Making Sound Satellite

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Lab 0: Making Sound With Satellite CCRMA
Primarily by Edgar Berdahl (a few sentences by Matt Wright)



For this lab you need your Satellite CCRMA kit, a computer to program it, and some headphones with a mini 1/8" stereo jack. During this lab, you will start to use your kit.


Contents

The Satellite CCRMA Setup

Included in your kit you should have

- Satellite CCRMA Hardware (Beagle Board + microSDHC memory card + Arduino Nano + solderless breadboard)
- One 5V power adaptor to plug into the Beagle Board
- One Ethernet cable for external communication
- Arduino Nano
- One GT Max adjustable-length USB cable

If you are missing something, please go get it before assembling your kit. Use the USB cable to connect the Arduino to the Beagle Board. Make sure you plug the micro SDHC memory card fully into its seat so that it looks as shown inside the red box:

Image:Kitblank.jpg


Powering Up For The First Time

Plug the Ethernet port of the Satellite CCRMA into your laptop. Then plug in the 5V power supply into the Beagle as shown below. You should see some lights turn on, flickering every now and then. This means that Satellite CCRMA is booting up.

Image:Kitplugged.jpg


Connect To Satellite CCRMA

In order to see what your Satellite CCRMA kit is doing and program it, you need to log in to it. To do so, follow these instructions.

After you login, you will see the prompt ccrma@satellite:~$ This means that you are logged into a computer named "satellite" as the user "ccrma", and you are currently in the directory ~, which is the shortcut for your home directory.


Avoid Powering Down the Board Without Halting it First!

Would you take the battery out of your laptop and unplug its power adaptor without shutting down? I don't think so! The same goes for Satellite CCRMA, at least when you can avoid it, because it is a small computer running linux.

Now we will test the halt procedure. Run the halt command as superuser by typing sudo halt at the Satellite CCRMA prompt. Then you will again have to type in the password temppwd in order to have the privilege to run this command. The SSH connection will be closed, but it will still be 20 seconds or so before Satellite CCRMA has completely shut down. (Note: The command sudo reboot would instead have caused Satellite CCRMA to reboot itself.)

Wait an extra entire minute to ensure that Satellite CCRMA is shut down. However, it will not power itself off. To do this, you need to disconnect the 5V power adaptor from the hub.


Getting Comfortable With Satellite CCRMA

  • Turn on Satellite CCRMA again using the same procedure as before where you plug the power into the USB hub. After about 30 seconds, the board should be booted up again, so you can log in again by running the command

ssh -X ccrma@192.168.1.105


  • Run the command pwd to find out the current directory. You will find that you are in the ccrma subdirectory of the directory /home.
  • Type the ls command to see what is in the current directory. The blue items are subdirectories of the current directory. You can change directories using the cd command. For instance, to change into the pd_lecture subdirectory, you should run the command

cd pd_lecture

  • Now again type pwd to make sure that you understand where you are! Run the ls command to see what files are in here.


  • Find out if you have successfully connected Satellite CCRMA to the Internet by running the command

ping yahoo.com

  • If you get responses that take about 100 ms to 200 ms, then your settings are correct.


Starting Audio And Pd

  • First we need to start up the audio connection kit. It's easiest to do so using the graphical interface, so execute the command

qjackctl &

The ampersand (&) is there to indicate that even though you are opening a new window, you should still be able to keep typing at the old terminal. There might be some strange error message windows, but just close these to get back to the main JACK Audio Connection Kit. To start audio, click on the Start button.

  • In order to be able to hear audio, you will need to plug a pair of ear buds, headphones, or loudspeakers into the 1/8" (2.54mm) jack labeled AUDIO OUT on the Beagle Board. Be very careful when plugging the headphones in and not to pull too hard on the headphone cable! Unfortunately it comes off of the board very easily, and then you will have to buy a new board for $150!!!
  • Start pd now with the following command, where again we include &:

pd &

  • Choose Open from the File menu and select the patch 4_algorithmic_music.pd. In the main pd-extended window, click on the compute audio button. Then go back to the patch, move the speed and width sliders slightly to the right, and bring up the volume. You should now hear some sound in your headphones. Play around with the parameters to see what new sounds you can discover.

Troubleshooting: If you still do not here any sound, then probably you missed one of the steps so far. If you look at the messages in the main pd window, you might find a clue.


Documentation

  • Right-click or option-click on any object to get a contextual menu including "help," which opens that object's help patch. (If you are using a Mac and don't have a right mouse button, then go to the X11 pull-down menu, select Preferences, and make sure that Emulate three button mouse is checked in the Input pane. Now, you should be able to right-click by clicking while holding down the Command key.)
  • Right-click on a blank portion of a Pd patch. Now when you select "help" you get a list of Pd's built-in objects, arranged by category.
  • In the upper right hand corner of each Pd window is a "help" menu. This accesses the Pd tutorials as well as some online reference documentation.


Short questions

Why is the following patch a bad idea?

Image:badidea.gif

Make a patch that shows how to connect some objects together to calculate the function 1-x where x is an input number. Save the patch in a file called OneMinus.




The Community

There is a large, dedicated, and very generous community of Pd users on the Internet. Do some web searching (e.g., with a search engine, or else starting from some more specific resources) and look for interesting externals and/or patches. Download, install, and play with at least one. Here is a neat command for downloading directly to your kit using the wget command. For instance, if you hypothetically wanted to download the file off of the Internet at address http://ccrma.stanford.edu/PdPatches/SpecialPatch.pd to the current directory, then you would use the command

wget http://ccrma.stanford.edu/PdPatches/SpecialPatch.pd


For more help in finding resources, don't forget to look on the PID Links page.



Optional: Programming Linux

We don't actually expect you to do anything here, we are just providing some more information that is maybe helpful for you linux gurus. Since ccrma@satellite runs ubuntu linux on an OMAP chip, many standard software packages have been compiled for it. This is why we were easily able to install software such as Jack, Audacity, ChucK, Faust, Jacktrip, and the Arduino software.

If you are lucky, you can install your favorite software using the apt-get utility. To get a list of packages available on the OMAP's ARM architecture, type

sudo apt-cache pkgnames

You will notice that this list is way too long to look at. You can pipe it to the text file using the command

sudo apt-cache pkgnames > packages.txt

and then look at it using emacs packages.txt, or you search for a particular package, such as

sudo apt-cache pkgnames | grep emacs.

Or, you can compile linux software yourself on the Beagleboard. The gcc, g++ tools etc. are already installed.

Type the df command. You can see that there is not a whole lot more than 1GB available on the SD card, so you should only install software if you decide that you need it.


Halt Your Board Properly When Finished!

Remember to shut down your board when you are done before powering it off! (Of course as Spencer pointed out, if you are operating truly autonomously, of course you cannot login and run the halt command. Nevertheless, if it is not too inconvenient please try to shut down properly if you can. If you do not, then you may find that your SD memory card becomes corrupted.) As described above, you can do this by executing the command sudo halt and then waiting 30 seconds before disconnecting the power cables.


NMC 2011
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