// Chapter 11 6811 C programs// Jonathan W. Valvano// This software accompanies the book,// Embedded Microcomputer Systems: Real Time Interfacing// published by Brooks Cole, 1999//  Program 11.1. Software used to test how many bits are really needed.void DACout8(unsigned int code){     DACout(code&0xFFF0);}   // ignore bottom 4 bitsvoid DACout10(unsigned int code){     DACout(code&0xFFFC);}  // ignore bottom 2 bits//  Program 11.2. Periodic interrupt used to create the analog output waveform.unsigned int wave(unsigned int t){float result,time;time=2*pi*((float)t)/1000.0; // integer t in msec into floating point time in secondsresult=2048.0+1000.0*cos(31.25*time)-500.0*sin(125.0*time);return (unsigned int) result;}// Program 11.3. Periodic interrupt used to create the analog output waveform.// MC68HC11A8#define Rate 2000#define OC5  0x08unsigned int Time;  // Inc every 1ms #pragma interrupt_handler TOC5handler()void TOC5handler(void){   TFLG1=OC5;      // Ack interrupt    TOC5=TOC5+Rate; // Executed every 1 ms   Time++;    DACout(wave(Time));}// Program 11.4. Simple data structure for the waveform.unsigned int I;  // incremented every 1msconst unsigned int wave[32]= {3048,2675,2472,2526,2755,2957,2931,2597,2048,1499,1165,1139,1341,1570,1624,1421,1048,714,624,863,1341,1846,2165,2206,2048,1890,1931,2250,2755,3233,3472,3382};// Program 11.5. Periodic interrupt used to create the analog output waveform.// MC68HC11A8#define Rate 2000#define OC5  0x08#pragma interrupt_handler TOC5handler()void TOC5handler(void){   TFLG1=OC5;      // Ack interrupt    TOC5=TOC5+Rate; // Executed every 1 ms   if((++I)==32) I=0;    DACout(wave[I]);}// Program 11.6. Data structure with time and value for the waveform.int I;  // incremented every 1msint J;  // index into these two tablesconst int t[10]= {0,2,6,10,14,18,22,25,30,32};  // time in msecconst int wave[10]={3048,2472,2931,1165,1624,624,2165,1890,3472,3048}; //last=first//  Program 11.7. Periodic interrupt used to create the analog output waveform.// MC68HC11A8#define Rate 2000#define OC5  0x08#pragma interrupt_handler TOC5handler()void TOC5handler(void){   TFLG1=OC5;      // Ack interrupt    TOC5=TOC5+Rate; // Executed every 1 ms   if((++I)==32) {I=0; J=0;}    if(I==t[J])      DACout(wave[J]);   else if (I==t[J+1]){      J++;      DACout(wave[J]);}   else      DACout(wave[J]+((wave[J+1]-wave[J])          *(I-t[J]))/(t[J+1]-t[J]));}// Program 11.8. Data structure with delta time and value for the waveform.unsigned int I;  // incremented every sampleconst unsigned int wave[32]= {   3048,2675,2472,2526,2817,2981,2800,2337,1901,1499,1165,1341,1570,1597,1337, 952,    662, 654, 863,1210,1605,1950,2202,2141,1955,1876,2057,2366,2755,3129,3442,3382};const unsigned int dt[32]= { // time increment in 500 ns cycles  2000,2000,2000,2500,2500,2000,2000,1500,1500,2000,4000,2000,2500,2000,2000,2000,  2000,1500,1500,1500,1500,2000,2500,2000,2000,2000,1500,1500,1500,2000,2500,2000};//   Program 11.9. Periodic interrupt used to create the analog output waveform.// MC68HC11A8#define OC5  0x08#pragma interrupt_handler TOC5handler()void TOC5handler(void){   TFLG1=OC5;      // Ack interrupt    if((++I)==32) I=0;    TOC5=TOC5+dt[I]; // variable rate   DACout(wave[I]);}// Program 11.10. Software implementation of a ramp A/D.unsigned int rampAD(void){ unsigned int DOUT; // guess    DOUT = 0;             // start at minimum, V0=-5.00 (offset binary)    do {      DACout(DOUT);       // set D/A output, V0      DOUT++;             // ramp    }    while((!Z())&&(DOUT<4096));  // stop when V0>Vin or DOUT=4096    return(DOUT);}// Program 11.11. Software implementation of a tracking A/D.int DOUT; // guessvoid main(void){     DOUT = 2048;        // start in the middle, V0=0.00 (offset binary)    while(1) {      DACout(DOUT);     // set D/A output, V0      if(Z()) {         // check input        if(DOUT>0)      // don't go below 0           DOUT--;      // V0>Vin so decrement      }      else {        if(DOUT<4095)            DOUT++;      // V0<Vin so increment      }    }}// Program 11.12. Interrupting software implementation of a tracking A/D.#pragma interrupt_handler TOC5handler()void TOC5handler(void){   TFLG1=OC5;         // ack C5F    TC5=TC5+rate;    DACout(DOUT);      // set D/A output, V0   if(Z()) {          // check input      if(DOUT>0)      // don't go below 0         DOUT--;      // V0>Vin so decrement   }   else {      if(DOUT<4095)          DOUT++;      // V0<Vin so increment   }   DACout(DOUT);      // set D/A output, V0}// Program 11.13. Software implementation of a successive approximation A/D.unsigned int SuccAproxAD(void){ unsigned int DOUT,bit;     DOUT = 0;            for(bit=2048;bit;bit>>1){      DOUT |= bit;        // try to turn on this bit      DACout(DOUT);       // set D/A output, V0      if(Z())        DOUT ^= bit;      // too big, so remove this bit    }    return(DOUT);}   }}// Program 11.14. Software implementation of a sigma-delta A/D.unsigned char DOUT; // 8-bit sampleunsigned char SUM;  // number of times Z=0 and V0=1unsigned char CNT;  // 8-bit counter#pragma interrupt_handler TOC5handler()void TOC5handler(void){   TFLG1=OC5;        // ack C5F    TC5=TC5+rate;     // interrupt 256 times faster than the A/D output rate   if(Z())           // check input      DACout(0);     // too high, set D/A output, V0=0   else {      DACout(1);     // too low, set D/A output, V0=+5v      SUM++;   }   if(++CNT==0){     // end of 256 loops?      DOUT=SUM;      // new sample      SUM=0;         // get ready for the next   }}//  Program 11.15. Software implementation of first derivative using a multiple access circular queue.// MC68HC11A8#define Rate 2000#define OC5  0x08unsigned int x[4];  // MACQ (mV)unsigned int d;     // derivative (V/s)#pragma interrupt_handler TOC5handler()void TOC5handler(void){   TFLG1=OC5;      // Ack interrupt    TOC5=TOC5+Rate; // Executed every 1 ms   x[3]=x[2];  // shift MACQ data   x[2]=x[1];  // units of mV   x[1]=x[0];   x[0]=Adin(); // current data   d=x[0]+3*x[1]-3*x[2]-x[3];} // mV/msvoid ritual(void) { asm(" sei");    // make atomic   TMSK1|=OC5;  // Arm output compare 5   TFLG1=OC5;  // Initially clear OC5F   TOC5=TCNT+Rate; // First one in 1 msasm(" cli"); }//  Program 11.18. Assembly software to sample data using the A/D.// MC68HC11A8       void Init(void){   OPTION = 0x80;}  // Activate A/D #define CCF 0x80unsigned char A2D(unsigned char chan){    ADCTL=chan;    // Start A/D     while ((ADCTL & CCF) == 0){};    return(ADR1); }