Sounds Like RFID: Using a Radio Frequency Identification (RFID) Reader to Make Musical Instruments

Note: Installing the software on your computer might be a little tricky. You will do it in steps, but ask an adult or a tech-smart friend for help if you have a problem.

Setting up the Drivers and Testing the Reader

Drivers

Notes: Depending on who owns the computer you are using, get permission from your parents or your school before you download and install any software. The exact procedure for installing software on your particular computer may vary depending on how that computer is set up. If you need to, ask an adult for help installing the drivers and application software.

1. The RFID reader in the materials list will be connected to your computer via USB. That is very common, of course, but an RFID reader is not like a keyboard or a mouse; the computer will not know what to do with the data. To fix that, you need a device driver, which allows the computer to know how to access data from the reader.
2. In the RFID kit, you will find instructions for going to the Parallax website for documentation, and to the FTDI website for drivers. The RFID reader uses chips from FTDI, so it is necessary to have the drivers from their website that are specific to your computer. Drivers are available on their website for Windows XP, Vista, Windows 7 and Windows 8, and for Mac® OS X 10.6 or later. Linux systems may not need drivers, as many Linux installations already support the FTDI chipset.
3. The goal is to make the RFID reader look like a standard serial communications port. Follow the instructions provided with the kit and on the Internet to get the drivers installed. Ask an adult if you need assistance.

Serial Terminal Emulator

Here is a little background about the terms serial and terminal. It is somewhat "old school" to keep referring to "serial" and "terminals" on modern computers, but the terms go back decades (to the 1960s and 1970s) when a computer did not have a display or a keyboard. Instead, computers used a different type of port, called a serial port, which was common before USB was invented. The computer may have been in a special air-conditioned room nearby, while the user had a terminal on his or her desk that had the display and the keyboard. So we still use that terminology today when we talk about how a computer communicates with other devices, even though there is no separate terminal on most people's computers, and many computers no longer have the old standard serial port.

In this science project, you will need to look at the data coming from the RFID reader. Because of the driver you installed in the previous section, your computer will think the data is coming in on a serial port. To see the data, you need to install a program that works like an old-style terminal to display the raw data. These terminal emulators are easily found for just about any computer you will be using.

• On Windows, your computer may already have Hyperterminal installed.
• Newer Windows systems may not have Hyperterminal installed, but you can download a free program called PuTTY (the name evokes even older technology) that will do the job perfectly and is actually preferred for this project.
• Under Mac OS X, look in the app store for a program called SerialTools.
• Linux machines can use a serial terminal emulator such as minicom.

Connecting the RFID reader

Figure 3. The Parallax RFID reader connects to your computer via USB. Shown here are the required USB cable, the reader kit with the included tags, and a bag of 10 additional tags that you will need for this science project (you can use as many as you like).

1. With the device driver and terminal emulator installed, plug the RFID reader into the computer using the mini USB cable. Depending on your computer, it may take a moment or two for the computer to recognize the device. It will appear in your computer as a serial port.
   1. On Windows, it is a device that is usually named something like 'COM4', 'COM5', or some other number. Figures 4 and 5 show some sample screens from Hyperterminal and PuTTY (preferred) that you might run on a Windows computer. If using PuTTY, select the options, as shown in Figure 5, using whatever COM port is correct for your particular installation.
   2. On a Mac or Linux machine, it could be named almost anything, depending on the specifics. That's okay though, as the serial terminal software can find it. Figures 6 and 7 show a successful setup using SerialTools, a program available for Mac OS X machines.
      1. Be sure to check the 'RTS' and 'DTR' boxes to activate the RFID reader, and click on 'Connect.'
      2. Once connected, SerialTools will display any data coming in from the RFID reader.

The program Hyperterminal opens a window to attempt to connect to an RFID reader plugged into the computer.

Figure 4. Hyperterminal is one program you may already have on a Windows computer. The RFID reader will appear as one of the higher-numbered COM ports.

The program PuTTY is opened to a setting configuration window. In the session tab there is an option to attempt to connect to a peripheral device that is inserted into the computer with a serial connector. Other options for connection types, speed, and sessions are also available in the window.

