piNOS Audio System

The first project which I bring to you is the piNOS audio system. It is a kind of clone to a popular audiosystem which allows you to have audio all over your home and even synchronise it. The system comprises of a master device (including a media server) and satellites which function as mere audio players. And - as everything is APP nowadays - the whole thing of course controls through your mobile device.

Inhalt

• System description
• Hardware used/ Bill of material
• Preparing Linux (Rasbian Wheezy)
• Installing and setting up WLAN
• Installing and setting up (USB)-Audio adapter
• Installing Logitech Media Server
• Installing and setting up Squeezelite player
• Controlling the audio system
• Implementation prototype
• Implementation: Doing the piNOS system
• The piNOS Master
• The piNOS Satellite

System description ↑

A picture says more than a thousand words can do...



You might also like to check out the corresponding "Class D Amplifier" project for creating the class D audio amplifier shown in the lower right corner of the above image.

Hardware used/ Bill of material ↑

I used the following hardware during the prototype phase (for later implementation some hardware/ software componentens may change - I'll highlight that):
- Raspberry Pi Model A+ (as from teh raspberrypi.org, "Raspberry Pi is a trademark of the Raspberry Pi Foundation")
- WLAN USB Adapter, LOGILINK WL0084B (based Ralink RT5370 chip)
- minimum 1A, 5V power adapter with micor USB (e.g. ANSMANN 1000-0005)
- micro SD memory card, minimum 4GB, class 10

only for initial setup and WLAN config:
- USB hub
- USB keyboard
- computer monitor with DVI/HDMI or TV with HDMI interface

You can buy the stuff here:
- http://www.conrad.de, price on upper end of the scale, reliable quality
- http://www.reichelt.de, quick delivery, reasonably priced, reliable quality
- http://www.pollin.de, quick delivery, reasonably priced, quality questionable, documentation weak

Preparing Linux (Rasbian Wheezy) ↑

From a windows machine (that is what I'm used to use primarily):

1. use win32diskimager to copy the wheezy image to your SD memory card

2. setting up the pi-hardware
- attach USB hub, connect WLAN USB stick and keyboard
- attach SD card to SD socket
- connect HDMI cable to monitor or TV screen
- power up

3. the pi starts with the config menu
- use the keyboard cursers (up, down, left, right) and tab key for navigation

4. expand the filesystem to use all SD card memory
- select item 1 and hit enter, follow the on-screen process

5. go for internationalisation (befor changing the password!)
- select item 4 and hit enter
- select I2 to adjust time zone, follow the on-screen process, stay patient, some steps have latency
- select I3 to adjust your keyboard, follow the on-screen process, stay patient, some steps have latency

6. boot to console
- select item 3 and hit enter
- enable/ confirm the usage of "Console" (hit tab and confirm "ok")

7. for future administration, we want to use SSH, hence enable SSH
- select item 8 and hit enter
- select A4 and hit enter
- confirm enabling SSH and hit ok

8. adjust password of user "pi" [optional]

- select item 2 and hit enter
- follow the on-screen messages, enter new password, re-enter password and
confirm

9. quit the config and reboot
- when leaving the config by stepping to "finish" (use the tab key) confirm to run the reboot

AUX

* to re-enter this config menu later simply enter

Installing and setting up WLAN ↑

NOTE you'll be needing a keyboard and a monitor to carry out the WLAN
configuration

1. list your USB devices and see for your WLAN adapter


2. based on the above reference list check, if driver is alread available (and maybe already started)

3. if driver is not present, see below for next steps else continue to setup WLAN and check for networks
(assuming, that there is only one WLAN-stick present in the system)


4. adjusting wpa supplicant settings

the file should contain something like this (for a WPA2 WLAN):


5. adjusting network settings

the file should contain something like this to ensure support for multiple WLANs (if that is applicable to you):



6. restart the network environment without doing a reboot

7. check your succesful config; shows connectivity to your network - SSID

8. you can now access your pi through SSH (e.g. putty) via WLAN, the IP address
is shown by

9. ensure automatic reconnection upon WLAN losses (when ethernet is not needed)

to revert (e.g. when using ethernet again)

AUX

* in case lsusb returns a driver name and the driver is not yet installed

if found, install the driver

Installing and setting up (USB)-Audio adapter ↑

AUX

* controlling the audio output level

Installing Logitech Media Server ↑

This turtorial is based on http://allthingspi.webspace.virginmedia.com/lms.php and has been adjusted to match with current developments

With a rasbian wheezy dating to december 2014 (from the raspberrypi.org website), there are a couple of differences to the above tutorials, particularly when it comes to using squeezelite instead of squeezeslave

