AudioSense-Pi

AudioSense-Pi is a RPi HAT based on a TI's stereo codec.
It is Open Source Harwdare Association (OSHWA) certified with UID - IN000007

This hardware provides audio input capabilities to the RPi.
The codec connects to the RPi's SoC through the I2S Bus.

The codec chosen, allows interfacing multiple audio I/O to the RPi.

Multiple I/O? Yes!
The following devices can be connected through a 3.5mm jack

1. Line-In: Plain old audio in from mobile phones, PCs, etc.,
2. Mic-In: Connect a microphone
3. Line-Out: Connect the output to a speaker
4. Headphones: Connect a Headphone w or w/o microphones

Simultaneous Inputs? Yes!
It supports the following combinations

1. Two stereo Line-Inputs and a microphone
2. One stereo Line-Input and two microphones
3. Two stereo Line-Inputs, a microphone and one mono line-input (with h/w hack)
4. One stereo Line-Input, two microphones and one mono line-input (with h/w hack)

Simultaneous Outputs? Yes!
Audio output can be routed to the headphones or speakers (with additional hardware)

Hardware overview

Software overview

Using the ALSA System on Chip (ASoC) layer we write a machine driver for the HAT.
With the following changes a new sound card by the name audiosense-pi will appear

1. A device tree overlay is added for hardware configuration.
2. Changes to the configuration file (config.txt).
3. ASoC machine driver, makefile and kconfig changes
4. Minimal changes to the ASoC codec driver to handle deprecated APIs

Getting started with AudioSense-Pi

Fab

1. Order the BOM
2. Send the gerber files to your nearest fab house
3. Assemble the board, it should look something like this..

Assembled Board

Preparing the SD card

We have three ways to setup audiosense

1. Get the prebuilt images, flash it into a SD card, fly away!
2. Stay with the existing image you have, build the kernel yourself and flash only the kernel image
   • Pull the raspberry pi kernel source
   • Use this script to build and flash the kernel image to the SD card
   • Edit/add the following lines to the config.txt in the boot partiton of the SD card

       # Uncomment some or all of these to enable the optional hardware interfaces
       dtparam=i2c_arm=on
       dtparam=i2s=on
       dtparam=spi=on
       
       # Uncomment this to enable the lirc-rpi module
       #dtoverlay=lirc-rpi
       
       # Additional overlays and parameters are documented /boot/overlays/README
       dtoverlay=audiosense-pi
   
       # Enable audio (loads snd_bcm2835)
       dtparam=audio=on
   

   • Boot the pi, run the command aplay -l you should see a new soundcard audiosense-pi
3. Get a kernel image that you want, merge the patches manually, build and flash the kernel image (for advanced kernel developers)
   • Clone the kernel sources you want
   • Apply the patches in the software directory (git am might not work owing to the large number of changes among the trees)
   • Use the script in step 2, apply the config.txt changes and boot the pi

Configuring the soundcard

1. Open terminal, type in alsamixer. Hit F6 and select audiosense-pi from the list of soundcards Soundcard selection
   
2. Soundcard widgets and control settings
   
3. Plug in an audio-input to the board, a headphones and run arecord -D hw:1 -c 2 -r 48000 -f S16_LE | aplay -D hw:1
4. If you did everything right, you will be listening to your favourite song ;)

License Information

Hardware licensed under the CERN Open Hardware License version 1.2
Software licensed under the GNU GPLv2
Documentation licensed under CC0 1.0 Universal