![](/media/cache/group/default_image.jpg.50x50_q85.jpg)
Drive a speaker using PWM
Dependencies: mbed
Dependents: PwmSpeaker-Example
Diff: Speaker.cpp
- Revision:
- 0:b7dd35e61bb1
- Child:
- 1:10005e388826
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Speaker.cpp Thu Nov 12 21:04:11 2015 +0000 @@ -0,0 +1,187 @@ +#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); + } + } +} \ No newline at end of file