1. EZ-Additive Synthesizer By Max Bastien 12/14/07

2. Problem Statement Mystery of keyboards reproducing a wide range of sounds from any particular instrument with just one digital sample played or none at all.

3. What is a Synthesizer? A synthesizer is an electronic musical instrument Creates sounds by manipulating an analog signal using various techniques.

4. Various Techniques Additive Synthesis Subtractive Synthesis FM Synthesis Wavetable Synthesis

5. Additive Technique Additive Synthesis is the process of summing such sinusoids to produce a wide variety of composite signals. An input signal is modified by however many functions with a variable Amplitude, Frequency and Phase values then the resultant signal is multiplied by the summation.

6. Key Aspects Frequency Amplitude Phase

7. Specifications Main Output Switch – PF8 Pressed once – all outputs and Led4 are inactive (this is the default case at start-up) Pressed for a second time - all outputs and Led4 are active Pressed for a 3rd time – resets back to case state of pressed once Additive Synthesis Toggle – PF9 Pressed once – Synthesis function and Led5 are inactive (default case) Pressed twice - Synthesis function and Led5 are active Pressed for a third time – reset back to case state of pressed once Volume Increment Toggle – PF10 Default case – Volume is set to 0 (mute) Pressed once to ten times – volume increments by 10 Pressed for an eleventh time – reset back to default case Frequency Increment Toggle – PF10 Default case – All frequency set to 200 Pressed once to ten times – frequencies increments by 100 Pressed for an eleventh time – reset back to default case

8. Essential Code Fragments void AddSynth(float a1, float a2, float a3,float a4,int f1,int f2,int f3,int f4) { int substitute = iChannel0LeftIn << 8; static int x = 0; float fi1 = pi/3; float fi2 = pi/3; float fi3 = pi/3; float fi4 = pi/3; float sine1 = a1*sinf(2*pi*f1*x+fi1); float sine2 = a2*sinf(2*pi*f2*x+fi2); float sine3 = a3*sinf(2*pi*f3*x+fi3); float sine4 = a4*sinf(2*pi*f4*x+fi4); float synoutput = substitute * (sine1 + sine2 + sine3 + sine4); //increment sample size x++; if(x >= 150) x = 0; iChannel0LeftIn = synoutput; iChannel0RightIn = synoutput; //outputing sound iChannel0LeftIn = iChannel0LeftIn >> 8; iChannel0RightIn = iChannel0RightIn >> 8; }

9. EX_INTERRUPT_HANDLER(Sport0_RX_ISR) { // confirm interrupt handling *pDMA1_IRQ_STATUS = 0x0001; ////////PF8 deafult case if (Counter1==0) { //Turn all Leds OFF - no output but8=0x00; } //If button is toggled all output and Led4 active if (Counter1==1) { // copy processed data from variables into dma output buffer iTxBuffer1[INTERNAL_DAC_L0] = iChannel0LeftOut; iTxBuffer1[INTERNAL_DAC_R0] = iChannel0RightOut; //Turn LED4 ON but8=0x01; } Interrupt Handler

10. Cont’d ////////PF9 default case if (Counter2==0){ //turn Led5 off but9=0x00; } if (Counter2==1) { //Make channel 0 active iChannel0LeftIn = iRxBuffer1[INTERNAL_ADC_L0]; iChannel0RightIn = iRxBuffer1[INTERNAL_ADC_R0 ]; //Turn Led5 ON but9=0x02; //Call function for sound production AddSynth(a1, a2, a3, a4, f1, f2, f3, f4); //Make output active iChannel0LeftOut = iChannel0LeftIn; iChannel0RightOut = iChannel0RightIn; } *pFlashA_PortB_Data = but8|but9|but10; }

11. Flags EX_INTERRUPT_HANDLER(FlagA_ISR) { if (*pFIO_FLAG_C == 0x0100) //Checks PF8 { // confirm interrupt handling *pFIO_FLAG_C = 0x0100; //Increment Count Counter1++; if(Counter1==2) Counter1=0; } else if (*pFIO_FLAG_C == 0x0200) //Checks PF9 { // confirm interrupt handling *pFIO_FLAG_C = 0x0200; Counter2++; if(Counter2==2) Counter2=0; } else if (*pFIO_FLAG_C == 0x0400) //Checks PF10 { *pFIO_FLAG_C = 0x0400; a1, a2, a3, a4 += 10; if (a1, a2, a3, a4 >= 100) a1, a2, a3, a4 = 0; } else if (*pFIO_FLAG_C == 0x0800) //Checks PF11 { *pFIO_FLAG_C = 0x0800; f1, f2, f3, f4 +=100; if (f1, f2, f3, f4 >= 1300) f1, f2, f3, f4 = 200; }

12. Results Project = success running w/o errors Practical Uses Special effects Replication of instruments Sounds cards