Michael Dushkoff
This is a simple sound library for mbed. This sound library uses a Ticker to simulate a 50% duty cycle pwm signal on any pin. The frequency of this signal can be varied to allow sound to be created by any piezoelectric device that is connected to that pin.
Dependents: SuperMbedBall Tono
About
This library allows for a buzzer (or piezoelectric device) to output sound based on any inputted frequency. The library provides predefined note frequencies which make song writing convenient. These definitions can be found here. Some pins may not be able to drive output such as the AnalogIn pins on the LPC11U24 model. Only pin 21 seemed to work well so far on this model.
Hardware
One wire from a buzzer is connected to any pin on the mbed and the other wire is connected directly to ground. To reduce the volume of the buzzer, an optional resistor can be connected in series as shown.
Circuit diagram constructed using CircuitLab.
Usage
A music object is constructed in the following way:
Constructor
#include "Music.h" music ms(p21);
This code snipped attaches a frequency modulating Ticker to the specified pin.
This frequency can be modified by setting:
Frequency
ms.freq(240);
To allow more complex behavior, a parsing function is included that can take in strings of formatted input and turn them into songs. This input must be formatted as specified below:
- A capital letter must be present to specify the note, or R to specify a rest (Only letters A-G, and R are valid)
- An octave must be specified which is any integer from 0 to 8 inclusive
- An optional sharp sign ( # ) can be added to augment the note a half step
- A colon ( : ) must separate the octave and note from the duration
- The duration must be an integer greater than 0, and less than or equal to 64
- To separate notes, a semicolon ( ; ) must be used
Furthermore, the length of the string must be specified in order for the entire string to be parsed and a tempo must be provided (beats per minute). An example of this is shown below:
Play a Song
/* This is a test song */ char s1[] = "E4:8; E4:8; R:8; E4:8; R:8; C4:8; E4:4; G4:4; R:4; G3:4; R:4;"; int len = 61; /* Set up music pin on pin 21 */ music m1(p21); double tempo = 180; m1.play(s1,tempo,len);
This code plays the familiar 7-note opening to the Super Mario Brothers theme song. The possibilities for music creation are limited only by the hard memory limits of the mbed.
Music.cpp
- Committer:
- mdu7078
- Date:
- 2013-04-30
- Revision:
- 2:c33ed3d85f97
- Parent:
- 1:51cf7b1a96bd
File content as of revision 2:c33ed3d85f97:
/* * * * * * * * * * * * * * * * * * * * * * * * * * *
* This is a simple music library for the mbed. *
* *
* Created by: Michael Dushkoff (mad1841@rit.edu) *
* * * * * * * * * * * * * * * * * * * * * * * * * * */
#include "mbed.h"
#include "Music.h"
#include "Notes.h"
/*
* This is the minimal constructor that creates a music object
* with 0 initial output frequency on a specified pin
*
* M0 - The pin to output on
*/
music::music(PinName M0) : _M0(M0){
_flipper.attach(this,&music::flip,0);
}
/*
* This constructs a music object which has an initial frequency
* equal to a given one
*
* M0 - The pin to output on
* freq - The initial frequency
*/
music::music(PinName M0, double freq) : _M0(M0), _freq(freq) {
_flipper.attach(this,&music::flip,1/(2*_freq));
}
/*
* This changes the current output frequency to a given one
*
* freq - The given frequency
*/
void music::freq(double freq){
_freq=freq;
_flipper.detach();
_flipper.attach(this,&music::flip,1/(2*_freq));
}
/*
* This is an internal flipper that allows for a fixed
* frequency oscillation.
