MP3-RaspberryPi-Buildroot

Mp3 player made for raspberry pi 3 using buildroot.

Features

Can be controlled using 4 buttons:

Start/Stop
Next
Previous/Restart
Shuffle

Can be controlled using keyboard commands:

start
stop
next
prev
restart
shuf
connect (This is used to connect Bluetooth manually, as there are some issues in automatic Bluetooth connection "Trust").
remove (This is used to disconnect Bluetooth manually and remove the device from the device list).

Note: In case of connection problem, try remove then wait a bit (1-2 minutes) for scan to discover the device again, and connect

Can be accessed with ssh through Ethernet (IP: 192.168.5.30), or WiFi (IP: 192.168.1.30).
Can be accessed using serial terminal (with TTL module).
Voice output can be audio jack, HDMI, or Bluetooth. The system can switch between them automatically.
You can insert your own songs via a Flash USB. If your USB is detected, the system will count how many songs available and notify you with text-to-speech.

How to use

Move mp3_rpi3_defconfig to configs directory in buildroot.
Use this command:

make mp3_rpi3_defconfig

Use menuconfig to change the path to mp3_overlay, mp3-post-build.sh, and mp3-post-image.sh
Or you can change them manually in the mp3_rpi3_defconfig file before step 2

Note: Be sure to include the path to mp3-post-image.sh before the default post-image.sh of Raspberry Pi, as to be executed before generating sdcard.img

Edit the following files to suit you:

mp3_overlay/etc/wpa_supplicant/wpa_supplicant.conf: Add your netword ID and Password.
mp3_overlay/etc/network/interfaces: Change IPs to be compatible with your network.
mp3_overlay/MP3/audioDeviceManager.sh: Add the MAC address of your Bluetooth audio device.
mp3_overlayMP3/readInputs.sh: Add the MAC address of your Bluetooth audio device.

make and enjoy :D

Tutorial

First, we need to load basic Raspberry Pi 3 configurations through the command:

make raspberrypi3_defconfig

As we're using rpi-userland for HDMI detection, make sure you start with 32 base (The package is not available for 64 base).

Menuconfig

make menuconfig

Toolchain

We need to use glibc instead of uclibc, as available mp3 applications (madplay, mpg123, sox) need this to start working

System Configuration

We need to update our device manager to be able to recognize WiFi and Bluetooth interfaces (You can use mdev, or eudev)

Also, since we didn't allow ssh empty password in sshd_config, we'll need to assign a password for root user

Don't forget to add paths to overlay folder, post-build script, and post-image script.

Notes:

Don't remove the path for the original Raspberry Pi post-build script or post-image, instead just separate paths with a space :D
The rpi default post-image generates the sdcard.img. So, you have to execute the mp3-post-image first.
This is done by providing the paths to post-image scripts in order (mp3 first, default second) as found in our defconfig.
IMPORTANT: the default post-image for 32 base add miniuart overlay in config.txt because of the input argument passed to the post-image, which occupies the chip used for Bluetooth (terminal: ttyAMA0) and uses it for serial. So, you have to remove the extra argument passed to post-image!

Filesystem Image

The size of the image need to be increased for extra packages

Basic Audio Support

First, we need to enable sound card through /boot/config.txt. The post-image script adds this line to output/images/rpi-firmware/config.txt

dtparam=audio=on

In Libraries --> Audio/ Sound Support, we enable ALSA support through alsa-lib (All)

In Libraries --> Audio/ Sound Support, check port-audio with ALSA support

In Target packages --> Audio/ Video, check alsa-utils (Check them all :D)

In Target packages --> Audio/ Video, we need a suitable mp3 player (madplay, mpg123 ..etc).
For Bluetooth problems, sox was our best option. It can be used to play music using play command.

ssh Support

In Target packages --> Networking, check openssh

Also, The post-image script adds this line to output/images/rpi-firmware/config.txt

enable_uart=1

for enabling UART on the serial terminal (ttyS0).

WiFi Support

In Target packages --> Hardware handling --> Firmware, we need to enable WiFi firmware: rpi-wifi-firmware

In Target packages --> Networking, check ifupdown (Most probably, this will be already checked)

In Target packages --> Networking, check wpa_supplicant (Be sure to check the following options):

Enable nl80211 support
Enable autoscan
Install wpa_passphrase binary

In mp3-overlay folder, you need to configure wpa_supplicant to your network using your ssid and password. /etc/wpa_supplicant/wpa_supplicant.conf

You can also change IPs through: /etc/network/interfaces

HDMI Support

HDMI is already supported, but you will face a problem with the audio output if HDMI wasn't connected before booting. So, our post-image adds these lines to output/images/rpi-firmware/config.txt

hdmi_drive=2

For HDMI detection, tvservice is used (userland package).

In Target packages --> Hardware Handling, include rpi-userland

To switch audio output to HDMI, just write this command:

amixer cset numid=3 2

To switch audio output to audiojack, write this command:

amixer cset numid=3 1

This is done in /MP3/audioDeviceManager.sh

Bluetooth Support

The chip used for Bluetooth in Raspberry Pi is by default used for the serial terminal, so we need to change that through /boot/cmdline.txt Instead of using ttyAMA0, we write ttyS0; so ttyAMA0 can be used as Bluetooth interface.

The post-build script swaps those two in output/images/rpi-firmware/cmdline.txt

In Target packages --> Hardware handling --> Firmware, we need to enable Bluetooth/WiFi chip firmware: b43-firmware

In Target packages --> Networking, check bluez-utils 5

In Target packages --> Networking, check bluez-tools

Since alsa doesn't support bluez 5, we have one of 3 options:

ALSA + Bluez (<=4): However, support for bcm43xx was introduced in Bluez 5. So, it's hard to bring up the bluetooth interface using older Bluez versions. We tried replacing hciattach binary with that of Bluez 5. The interface was up, connected to headset, but no sound output.
ALSA + Bluez 5 + bluealsa: This should be a valid option. However, there's a problem with alsa not recognizing bluealsa as a pcm, although the bluealsa configurations exist.
ALSA + Bluez 5 + PulseAudio: This has been the most successful option. Although you'll need to start PulseAudio as a system daemon, and modify some configurations, so ALSA wouldn't bring PulseAudio down.

Needed packages for option 3:

In Target packages --> Audio/ Video, include pulseaudio (start as system daemon)

Our mp3-overlay changes some pulseaudio options to work on Bluetooth properly.

In Target packages --> Libraries --> Audio/ Sound, include sbc

Text-to-Speech

In Target packages --> Audio/ Video, include espeak

Busybox config

make busybox-menuconfig

rfkill

you might have problems with your network interfaces (They can be blocked for some reasons). A good diagnostics step is to use rfkill. This can be found in Miscellaneous Utilities.

shuf

For shuffling, we used $RANDOM in our scripts. However, if you prefer shuf command, you can enable this via Coreutils.

References

WiFi

https://blog.crysys.hu/2018/06/enabling-wifi-and-converting-the-raspberry-pi-into-a-wifi-ap/

Bluetooth

General:

Bluez 3 problems:

https://www.raspberrypi.org/forums/viewtopic.php?t=147919&start=25

PulseAudio problems:

Bluealsa problems:

RPI defconfig for base 32 problems:

https://stackoverflow.com/questions/44554255/bcm43xx-init-initialization-timed-out-with-buildroot-raspberry-pi-3-hciattach

HDMI

https://www.raspberrypi.org/documentation/configuration/audio-config.md

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