File content as of revision 18:4992aa537387:

#include "mbed.h"
#include "sintable.h"

AnalogOut outMono(PA_4);//Not labeled in the docs for the f401, but seems to be for all
//AnalogOut DAC1(PA_5);

AnalogIn inVol(PA_0);
AnalogIn inModAmt(PA_1);
//AnalogIn ADC2(PA_2);//these are the uart pins!!
//AnalogIn ADC3(PA_3);//these are the uart pins!!
//AnalogIn ADC4(PA_4);//we're using these for output
//AnalogIn ADC5(PA_5);//we're using these for output
AnalogIn inCarA(PA_6);
AnalogIn inCarD(PA_7);
//AnalogIn ADC8(PB_0);//lets leave the 2 we aren't using in a single port
//AnalogIn ADC9(PB_1);//that way we know there's not ADCs on one of them
AnalogIn inCarS(PC_0);
AnalogIn inCarR(PC_1);
AnalogIn inModA(PC_2);
AnalogIn inModD(PC_3);
AnalogIn inModS(PC_4);
AnalogIn inModR(PC_5);

//BusIn keyBank(PC_10, PC_11, PC_12, PC_13, PD_2, PH_1); old
BusIn keyBank(PH_1, PD_2, PC_13, PC_12, PC_11, PC_10);
BusOut bankSelect(PB_0, PB_1, PB_2, PB_3, PB_4, PB_5, PB_6, PB_7, PB_8);
BusIn numerator(PA_8, PA_9, PA_10, PA_11);
BusIn denominator(PA_12, PA_13, PA_14, PA_15);

//Serial pc(USBTX, USBRX);

Ticker synthesisClock;

#define numKeys 49

//constants
const int carrierIncrements[] = {214, 227, 240, 254, 270, 286, 303, 321, 340, 
    360, 381, 404, 428, 454, 481, 509, 540, 572, 606, 642, 680, 720, 763, 809, 
    857, 908, 962, 1019, 1080, 1144, 1212, 1284, 1360, 1441, 1527, 1618, 1714, 
    1816, 1924, 2039, 2160, 2288, 2424, 2568, 2721, 2883, 3055, 3236, 3429};
#define attackLimit 0xFFFF
#define U_PI 3.14159265358979
//non-constants
//Most of these will be recalculated or reset on every input cycle of the main
//  loop, as appropriate
int FMmult = 1;
int Volume = 0xffff;
int modVol = 0x2000;
int64_t keyboard = 0;
int64_t modattack = 0x1ffffffffffff;
int64_t carattack = 0x1ffffffffffff;
int carrierPhases[numKeys];
int modulatorPhases[numKeys];
int envelopeAmpsC[numKeys];
int envelopeAmpsM[numKeys];

//int testTone = 0;

int modA = 0xffff;
int modD = 0xffff;
int modS = 0;
int modR = 0xffff;
int carA = 0xffff;
int carD = 0xffff;
int carS = 0;
int carR = 0xffff;

int fastSin(const int phase){
    int index = (phase & 0x3ffc) >> 2;
    int subindex = phase & 0x3;
    int quadrant = (phase & 0xc000) >> 14;
    int sum = 0;
    switch (quadrant) {
        case 0:
            sum += (4 - subindex) * sinTable[index];
            sum += subindex * sinTable[index+1];
            break;
        case 1:
            sum += (4 - subindex) * sinTable[1+4095-index];
            sum += subindex * sinTable[4095-index];
            break;
        case 2:
            sum -= (4 - subindex) * sinTable[index];
            sum -= subindex * sinTable[index+1];        
            break;
        case 3:
            sum -= (4 - subindex) * sinTable[1+4095-index];
            sum -= subindex * sinTable[4095-index];
            break;
    }
    sum = sum >> 2;
    
    return sum;
}

void synthesize(){
    int wave = 0;
    int subsignal;
    int64_t keymask;
    