Figure 5. PuTTY is a very popular terminal emulator that runs on just about any version of Windows. It is a better choice than Hyperterminal if you have permission to install software on your computer. Select the options, as shown, using whatever COM port is correct for your particular installation.

The program SerialTools for OS X has a drop down menu that displays devices connected to the computer. Options can be changed for baud rate, bits, parity, stop bits, RTS, DTR, CTS, DSR, cr/lf, raw and local echo.

Figure 6. SerialTools for OS X will show you a list of serial ports it found on your computer. In this example, it thinks it found some Bluetooth serial ports as well, but we connected through USB, so select the one with USB in the name. Be sure to check the 'RTS' and 'DTR' boxes to activate the RFID reader, and click on 'Connect.'

When an RFID reader is connected to the SerialTools program, data from the reader will be sent to a small window in the bottom of the program. There is an option to disconnect on the right side of the program window.

Figure 7. Once connected, SerialTools will display any data coming in from the RFID reader.

2. Start the terminal emulator software. In the software's menus, you will find a place to select the device. You probably do not have many serial devices connected, so it should be easy to locate the correct port. The RFID reader uses 2400 baud, 8 bits, no stop bits (you can look this up if you want to know what that means). Select these options in your communications software.
3. To check if you got it right, take one of the tags that came with your RFID reader and wave it within a few centimeters of the reader. You should see a 10-digit number appear on the screen.
   1. If you do, that is awesome! You got the configuration right and are ready to proceed.
   2. If not, you may need to restart the computer to get the driver activated, or you may have selected the wrong serial port in the terminal software. Is the LED on the reader lit? If not, check that you have a working cable and that you plugged the cable into a working USB port.

Note: The tags in this kit each contain a unique 10-digit identifier. The program you will write takes advantage of that to tell which "bell" you are ringing.

Finding or Installing Python 3.x on Your Computer

4. The rest of this procedure uses Python 3.x as the programming language to read the data from the tags and starts the corresponding sound. Depending on your computer, Python might be started from a command window, or it might be a clickable icon, possibly labeled "Idle" or "Idle3." Look for some indication of Python being preinstalled.
   1. If you find it, start it up and see what version you have. We recommend version 3 if you plan to use our sample code.
   2. If you do not have version 3, you can look at the python.org website to download the correct version for your computer.
5. Download and install Python 3.x according to the directions. Again, if you need help, ask an adult or tech-smart friend.

Installing pySerial

6. You have Python 3? Great! The bad news is that Python does not know how to talk to connected devices like your RFID reader. To fix that, you need to install a module called 'pySerial' that you can get from pypi.python.org. Note: Installing it can be tricky sometimes. We suggest that you do an internet search for "pyserial install python 3 windows", "pyserial install python 3 OS X" (for the Mac), or "pyserial install python 3 linux" to get started.
7. To make sure you have pySerial installed correctly, start up Python and load the program 'showtags.py' that you downloaded from the Materials list. Edit the program to show the name of the serial port that you determined when you ran the test with the serial emulator in steps 2 and 3, above. You should see something on your screen similar to Figure 8.

Sample code in Phython is color coded and written to connect to an attached RFID reader. Output from the reader is taken by the program and displayed on the computer.

Figure 8.The sample Python program 'showtags.py' will simply display the tag data as it comes from the reader.

