rpi-low-latency-audio

This is a toolset to create headless embedded systems with a ligheight Arch Linux that boots within seconds and performs real-time tasks. It is currently tested with the Raspberry PI 2, but due to its generality it should run on other ARM SoCs too.

It's initial focus is on real-time audio processing.

• easy Wi-Fi adapter management that automatically creates a hotspot if no wireless network is available. The SoC will always be accessible, even without any network infrastructure or cable (only a WI-Fi USB dongle is needed)
• It can boot into a RAM disk so the SD-Card module can be disabled. This increases real-time reliability

This repo includes:

• Generic Toolchain for partition of SD-Card and incremental arch linux deployment
• Minifier to reduce the compelete OS size to about 200MB (for small ramfs images)
• Custom systemd services for initial boot automation
• WiFi hotspot and WiFi client management
• A QEMU-emulated chroot script to chroot into the embedded root file system on any non-ARM (x68/x64) linux host system (e.g. to install additional packages through pacman)
• Configuration service that enables configuration through a FAT-partition from a Windows machine
• Some boot optimization techniques (not all possible). The aim is to get the system to boot within 5 seconds

You will never need to do any manual configuration/SSH connection to the embedded system. Comfortably prepare/maintain the OS on your linux machine or virtual machine. Changes can be deployed quickly through an icremental sync with the SD-Card or over SSH.

Getting started

• Clone this repo on a linux host (required packages on host: bsdtar sshfs qemu binfmt-support qemu-user-static )
• Get root permissions su root
• Run ./fix-permissions.sh to setup attributes and create empty directories in ./root (requires an automatic download of the latest arch linux release)
• Create SD card partition with ./init-sd-card.sh

The above in a single command where sdX is the SD-card: DEV=sdX && ./fix-permissions.sh && ./umount-sd-card.sh $DEV && ./init-sd-card.sh $DEV && ./copy-to-sd-card.sh && ./umount-sd-card.sh $DEV

Additionally installed Packages

• irman
• dnsmasq (DHCP server)
• hostapd (WiFi hotspot)
• jack2

system.d services

create_ap.service hostapd.service streamer.service

Need Remove

xinit, anything x

Scripts

/root/remount_root_rw.sh /root/arm-dev/start-streamer.sh

Dev files files (should be modulized in external repos TODO)

/root/arm-dev/udp2jack

rpi-low-latency-audio

• Arch linux for RPI2
• root file system located in root/

You should clone as root, not with sudo:

git clone https://github.com/rtaudio/rpi-low-latency-audio.git

Additionally installed Packages

• irman
• dnsmasq (DHCP server)
• hostapd (WiFi hotspot)
• jack2

system.d services

create_ap.service hostapd.service streamer.service

Need Remove

xinit, anything x

Scripts

/root/remount_root_rw.sh /root/arm-dev/start-streamer.sh

Dev files files (should be modulized in external repos TODO)

/root/arm-dev/udp2jack