Buildroot compiled Linux, and I just cannot get it to work there, it’s the exact same device, I’m simply swapping SD cards.

The problem is that Alsa won’t show me any sound cards in either /proc/asound or in /dev/snd.

I’m quite confused because the modules that are shown in the working Jessie linux don’t match with the Pimoroni Phat Dac guide. The working Jessie shows me that the following modules are loaded:

snd_soc_hifiberry_dac
snd_soc_bcm2835_i2s
regmap_mmio
snd_soc_pcm5102a
spi_bcm2835
bcm2835_wdt
bcm2835_gpiomem
snd_soc_core
snd_pcm_dmaengine
snd_pcm
snd_timer
snd

Not in this list are the i2c-bcm2708, snd-soc-pcm512x and snd-soc-wm8804 from the guide. I get no sound card devices when I load the same modules in the Buildroot linux or when I load the ones from the guide.

My config.txt file has:
dtparam=i2c_arm=on
dtparam=spi=on
dtoverlay=hifiberry-dac

I have not specified i2s (not in the guide, nor on the working Jessie) and dtparam=audio=on is removed.
I have not created any Alsa config files, but that shouldn’t make any difference in this case, right?
Do any of these modules need parameters? Could it be that I’m loading them to late in the boot process?

Any clues to the root cause of this problem, or any tips on things I could check?


#2

Solution: Copy hifiberry-dac.dtbo to boot/overlays
This is not done by the installer. I guess most Raspberry Pi installations have this overlay folder here, but not all.
I copied the overlays from another Raspberry Pi boot folder; I have not yet figured out the official source yet…

If anyone from Pimoroni is watching, perhaps add this to the installer, or at least a check on the presence, so you can give out a warning/instructions.