8. Programs that acquire data have the problem of dealing with devices that can send information any time they like. If you write a program that asks a user to type something in, the program will ask, and then wait for a response. We cannot do that with the RFID reader; it will send whatever it knows as soon as it knows it. To handle that better, this program takes advantage of a concept called threading, where one program starts acting as if it is two or more programs working together. Python does threading really well, so this program takes advantage of it. You might find it helpful to open the 'showtags.py' file in Python or a text editor/word processor as you read this description of how it works.
   1. The first four lines simply tell Python that you are using some extra features. In this case, serial (pySerial, to be precise), threading, time (so you can accurately time things), and sys (for system functions).
   2. The next two lines tell the program which serial port you want to talk to (use the name you found earlier), and what 'baud' rate the data comes in. That term refers to bits transferred per second and the RFID reader uses 2400.
   3. Next, you tell Python to establish a connection to the serial port. You give it the name and speed, and it stores a handle. This handle is how the program will talk to the open port.
   4. You then define two helper functions.
   5. The first one, handle_data(), will be called when a tag has been completely read in. You saw the format of the messages when you ran your serial terminal test earlier. This function does not do much now; it simply displays the data on screen. You will use it later to play sounds.
   6. The second helper does the heavy lifting. read_from_port() will loop forever trying to read data from the RFID reader. The data coming from the port will be 12 characters per tag: 10 digits of a unique number followed by 2 characters to indicate the end of the data. This function collects it all up and when it is complete, it calls handle_data() to turn that into something useful.
   7. With the helpers defined and the port open, the next step is to start the read_from_port() running in its own thread. That frees you up to do other things like play sounds. You need to set up a thread, start it running, then print out a message. Finally, you cannot just end, so you loop forever doing nothing, assigning the value 0 to a variable. You could do something else here if your program had something to do. If some parts of this program do not make sense to you, you can find explanations of the Python and the pySerial functions on the Internet or in a Python reference book.

Installing pygame

9. Do you have pySerial and your RFID tag reader working? Time to make some noise! Python has a module just for games, called 'pygame'. It offers the ability to play sounds, play large sound files, read from joysticks, display graphics, and other things that you might want if you are planning to write games in Python. Too bad it does not read RFID tags! You need to install 'pygame' that you can get from pygame.org. Note: The web page offers some installation instructions that might or might not be helpful. We suggest that you do a search for "pygame install python 3 windows", "pygame install python 3 OS X" (for the Mac), or "pygame install python 3 linux" to get started. It is a bit easier to figure out than pySerial.
10. Copy 'playsounds.py' that you downloaded from the Materials list into a directory on your hard drive. You also want the file 'Bell_sounds.zip' which is a selection of notes played on handbells. Put the sound files into the same directory as 'playsounds.py'.
11. Start up Python and load 'playsounds.py'. Run the program and you should hear two tunes played on handbells.
12. Step by step, this is how playsounds.py demonstrates two ways of using pygame to play sounds. First, as shown in Figure 9, you have to initialize the sound system. Import the necessary modules (you always have to do that) and then call pygame functions to set up its sound mixer. You can see a complete listing of pygame functions on the pygame site (link shown earlier).

Sample code in Phython that will initiate a sound mixer in pygame. The commands are pygame.init() and pygame.mixer.init().

Figure 9. To play sounds using pygame, you must initialize pygame's sound mixer.

Example code in Python that loads sound files so they can be played with functions.

Figure 10. This is one method you might use to play sounds. We do not suggest this one, but you will find it on the Internet and it is easy to do.

13. To play a sound file of any length, you can simply use the pygame "load()" and "play()" functions. The drawback is that the program has to pause and read the file, which will slow things down a bit, and you can only play one file at a time. With real handbells, you often hear the whole group playing at once. Another problem with this method is that it takes up a lot of program space to decide which file to play. When you write your program that reads the tags, you might end up with something like:

    If tag=1 then play("C")
    If tag=2 then play("D")
    ...etc

That is okay if you have a few tags, a few notes, and only one kind of sound. Imagine you had dozens of tags for dozens of notes and several different kinds of sounds. This might not be the most efficient way of writing your program. The little code snippet in Figure 10 is okay, but...

14. There is another method that creates a list of items that has the sound file name (preloading into the pygame mixer), a space for an RFID tag that you will associate it with later, and a friendlier name. On handbells, the piano, or many other instruments, the octaves are numbered; the lowest is 0 and the highest is 9. This is called scientific pitch notation (see the Bibliography for a link to more information) and is commonly used in reference to handbells. Whether or not the pitches represented in the files are exactly these octaves does not matter. The idea is that using "C4" to represent a C that is one octave lower than "C5" is simply easier. The list of items contains these "friendlier" names. You can then take each of these lists (one per note) and make a list of them. It takes up a lot less space than all of the other 'if-then' tests above. It makes a rather primitive database of notes and their relationships to RFID tags and note names.