1. setup wlan according to description; check, that automatic wlan reconnect is enabled

2. run update

3. add some libraries => not necessary when using wheezy release 2014 or later

4. add the package patch => not necessary when using wheezy release 2014 or later

5. go to home directory

6. create two temporary directories for further files

7. switch to directory ~/logitechmediaserver

8. obtain the following files

9. install the mediaserver

this will take a while so stay patient

10. Stop the mediaserver for the moment, until all other fixes have been applied

11. unzip the tar-ball container

12. move some files, create some sym links (ln -s) and refresh dynamic linkers bindings



13. fix some permissions

14. create folder for playlist and change permissions

15. start mediaserver

AUX:

* start|stop the Logitech Media Server

Installing and setting up Squeezelite player ↑

This turtorial is based on http://www.gerrelt.nl/RaspberryPi/wordpress/tutorial-installing-squeezelite-player-on-raspbian/ and has been adjusted to match with current developments

1. go to home directory

2. create two temporary directories for further files

3. switch to directory ~/squeezelite

4. obtain the following files

5. copy the binary to the correct directory and make executable

6. copy the squeezelite settings file to the correct directory and make
executable

7. copy the squeezelite config file to the correct directory and make
executable

8. setup integrated audio/ dedicated audio card according to description

9. modify the squeeze player configuration with the audio settings



10. finally make squeezelite start on power on

AUX:

* List the available audio devices for the squeezelite player

* start|stop|update the squeezelite player

Controlling the audio system ↑

Your installation can be controlled in two ways. The one is based on an ordinary browser web application.

Access the media server via http://<IP address of master device>:9000
You will be faced with the Logitech Media Server control panel.

The second option - for Android - is based on a native application called Squeezer. You find that app from the Google Playstore. After installation you will simply have to enter the IP address of the master
device

Implementation prototype ↑

The implementation prototype focuses on the combination raspberry pi and audio
class D-amplifier.

After figuring our, that the D-amp (see for the D-amp project) was running pretty smartly in its test environment I connected the raspberry pi...and than came the problems.

The raspberry pi org-website mentions, that with the release A+/B+ the audio output capabilities had been improved - unfortunately, I cannot share this impression. The integrated audio output delivers crappy audio quality. When directly connected to the AV-3.5mm header one gets lots of noise added to the audio signal (I had measured a -60dB noise floor).

I than connected my "least" cost USB-audio adapter which is based on a C-media USB-audio chip (some 5EUR). And guess what, audio is so much better already - but still some way off HiFi. Not in terms of noise floor, that is so much better.
The point of concern is the audible pi processor and interface activity: e.g. whenever WLAN communication happens, whenever the processor is dealing with some requests (e.g. launching the Logitech Media Server website through a browser) there are clicks and humms on the audio channel. Even if audio is muted, the activities get through.

First thoughts about power supply decoupling didn't improve the situation. I tried all paths so far and even pimped the C-Media USB-audio stick. No luck at all.

I should mention, that I'm driving the whole implementation from a 35W switch mode power supply (SMPS) at 15V - it's a Meanwell device which does create some audible noise when operated at low loads. As soon as I drive the raspberry from it (with a 5V DC/DC converter daisy-chained) the noise is gone and I can drive the D-amp from it in parallel. And because the pi will run 247 I'm not concerned about the low load noise of the SMPS at the moment.

Regarding the audio issues, I'm not giving in yet: there is still room for improving here and there. The next steps will be to build an isolation pre-amplifier to separate the audio-channel. And further filtering options have not yet been tried either.

Results will follow next.

One final remark on the combination pi + C-Media USB-audio stick: I still own a revision A pi. Adding a USB-hub, WLAN stick and the C-Media stick connected to a HiFi system is giving an acceptable audio experience! So, if you intend to build your internet radio and media server combi for you existing home entertainment system you might be fine with that combination! Try it - material comes at some 40EUR, the installation takes some 1 to 2 hours depending on your Linux experience. And the solution leaves incredible room for further development under your control.

Implementation: Doing the piNOS system ↑

It's been a while since I started this whole thing and I'm writing this in Q3 2016, almost two years since the last utterings were posted on this.

Meanwhile, the implementation of the system sketched in the intro above is in operation for more than half a year now - successfully, if I may add so.

As pointed out during the proto phase - and some other enthusiast out there - power supply is the crutial point for a "clean" operation. The next two chapters will show you, how I did set up everything and which stuff is needed to get there.

The piNOS Master ↑

In retrospective setting up the piNOS Master was probably the most trivial part of the whole system to do.

