SUMMER 2016 ECE 103 ENGINEERING PROGRAMMING MUSIC SYNTH PROJECT TECHNICAL GUIDE ECE DEPARTMENT PORTLAND STATE UNIVERSITY

Transcription

1 SUMMER 2016 ECE 103 ENGINEERING PROGRAMMING MUSIC SYNTH PROJECT TECHNICAL GUIDE ECE DEPARTMENT PORTLAND STATE UNIVERSITY

2 Table of Contents Introduction... 2 Project Requirements... 2 Hardware... 2 Software... 2 Extra Credit... 3 Circuit Construction... 4 Audio Amplifier IC... 5 Speaker... 5 Assembly... 6 Operation Hints... 7 Appendix I Music Scales... 8 Appendix II Song file format

3 Introduction The Music Synthesizer project uses the LabJack to create musical tones that go to an amplifier circuit and are heard through a speaker. For information on music notes and scales, see Appendix I. Project Requirements Hardware Construct an audio amplifier circuit. Add LEDs for visual flair For specific construction details, review Circuit Construction. Software At minimum, the core program should support these tasks: Activate the FREQOUT mode of the LabJack Allow the user to specify a song file to play (see Appendix II for format details) Open and read in the note data from the external song file Translate the song notes to timer control parameters that will play back musical tones Handle a three octave range (3 to 5) Flash a specific LED depending on the frequency value of a note 2

4 In addition to the core program s specifications, these are also required features: 1. Your program must include a diagnostics mode that allows the user to test individual parts of the hardware and software. o Create a menu to select a particular diagnostic, such as testing the LEDs or playing individual tones. o You are expected to have a minimum of three diagnostic tests available, though implementing more is fine. A modular program design will make this easier. o Justification: During the development phase, diagnostics let you test system features as they are being completed without needing everything to be fully working. Imagine that just before your final demo, your project ceases to function properly. Diagnostics allow you to check each major hardware or software piece separately to narrow down the possible failure points. 2. Your program must have a user interface that utilizes functions from a terminal I/O library. o This can be done by using the obsolete conio library, which is still supported by both MinGW and Visual C. Altenatively, you can also try the pdcurses library, which is more modern and full-featured but slightly complicated to install and use. o At minimum, your user interface should look nice and utilize these terminal features: Clearing the screen (e.g., clrscr) Moving the cursor to a specific screen location (e.g., gotoxy) Controlling the foreground or background color of screen text to liven up your interface (e.g., textcolor) Reading single key presses for menu selection (e.g., _getch) o OPTIONAL: If you have the time, try using the line drawing characters from the IBM extended character set to draw boxes around control/status panels or menus. o For information on terminal I/O functions, refer to the terminal guide in the Technical Resources module on D2L. Sample code is also provided for you to study. Extra Credit To earn extra points, you can add features to the core program: Extra credit is strictly optional. Extra credit will not be accepted unless the core program works correctly first. The amount of extra credit you receive is up to the instructor s discretion. Be bold and creative to get the most credit. 3

5 Circuit Construction Each team will receive a special kit with the parts required for this project. Qty Notes Item 1 TDA7052A IC (Audio amplifier, 1.1 W, mono) (See TDA7052A_Data_Sheet.pdf ) μf capacitor (35 V, 20%, radial, polarized) 1 1 μf capacitor (50 V, 20%, radial, polarized) μf capacitor (50 V, 20%, monolithic - marked 104 E5Z) μf capacitor (50 V, 10%, ceramic - marked 474) kω Potentiometer (variable resistor - marked P104) 1 1 kω resistor (BRN-BLK-BLK-BRN : ±1%) 1 10 kω resistor (BRN-BLK-ORA : ±5%) 1 Speaker (Ferrite, 2", 8 Ω impedance, 0.2 W, 420 Hz- 5 khz) 1 Assorted LED lights The LEDs are not included in the special kit. You can find them in the standard parts kit that comes with the LabJack box. The TDA7052A is mounted in its own IC socket. The 100 μf and 1 μf capacitors are polarized, meaning that they have distinct positive and negative terminals. The negative side of the capacitor should be connected to ground (GND). There is a minus sign printed on the body of the capacitor that marks the negative side. 100 μf (polarized) 1 μf (polarized) Warning: If a polarized capacitor is connected backwards, it may be destroyed! The 0.1 μf and 0.47 μf capacitors are not polarized, so it can be safely connected either way. 0.1 μf (non-polarized) 0.47 μf (non-polarized) Warning: The speaker's solder points and wire leads are delicate. Handle them gently! 4

6 Audio Amplifier IC The project uses the TDA7052A chip, which can amplify a mono audio signal to an output power of 1 W. Label Pin# Function Description Vp 1 8 OUT- Vp 1 +5 V supply voltage IN+ 2 Positive input signal GND1 3 Signal ground VC 4 DC volume control OUT+ 5 Positive output to speaker GND2 6 Power ground n.c. 7 Not connected OUT- 8 Negative output to speaker IN+ GND1 VC TDA7052A n.c. GND2 OUT+ The Vp pin connects to a +5 V DC source (e.g., VS on the LabJack) and provides power to the chip itself. The GND2 pin is the ground for the supply voltage. The IN+ and GND1 pins are the input terminals for the amplifier. The OUT+ and OUT- pins are the output terminals for the amplifier. The VC pin controls the amplifier output volume. Speaker The 8 Ω speaker provides output for the audio amplifier. Speaker 5

