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Dependencies: USBHost USBHostXpad mbed-rtos mbed
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Speaker.h
- Committer:
- juliandekker
- Date:
- 2015-03-02
- Revision:
- 1:da390b3b1330
- Parent:
- 0:345f76c72b9a
File content as of revision 1:da390b3b1330:
class Speaker { public: Speaker(PinName pin) : _pin(pin) { // _pin(pin) means pass pin to the Speaker Constructor // precompute 64 sample points on one sine wave cycle // used for continuous sine wave output later for(int k=0; k<64; k++) { Analog_out_data[k] = int (65536.0 * ((1.0 + sin((float(k)/64.0*6.28318530717959)))/2.0)); // scale the sine wave to 16-bits - as needed for AnalogOut write_u16 arg } } // class method to play a note based on AnalogOut class void PlayNote(float frequency, float duration, float volume) { // scale samples using current volume level arg for(int k=0; k<64; k++) { Analog_scaled_data[k] = Analog_out_data[k] * volume; } // reset to start of sample array i=0; // turn on timer interrupts to start sine wave output Sample_Period.attach(this, &Speaker::Sample_timer_interrupt, 1.0/(frequency*64.0)); // play note for specified time wait(duration); // turns off timer interrupts Sample_Period.detach(); // sets output to mid range - analog zero this->_pin.write_u16(32768); } private: // sets up specified pin for analog using AnalogOut class AnalogOut _pin; // set up a timer to be used for sample rate interrupts Ticker Sample_Period; //variables used by interrupt routine and PlayNote volatile int i; short unsigned Analog_out_data[64]; short unsigned Analog_scaled_data[64]; // Interrupt routine // used to output next analog sample whenever a timer interrupt occurs void Sample_timer_interrupt(void) { // send next analog sample out to D to A this->_pin.write_u16(Analog_scaled_data[i]); // increment pointer and wrap around back to 0 at 64 i = (i+1) & 0x03F; } };