*/
void music::flip(){
_M0 = !_M0;
}
/*
* This initializes a given m_song to a given size
*
* *m - The given m_song
* num - The given size
*/
void music::init_song(m_song *m, int num){
m->len = 0;
m->note = new music_note[((int)(num/5))];
}
/*
* This deallocates an m_song by deallocating the notes
* that it contains and setting the length to 0
*
* *m - The given m_song
*/
void music::dal_song(m_song *m){
m->len = 0;
delete [] m->note;
// free(m->note);
}
/*
* This parses a given character array into an m_song
* Format:
* <note_letter><[sharp]><octave>:<length>; . . .;
* Example (Super Mario Bros.):
* E3:8; E3:8; R:8; E3:8; R:8; C3:8; E3:4; G3:4; R:4; G2:4; R:4;
*
* Sharp notes are represented with the # symbol as shown below:
* C#:4;
*
* song - The song character array
* num - The number of characters in the array
*/
m_song music::parse(char* song, int num){
//Create a new song and initialize it
m_song out;
init_song(&out,num);
char curnote = ' '; // Note
int octave = 0; // Octave
int dur[] = {0,0}; // Duration
int flag = 0; // Complete flag
int sharp = 0; // Sharp flag
int inl = 1; // Index of dur[]
for (int i=0; i<num; i++){
switch(song[i]){
case 'A':
//A Note
curnote = 'A';
break;
case 'B':
//B Note
curnote = 'B';
break;
case 'C':
//C Note
curnote = 'C';
break;
case 'D':
//D Note
curnote = 'D';
break;
case 'E':
//E Note
curnote = 'E';
break;
case 'F':
//F Note
curnote = 'F';
break;
case 'G':
//G Note
curnote = 'G';
break;
case 'R':
//Rest
curnote = 'R';
break;
case '#':
//Sharp set
sharp = 1;
break;
case '0':
if (flag == 0){
//Octave set
octave = 0;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 0;
}
else{
//Set
dur[1] = 0;
inl=0;
}
}
break;
case '1':
if (flag == 0){
//Octave set
octave = 1;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 1;
}
else{
//Set
dur[1] = 1;
inl=0;
}
}
break;
case '2':
if (flag == 0){
//Octave set
octave = 2;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 2;
}
else{
//Set
dur[1] = 2;
inl=0;
}
}
break;
case '3':
if (flag == 0){
//Octave set
octave = 3;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 3;
}
else{
//Set
dur[1] = 3;
inl=0;
}
}
break;
case '4':
if (flag == 0){
//Octave set
octave = 4;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 4;
}
else{
//Set
dur[1] = 4;
inl=0;
}
}
break;
case '5':
if (flag == 0){
//Octave set
octave = 5;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 5;
}
else{
//Set
dur[1] = 5;
inl=0;
}
}
break;
case '6':
if (flag == 0){
//Octave set
octave = 6;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 6;
}
else{
//Set
dur[1] = 6;
inl=0;
}
}
break;
case '7':
if (flag == 0){
//Octave set
octave = 7;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 7;
}
else{
//Set
dur[1] = 7;
inl=0;
}
}
break;
case '8':
if (flag == 0){
//Octave set
octave = 8;
}
else {
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 8;
}
else{
//Set
dur[1] = 8;
inl=0;
}
}
break;
case '9':
if (flag == 1){
//Duration set
if (inl == 0){
//Shift
dur[0] = dur[1];
//Set
dur[1] = 9;
}
else{
//Set
dur[1] = 9;
inl=0;
}
}
break;
case ':':
flag = 1;
break;
case ';':
if (flag == 1){
//Calculate duration
int t1 = (dur[0])*10;
int t2 = dur[1];
int tst = t1+t2;
if (tst>0 && tst<=64 && curnote != ' '){
notes n;
//DEAD CODE: Will work when realloc is fixed
//Create a temporary checker
//music_note* tmpn; //= new music_note[out.len+1];
//Reallocate space for note
//tmpn = (music_note*) realloc(out.note, (out.len+1)*sizeof(music_note));
// if (tmpn == NULL){
// //Failed to allocate
// free(out.note);
// exit(1);
// }
// out.note = tmpn;
//Set frequency using lookup function
out.note[out.len].freq = n.get_freq(curnote, sharp, octave);
//Set duration
out.note[out.len].duration = tst;
//Increment current song size
out.len=out.len+1;
}
//Reset values
flag = 0;
sharp = 0;
dur[0] = 0;
dur[1] = 0;
curnote = ' ';
octave = 0;
inl = 1;
}
else{
//Default to quarter note:
}
break;
}
}
return out;
}
/*
* This plays a given song string at a given tempo
*
* song - The song character array
* tempo - The specified beats per minute
* num - The number of characters in the array
*/
void music::play(char* song, double tempo, int num){
double dl;
m_song msng = parse(song, num);
/* Play m_song */
for (int i=0; i<msng.len; i++){
// Output the frequency:
freq(msng.note[i].freq);
// Calculate delay:
dl = (60*4)/(tempo*(msng.note[i].duration));
// Wait for the note to be complete
wait(dl);
}
//Stop playing
freq(0);
//Deallocate song:
dal_song(&msng);
}