YongChing Tee / Mbed 2 deprecated Lab3

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Dependencies:   FatFileSystem RPG TextLCD mbed wave_player

Speaker.h@1:ebb980d204ae, 2013-03-06 (annotated)

Committer:
YongChingTee
Date:
Wed Mar 06 00:21:35 2013 +0000
Revision:
1:ebb980d204ae
Parent:
0:ad48675db853 
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UserRevisionLine numberNew contents of line
YongChingTee 0:ad48675db853 1 class Speaker
YongChingTee 0:ad48675db853 2 {
YongChingTee 0:ad48675db853 3 public:
YongChingTee 0:ad48675db853 4 Speaker(PinName pin) : _pin(pin) {
YongChingTee 0:ad48675db853 5 // _pin(pin) means pass pin to the Speaker Constructor
YongChingTee 0:ad48675db853 6 // precompute 32 sample points on one sine wave cycle
YongChingTee 0:ad48675db853 7 // used for continuous sine wave output later
YongChingTee 0:ad48675db853 8 for(int k=0; k<32; k++) {
YongChingTee 0:ad48675db853 9 Analog_out_data[k] = int (65536.0 * ((1.0 + sin((float(k)/32.0*6.28318530717959)))/2.0));
YongChingTee 0:ad48675db853 10 // scale the sine wave to 16-bits - as needed for AnalogOut write_u16 arg
YongChingTee 0:ad48675db853 11 }
YongChingTee 0:ad48675db853 12
YongChingTee 0:ad48675db853 13 }
YongChingTee 0:ad48675db853 14 // class method to play a note based on AnalogOut class
YongChingTee 0:ad48675db853 15 void PlayNote(float frequency, float duration, float volume) {
YongChingTee 0:ad48675db853 16 // scale samples using current volume level arg
YongChingTee 0:ad48675db853 17 for(int k=0; k<32; k++) {
YongChingTee 0:ad48675db853 18 Analog_scaled_data[k] = Analog_out_data[k] * volume;
YongChingTee 0:ad48675db853 19 }
YongChingTee 0:ad48675db853 20 // reset to start of sample array
YongChingTee 0:ad48675db853 21 i=0;
YongChingTee 0:ad48675db853 22 // turn on timer interrupts to start sine wave output
YongChingTee 0:ad48675db853 23 Sample_Period.attach(this, &Speaker::Sample_timer_interrupt, 1.0/(frequency*32.0));
YongChingTee 0:ad48675db853 24 // play note for specified time
YongChingTee 0:ad48675db853 25 wait(duration);
YongChingTee 0:ad48675db853 26 // turns off timer interrupts
YongChingTee 0:ad48675db853 27 Sample_Period.detach();
YongChingTee 0:ad48675db853 28 // sets output to mid range - analog zero
YongChingTee 0:ad48675db853 29 this->_pin.write_u16(32768);
YongChingTee 0:ad48675db853 30
YongChingTee 0:ad48675db853 31 }
YongChingTee 0:ad48675db853 32 private:
YongChingTee 0:ad48675db853 33 // sets up specified pin for analog using AnalogOut class
YongChingTee 0:ad48675db853 34 AnalogOut _pin;
YongChingTee 0:ad48675db853 35 // set up a timer to be used for sample rate interrupts
YongChingTee 0:ad48675db853 36 Ticker Sample_Period;
YongChingTee 0:ad48675db853 37
YongChingTee 0:ad48675db853 38 //variables used by interrupt routine and PlayNote
YongChingTee 0:ad48675db853 39 volatile int i;
YongChingTee 0:ad48675db853 40 short unsigned Analog_out_data[32];
YongChingTee 0:ad48675db853 41 short unsigned Analog_scaled_data[32];
YongChingTee 0:ad48675db853 42
YongChingTee 0:ad48675db853 43 // Interrupt routine
YongChingTee 0:ad48675db853 44 // used to output next analog sample whenever a timer interrupt occurs
YongChingTee 0:ad48675db853 45 void Sample_timer_interrupt(void) {
YongChingTee 0:ad48675db853 46 // send next analog sample out to D to A
YongChingTee 0:ad48675db853 47 this->_pin.write_u16(Analog_scaled_data[i]);
YongChingTee 0:ad48675db853 48 // increment pointer and wrap around back to 0 at 32
YongChingTee 0:ad48675db853 49 i = (i+1) & 0x01F;
YongChingTee 0:ad48675db853 50 }
YongChingTee 0:ad48675db853 51 };
YongChingTee 0:ad48675db853 52