Enable basic audio support

README.md

@@ -30,6 +30,7 @@ appropriate for your setup.
 | Ethernet             | Yes - via OTG USB port          |
 | WiFi                 | Supported on the Pi Zero W      |
 | Bluetooth            | Not supported yet               |
+| Audio                | HDMI/Stereo out                 |
 
 ## Using
 
@@ -79,6 +80,28 @@ The base image includes drivers for the onboard Raspberry Pi Zero W wifi module
 (`brcmfmac` driver). Due to the USB port being placed in gadget mode, this
 system does not support USB WiFi adapters.
 
+## Audio
+
+The Raspberry Pi has many options for audio output. This system supports the
+HDMI and stereo audio jack output. The Linux ALSA drivers are used for audio
+output.
+
+To try it out, run:
+
+```elixir
+:os.cmd('espeak -ven+f5 -k5 -w /tmp/out.wav Hello')
+:os.cmd('aplay -q /tmp/out.wav')
+```
+
+The general Raspberry Pi audio documentation mostly applies to Nerves. For
+example, to force audio out the HDMI port, run:
+
+```elixir
+:os.cmd('amixer cset numid=3 2')
+```
+
+Change the last argument to `amixer` to `1` to output to the stereo output jack.
+
 ## Provisioning devices
 
 This system supports storing provisioning information in a small key-value store

config.txt

@@ -5,6 +5,7 @@
 #
 # Useful links:
 # https://www.raspberrypi.org/documentation/configuration/config-txt/README.md
+# https://www.raspberrypi.org/documentation/configuration/device-tree.md
 # https://github.com/raspberrypi/documentation/blob/master/configuration/device-tree.md
 
 kernel=zImage
@@ -17,8 +18,10 @@ disable_splash=1
 # configuration. See Target packages->Hardware handling->Firmware.
 gpu_mem=192
 
-# Enable I2C and SPI
-dtparam=i2c_arm=on,spi=on
+# Enable I2C, SPI, and audio
+dtparam=i2c_arm=on
+dtparam=spi=on
+dtparam=audio=on
 
 # Comment this in or modify to enable OneWire
 # NOTE: check that the overlay that you specify is in the boot partition or

linux-4.14.defconfig

@@ -9,7 +9,6 @@ CONFIG_BLK_CGROUP=y
 CONFIG_RT_GROUP_SCHED=y
 CONFIG_CGROUP_PIDS=y
 CONFIG_CGROUP_FREEZER=y
-CONFIG_CPUSETS=y
 CONFIG_CGROUP_DEVICE=y
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_NAMESPACES=y
@@ -208,44 +207,12 @@ CONFIG_LOGO=y
 # CONFIG_LOGO_LINUX_VGA16 is not set
 CONFIG_SOUND=y
 CONFIG_SND=m
-CONFIG_SND_HRTIMER=m
+# CONFIG_SND_SUPPORT_OLD_API is not set
 CONFIG_SND_SEQUENCER=m
-CONFIG_SND_SEQ_DUMMY=m
-CONFIG_SND_DUMMY=m
 CONFIG_SND_ALOOP=m
-CONFIG_SND_VIRMIDI=m
-CONFIG_SND_MTPAV=m
-CONFIG_SND_MPU401=m
 CONFIG_SND_SOC=m
 CONFIG_SND_BCM2835_SOC_I2S=m
 CONFIG_SND_BCM2708_SOC_GOOGLEVOICEHAT_SOUNDCARD=m
-CONFIG_SND_BCM2708_SOC_HIFIBERRY_DAC=m
-CONFIG_SND_BCM2708_SOC_HIFIBERRY_DACPLUS=m
-CONFIG_SND_BCM2708_SOC_HIFIBERRY_DIGI=m
-CONFIG_SND_BCM2708_SOC_HIFIBERRY_AMP=m
-CONFIG_SND_BCM2708_SOC_RPI_DAC=m
-CONFIG_SND_BCM2708_SOC_RPI_PROTO=m
-CONFIG_SND_BCM2708_SOC_JUSTBOOM_DAC=m
-CONFIG_SND_BCM2708_SOC_JUSTBOOM_DIGI=m
-CONFIG_SND_BCM2708_SOC_IQAUDIO_DAC=m
-CONFIG_SND_BCM2708_SOC_IQAUDIO_DIGI=m
-CONFIG_SND_BCM2708_SOC_ADAU1977_ADC=m
-CONFIG_SND_AUDIOINJECTOR_PI_SOUNDCARD=m
-CONFIG_SND_AUDIOINJECTOR_OCTO_SOUNDCARD=m
-CONFIG_SND_DIGIDAC1_SOUNDCARD=m
-CONFIG_SND_BCM2708_SOC_DIONAUDIO_LOCO=m
-CONFIG_SND_BCM2708_SOC_DIONAUDIO_LOCO_V2=m
-CONFIG_SND_BCM2708_SOC_ALLO_PIANO_DAC=m
-CONFIG_SND_BCM2708_SOC_ALLO_PIANO_DAC_PLUS=m
-CONFIG_SND_BCM2708_SOC_ALLO_BOSS_DAC=m
-CONFIG_SND_BCM2708_SOC_ALLO_DIGIONE=m
-CONFIG_SND_BCM2708_SOC_FE_PI_AUDIO=m
-CONFIG_SND_PISOUND=m
-CONFIG_SND_SOC_ADAU1701=m
-CONFIG_SND_SOC_ADAU7002=m
-CONFIG_SND_SOC_AK4554=m
-CONFIG_SND_SOC_SPDIF=m
-CONFIG_SND_SOC_WM8804_I2C=m
 CONFIG_SND_SIMPLE_CARD=m
 # CONFIG_HID_GENERIC is not set
 CONFIG_USB_DWC2=y

nerves_defconfig

@@ -29,13 +29,23 @@ BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="bcm2708-rpi-0-w bcm2708-rpi-b-plus"
 BR2_LINUX_KERNEL_EXT_KERNEL_WIRELESS_REGDB=y
 BR2_PACKAGE_BUSYBOX_CONFIG="${BR2_EXTERNAL_NERVES_PATH}/board/nerves-common/busybox-1.22.config"
+BR2_PACKAGE_ALSA_UTILS=y
+# BR2_PACKAGE_ALSA_UTILS_ALSAMIXER is not set
+BR2_PACKAGE_ALSA_UTILS_AMIXER=y
+BR2_PACKAGE_ALSA_UTILS_APLAY=y
+BR2_PACKAGE_ESPEAK=y
 BR2_PACKAGE_E2FSPROGS=y
 # BR2_PACKAGE_E2FSPROGS_FSCK is not set
 BR2_PACKAGE_RPI_FIRMWARE=y
 BR2_PACKAGE_RPI_FIRMWARE_KERNEL_4_14=y
 BR2_PACKAGE_RPI_FIRMWARE_X=y
 BR2_PACKAGE_RPI_WIFI_FIRMWARE=y
 BR2_PACKAGE_RPI_USERLAND=y
+# BR2_PACKAGE_ALSA_LIB_RAWMIDI is not set
+# BR2_PACKAGE_ALSA_LIB_HWDEP is not set
+# BR2_PACKAGE_ALSA_LIB_SEQ is not set
+# BR2_PACKAGE_ALSA_LIB_ALISP is not set
+# BR2_PACKAGE_ALSA_LIB_OLD_SYMBOLS is not set
 BR2_PACKAGE_LIBMNL=y
 BR2_PACKAGE_WPA_SUPPLICANT=y
 BR2_PACKAGE_WPA_SUPPLICANT_AP_SUPPORT=y