The master device is holding the media server and a player. For me, the master is located close to my ordinary stereo amp and is located in a pretty much hidden location, i.e. design of enclosure was not so important.

My player connects wirelessly to the local network and also holds my audio MP3 collection on a USB stick - but that's optional and not further description will follow in here.

The Material

- 1x raspberry pi version A+
- 1x MicroSDHC-Card 4GB
- 1x LOGILINK WL0084E (seems to be no longer available; see for NOTE)
- 1x rasbian wheezy dating to December 2014
- 1x LOGILINK USB 4-port hub, internal, active (e.g. Pollin 721 663)
- 1x LOGILINK USB 2.0 5.1-Audiocontroller (e.g. Polllin 720 945)
- 1x plug-in power supply, 5V d.c., minimum 2A with barrel jack
- 1x barrel socket, chassis mount


The mechanics

The raspberry just fits in the casing of the internal USB hub. The USB hub's host port was soldered directly to the USB port of the pi but leaving out the 5V signal. The barrel socket was installed in the side wall of the enclosure and DC wiring run to the pi's and the USB hub's power inputs.

Last step is to plug the USB devices (audio and WLAN adapter) into the USB ports of the hub.

When SD is readily prepared with the Linux image, insert the SD card and close the housing. You are now ready to power on your piNOS master.

Software setup

All software setup was done according to above descriptions.

Image footage

The following images may give some impression on how the above fits together in a mechanical way:


Above: electrical wiring; note, that power supply is separated at the barrel jack. USB only connects through DP/DN (green and white wire).


Above: before closing the box, remember to insert the micro SD card.


Above: enclosure of the hub closed, pi included and fixed with screws, barrel jack mounted in the side wall. USB sticks (audio, WLAN) plugged in.


Above: power supply; sufficient to also power at least one USB stick

The piNOS Satellite ↑

In comparison to the Master device, this one tunred out to be the biggest part of the project to solve and build...and to write (yet to come).

The modules overview

The following image shows the modules which make the piNOS Satellite.



The Material

The material setup on the very basic level is equivalent to the piNOS master:

- 1x raspberry pi version A+
- 1x MicroSDHC-Card 4GB
- 1x LOGILINK WL0084E (seems to be no longer available; see for NOTE)
- 1x rasbian wheezy dating to December 2014
- 1x LOGILINK USB 4-port hub, internal, active (e.g. Pollin 721 663)
- 1x LOGILINK USB 2.0 5.1-Audiocontroller (e.g. Polllin 720 945)


In addition, I used further material as I created a complete stand alone stereo thing:

- various cuts of MDF sheet 10mm (details to follow)
- 1x toroidal transformer, 2x15VA, 1A each
- 1x Class D Amplifier board (see for "Class D Amplifier" project)
- 1x power supply board, 2x 5V (description to come)
- 1x electronic filter board (description to come)
- 2x loudspeakers, type mid-range driver, 30W sine, ca. 100mm
- 2x loudspeakers, type tweeter, 30W sine, ca. 50mm
- some wiring material
- 1x USB socket, chassis mount
- some various screws
- 2x frequency crossovers (suitable for the speakers)
- 1x EURO plug power cord

To make the enclosure look like something I made us of the following:

- some clear furniture lacquer
- some black satin spray paint
- frame dowels (for cover frame of loudspeakers, VISATION)
- some acoustic speaker cloth (check out http://www.akustikstoff.com)

My bill of material turned out to total to about 130EUR - with a potential of cost savings at around 15EUR to 20EUR.

The mechanics

I designed the enclosure of the piNOS Satellite based on the existing pair of loud speakers. For that I love to use the one of the many tools from google: sketch up.

The box during design phase looked like that:



Above: front and rear view without the cover frame.



Above: 3D CAD based collision analysis and placement study on where to put which electronic board. Also check and determine the dimensions based on the loud-speakers.

Software setup

Software setup is almost equivalent to the above description BUT the installation of the Logitech MEdia Server is NOT done - why: there is only one media server in the system that that is provided through the piNOS Master device already.

Image footage

And now some real images - bringing the piNOS satellite to life:


Above: the raspberry pi, USB hub and dual 5V power regulator.


Above: the digial amplifier, electronic filter and audio adapter.



Above: first wiring brought into place, frequency crossovers assembled to front.


Above: the USB socket has it's own chassis mount


Above: the toroidal transformer is mounted behind the right channel tweeter.


Above: the first test, speakers are assembled.


Above: rear cover assembled.


Above: USB socket in operation.


Above: piNOS satellite in operation with front cover and acoustic speaker cloth.