7 Assembly Use the following schematic as a guide: VS (+5 V) 100 µf µf Note: All of the ground symbols ( ) on the schematic should be connected to GND on the LabJack. FIO4 (FREQ out) 10 kω 1 kω 0.47 µf 1 (Vp) 2 (IN+) 3 (GND1) 4 (VC) (OUT-) 8 (n.c.) 7 (GND2) 6 (OUT+) 5 Speaker (8 Ω) TDA7052A + 1 µf 0 to 100 kω potentiometer The notch on the chip provides an orientation reference for the pins. The 100 μf and 0.1 μf capacitors filter out noise in the power bus. The 0.47 μf capacitor blocks unwanted DC voltage from reaching the input of the amplifier. The 1 μf capacitor and 100 kω potentiometer control the volume of the amplifier's output. The 10 kω and 1 kω resistors work as a voltage divider. The voltage coming from the LabJack's FIO4 terminal is too high, so the divider brings it down to a safer level. All of the grounds in the system should be connected together. The speaker leads are connected to OUT+ and OUT-. Do NOT connect the speaker to ground! Pin 7 is not connected to anything. The potentiometer is a three-terminal device. The middle terminal is called the "wiper", which corresponds to the arrow that touches the resistor. When configured as shown, the potentiometer becomes a variable resistor. The resistance value can be set between 0 Ω to 100 kω by using a screwdriver to turn the plastic screw on top of the potentiometer's housing. Connect the LEDs (as many as you need) to the available FIO channels. 6

8 Operation Hints!!! WARNING!!! The TDA7052A can pump out 1 watt of power when the volume control is turned all the way up. This could potentially damage the speaker, since it is only rated to about 0.2 watts. To save you the expense of buying a new speaker and delaying your project (and to protect you from the angry looks of people nearby), always set the volume control to its lowest level and gradually increase it to a comfortable level. Note: As the volume goes up, the current draw of the amplifier will rapidly increase. If the amplifier draws too much current, it could cause the LabJack to malfunction. When operating in the FREQOUT timer mode, the LabJack can generate a square wave output signal at a specific frequency. If the frequency is in the audio range, the signal can be amplified to drive a speaker. Note: Due to the sharp edge transitions of a square wave, there are higher order harmonics in the spectrum that adds some "harshness" to the audio output, at least when compared to a pure sinusoid. Amplitude Time Period Frequency = 1 / Period The LabJack functions needed for FREQOUT operation are discussed in the LabJack-C programming guides. The LabJack company wrote a data file (CSV format - open with text editor or import into Microsoft Excel) that contains a table of all possible frequency values and the timer parameters needed to generate each frequency. The compressed file (in ZIP format) is called U3_FreqOutList_Hz_Base_Divisor_Value.zip. Since there are so many more notes in the three octave range than there are available LEDs, you will have to let each LED represent a "band" of note frequencies. Arrange the LEDs to make the light display visually interesting to the user. 7

9 Appendix I Music Scales The project will not require you to delve into music theory or practice. All you need to know is the frequency associated with each note in a song, so you can generate a tone at that frequency using the LabJack. To keep things simple, you will use an "equal-tempered" music scale over a three octave range. The range is purposely limited due to the poor frequency response of the cheap audio speakers used for the project. Frequencies for equal-tempered scale Subscript number is the octave group. Superscript # means sharp. Superscript b means flat. Note Frequency (Hz) Note Frequency (Hz) Note Frequency (Hz) C C C C # 3 / D b C # 4 / D b C # 5 / D b D D D D # 3 / E b D # 4 / E b D # 5 / E b E E E F F F F # 3 / G b F # 4 / G b F # 5 / G b G G G G # 3 / A b G # 4 / A b G # 5 / A b A A A A # 3 / B b A # 4 / B b A # 5 / B b B B B Original source for the table (which includes an extended octave range): 8

10 Appendix II Song file format A song file has these properties: The file is an ASCII formatted text file. The number of lines allowed in the file is unlimited. Each note occupies a single line in the file. Each line in the file ends with a newline ('\n'). The format of each note line looks like this: NO(D) o N is the note: C, D, E, F, G, A, B Cb, Db, Eb, Fb, Gb, Ab, Bb (flats) C#, D#, E#, F#, G#, A#, B# (sharps) o O is the octave range: 3, 4, 5 o D is the duration multiplier of the base time (the parentheses are required) There is no whitespace between the parts of the note. Blank lines are allowed in the file and should be ignored during processing. Comment lines start with the % symbol and should be ignored during processing. 9

11 Note: All sample songs are arranged by Ken Roberts, musician and PSU ECE alumnus. Example The sample song file "Frère Jacques" looks like this: % Frere Jacques % Arranged by Ken Roberts E4(2) E4(2) G4(2) A4(4) G4(2) A4(4) A4(1) B4(1) A4(1) G4(1) A4(1) B4(1) A4(1) G4(1) A3(2) D4(4) A3(2) D4(4) A few interpretations from the file (assume the base time is one second): "D" note, 4th octave, duration multiplier of 2 (total duration of two seconds) "F sharp" note, 4th octave, duration multiplier of 2 (total duration of two seconds) B4(1) "B" note, 4th octave, duration multiplier of 1 (total duration of one second) A3(2) "A" note, 3rd octave, duration multiplier of 2 (total duration of two seconds) 10