    //testTone = testTone + carrierIncrements[25] & 0xffff;
    
    for(int64_t i = 0; i < numKeys; ++i){
        keymask = 1ll << i;
                
        if(!(keymask & keyboard)){
            carattack |= keymask;
            modattack |= keymask;
            
            if(envelopeAmpsC[i] > 0){
                envelopeAmpsC[i] -= carR;
            }
            if(envelopeAmpsM[i] > 0){
                envelopeAmpsM[i] -= modR;
            }
        }else{
            if(envelopeAmpsC[i] <= 0){
                carrierPhases[i] = 0;
                modulatorPhases[i] = 0;
                envelopeAmpsM[i] = 0;
            }
            
            if(keymask & carattack){
                if(envelopeAmpsC[i] < attackLimit ){
                    envelopeAmpsC[i] += carA;
                }else{
                    envelopeAmpsC[i] = attackLimit;
                    carattack &= ~keymask;
                }
            }else{
                if(envelopeAmpsC[i] > carS){
                    envelopeAmpsC[i] -= carD;
                }
            }
            
            if(keymask & modattack){
                if(envelopeAmpsM[i] < attackLimit){
                    envelopeAmpsM[i] += modA;
                }else{
                    envelopeAmpsM[i] = attackLimit;
                    modattack &= ~keymask;
                }
            }else{
                if(envelopeAmpsM[i] > modS){
                    envelopeAmpsM[i] -= modD;
                }
            }
            
            if(envelopeAmpsC[i] > 0){
                modulatorPhases[i] += (carrierIncrements[i] * FMmult)>> 16;
                int modulation = (fastSin(modulatorPhases[i]) * envelopeAmpsM[i])>>16;
                modulation = (modulation * modVol) >> 16;
                carrierPhases[i] += carrierIncrements[i] + modulation;
                subsignal = (fastSin(carrierPhases[i]) * envelopeAmpsC[i])>>16;
                wave += subsignal >> 3;
            }
        }
        
    }
    //if(keyboard)
    //    wave += fastSin(testTone);
    
    wave = wave * Volume >> 16;
    //wave = wave << 3;

    wave = (wave > 32767) ? 32767 : wave;
    wave = (wave < -32768) ? - 32768 : wave;
    wave += 32768;
    outMono.write_u16(wave);
}


int main() {
    int ratNumer;
    int ratDenom;    
    int64_t keytemp;
    int tempCarA, tempCarD, tempCarR, tempModA, tempModD, tempModR;

    for(int i = 0; i < numKeys; ++i){
        carrierPhases[i] = 0;
        modulatorPhases[i] = 0;
        envelopeAmpsC[i] = 0;
        envelopeAmpsM[i] = 0;
    }
    
    keyBank.mode(PullNone);
    synthesisClock.attach(synthesize, 0.00005);//debug
    
    //pc.printf("done.\r\n");
    while(true){
        ratNumer = 0xf & ~ numerator;
        ratDenom = 0xf & ~ denominator;
        FMmult = (ratNumer << 16) / ratDenom;
        
        Volume = (int)inVol.read_u16();
        
        modVol = (int)inModAmt.read_u16();
        
        tempCarA = inCarA.read_u16();
        if(! tempCarA)
            carA = 0xffff;
        else
            carA = 0xffff / tempCarA;
        
        tempCarD = inCarD.read_u16();
        if(! tempCarD)
            carD = 0xffff;
        else
            carD = 0xffff / tempCarD;
        
        carS = (int)inCarS.read_u16();
        
        tempCarR = inCarR.read_u16();
        if(! tempCarR)
            carR = 0xffff;
        else
            carR = 0xffff / tempCarR;
        
        tempModA = inModA.read_u16();
        if(! tempModA)
            modA = 0xffff;
        else
            modA = 0xffff / tempModA;
        
        tempModD = inModD.read_u16();
        if(! tempModD)
            modD = 0xffff;
        else
            modD = 0xffff / tempModD;
        
        modS = (int)inModS.read_u16();
        
        tempModR = inModR.read_u16();
        if(! tempModR)
            modR = 0xffff;
        else
            modR = 0xffff / tempModR;
        
        keytemp = 0; //zero the keys before we start ORing on top of everything
        for(int i = 0; i < 9; ++i) {
            bankSelect = (~(1 << i)) & bankSelect.mask();
            wait_us(40);
            int shiftOffset = 6LL * i;
            
            keytemp |= ((~(unsigned long long)keyBank) & (unsigned long long)keyBank.mask()) << (unsigned long long)shiftOffset;
        }
        keytemp >>= 5;
        
        keyboard = keytemp;
        
        wait_ms(10);
    }
}