![](/media/cache/group/default_image.jpg.50x50_q85.jpg)
Drive a speaker using PWM
Dependencies: mbed
Dependents: PwmSpeaker-Example
Speaker.cpp
- Committer:
- asmellby
- Date:
- 2015-11-12
- Revision:
- 0:b7dd35e61bb1
- Child:
- 1:10005e388826
File content as of revision 0:b7dd35e61bb1:
#include "Speaker.h" static int notes[] = {0, NOTE_C4, NOTE_CS4, NOTE_D4, NOTE_DS4, NOTE_E4, NOTE_F4, NOTE_FS4, NOTE_G4, NOTE_GS4, NOTE_A4, NOTE_AS4, NOTE_B4, NOTE_C5, NOTE_CS5, NOTE_D5, NOTE_DS5, NOTE_E5, NOTE_F5, NOTE_FS5, NOTE_G5, NOTE_GS5, NOTE_A5, NOTE_AS5, NOTE_B5, NOTE_C6, NOTE_CS6, NOTE_D6, NOTE_DS6, NOTE_E6, NOTE_F6, NOTE_FS6, NOTE_G6, NOTE_GS6, NOTE_A6, NOTE_AS6, NOTE_B6, NOTE_C7, NOTE_CS7, NOTE_D7, NOTE_DS7, NOTE_E7, NOTE_F7, NOTE_FS7, NOTE_G7, NOTE_GS7, NOTE_A7, NOTE_AS7, NOTE_B7 }; void Speaker::set_frequency(uint32_t frequency) { _pwm.period(1.0/frequency); } void Speaker::enable(bool enable) { *this = enable; } Speaker& Speaker::operator=(int setting) { if (setting) { _pwm = 0.5; } else { _pwm = 1; } return *this; } /* * Plays an old-school ringtone in RTTTL language. */ void Speaker::play_rtttl(char * p) { // Absolutely no error checking in here uint8_t default_dur = 4; uint8_t default_oct = 6; int bpm = 63; int num; long wholenote; long duration; uint8_t note; uint8_t scale; // format: d=N,o=N,b=NNN: // find the start (skip name, etc) while(*p != ':') p++; // ignore name p++; // skip ':' // get default duration if(*p == 'd') { p++; p++; // skip "d=" num = 0; while(isdigit(*p)) { num = (num * 10) + (*p++ - '0'); } if(num > 0) default_dur = num; p++; // skip comma } printf("ddur: %d\n", default_dur); // get default octave if(*p == 'o') { p++; p++; // skip "o=" num = *p++ - '0'; if(num >= 3 && num <=7) default_oct = num; p++; // skip comma } printf("doct: %d\n", default_oct); // get BPM if(*p == 'b') { p++; p++; // skip "b=" num = 0; while(isdigit(*p)) { num = (num * 10) + (*p++ - '0'); } bpm = num; p++; // skip colon } printf("bpm: %d\n",bpm); // BPM usually expresses the number of quarter notes per minute wholenote = (60 * 1000L / bpm) * 4; // this is the time for whole note (in milliseconds) printf("wn: %d\n", wholenote); // now begin note loop while(*p) { // first, get note duration, if available num = 0; while(isdigit(*p)) { num = (num * 10) + (*p++ - '0'); } if(num) duration = wholenote / num; else duration = wholenote / default_dur; // we will need to check if we are a dotted note after // now get the note note = 0; switch(*p) { case 'c': note = 1; break; case 'd': note = 3; break; case 'e': note = 5; break; case 'f': note = 6; break; case 'g': note = 8; break; case 'a': note = 10; break; case 'b': note = 12; break; case 'p': default: note = 0; } p++; // now, get optional '#' sharp if(*p == '#') { note++; p++; } // now, get optional '.' dotted note if(*p == '.') { duration += duration/2; p++; } // now, get scale if(isdigit(*p)) { scale = *p - '0'; p++; } else { scale = default_oct; } scale += _offset; if(*p == ',') p++; // skip comma for next note (or we may be at the end) // now play the note if(note) { //printf("\027\033H"); //printf("Playing: %d %d (%d) %d\n", scale, note, notes[(scale - 4) * 12 + note], duration); set_frequency(notes[(scale - 4) * 12 + note]); enable(true); wait_ms(duration); enable(false); } else { //printf("Pausing: %d\n", duration); wait_ms(duration); } } }