Example code in Python that loads sounds and gives each sound an associated note. The sound functions are renamed based on the note and can now be played more easily.

Figure 11. Another way to play sounds in Python.

15. After the list of lists is a helper program that will search this database, find the sound by name, and then play it. Once the helper program is defined, you can use it to play a little song.

Writing Your Program

16. Now you have a way to read the RFID tags and a way to play sounds. You are almost there. Now you need to write a program that watches for tags and, when it sees one, decides what note to play and plays it. There is no handy example code here, but we are sure you will have fun figuring that out! Consider, too, that some people may not be fond of handbell music. They might like cats meowing out a tune instead, or maybe cows. Can your program play the same notes, but switch from bell sounds to another sound? Consider putting a picture of a bell on one, a picture of a cow on another, and use those tags to switch sounds.

Making It Look like an Instrument

Sure, your program is quite cool and you have sufficiently annoyed everyone in your house with "Mary Had A Little Lamb" as mooed by a meadow full of cows. But waving little tags in front of the reader does not feel a lot like a musical instrument. Continuing with the handbell theme, you can use paper cups and plastic knives to make paper handbells, as shown in Figure 12. Put the tags inside and they will look more like the real thing.

Figure 12. Simply hiding the tags in "handbells" made of paper cups and plastic knives will make people take notice when your little paper bells sound like the real thing.

1. Use your craft knife and make a small slit in the bottom of a cup. Keep it as centered as possible.
2. Insert the plastic knife into the slit. To get it in the right place, place the cup, mouth side down, on a table. Press the knife down until it just touches the table. You do not want it to stick past the lip of the cup.
3. Use hot glue on the outside of the cup to hold the knife in place. Be sure to protect your work surface in the area where you are using the hot glue; it can get a little messy. Do not to touch the glue while it cools. They call it hot glue for a reason! Have an adult around in case you need help.

Figure 13. With the plastic knife stuck through the slit in the bottom of the cup, put a glob of hot glue on both sides of the knife to hold the cup in place.

4. Once the glue on the outside is cool, turn the cup over and do the same on the inside. You need a good bit of glue to make sure the cup does not wiggle when you play the handbells. See Figure 14.

Figure 14. Put some hot glue on each side of the knife inside the cup. It is hard to do this neatly; just do the best you can.

5. Use a small bit of tape to tape one of your tags to the tip of the knife. You want it to be right at the tip, as shown in Figure 15. If you know you are not going to reuse these tags for anything and want to hot glue them instead, that is okay too. We do not suggest it, though, as you will probably find all sorts of uses for this RFID reader and the tags.

Figure 15. Tape an RFID tag to the knife blade, as close to the tip as possible.

6. Use the showtags.py program and read the tag you just taped to the knife. Write down the tag number. Decide which note this handbell will be and write it on the cup using the permanent marker. Is it C4? D4? Pick one for each handbell.

Figure 16. A whole set of paper handbells.

7. Once you have made 10 or more handbells and assigned the tag in each to a note, you are ready for a concert! You will need some music, though. Here are several ideas of how to obtain music:
   1. The music teacher at your school may have some you can borrow.
   2. The grothmusic.com website listed in the Materials list is a good start.
   3. You can find music on the Internet.
   4. Use the sample sound files included in the Materials list; however, they do not have sharps and flats. More files may be available on the AnOctaveOfCows.org website in the future. You can also make your own sound files.
   5. Are you a singer? Sing each of the notes and record yourself. Save the results as .WAV files and then "play yourself" as handbells.
   6. Maybe you have dogs that howl, or maybe you know how to make musical water glasses. Record your best sounds and play those with your bells. Note: The AnOctaveOfCows.org website is collecting sounds to share with others doing science projects like this, and they may be able to use yours. Have your parents send them an email.