Waveform Generation (Triangle Wave) C Program

Waveform Generation (Triangle Wave) C Program

How to write a Waveform Generation (Triangle Wave) program in C Programming Language ?


  1. /*
  2.  * main.c
  3.  *
  4.  * Title: Assignment 4 Waveform Generation (Triangle Wave)
  5.  *
  6.  * Authors: Daniel Hodges & Omar Arriaga
  7.  *
  8.  * Description: Interfaces with the MCP4921 DAC via SPI to generate
  9.  * a 2Vpp triangle wave with 1VDC offset and a period of 20ms using timers.
  10.  *
  11.  */
  13. #include <msp430g2553.h>
  15. void Drive_DAC(unsigned int level);
  17. int ISRcounter = 0;
  19. int main(void)
  20. {
  22.   WDTCTL = WDTPW + WDTHOLD;          // Stop watchdog timer
  24.   // 16Mhz SMCLK
  25.   if (CALBC1_16MHZ==0xFF)            // If calibration constant erased
  26.   {
  27.     while(1);                        // do not load, trap CPU!!
  28.   }
  29.   DCOCTL = 0;                        // Select lowest DCOx and MODx settings
  30.   BCSCTL1 = CALBC1_16MHZ;            // Set range
  31.   DCOCTL = CALDCO_16MHZ;             // Set DCO step + modulation
  33.   // Init Ports
  34.   P1DIR |= BIT4;                     // Will use BIT4 to activate /CE on the DAC
  36.   P1SEL  = BIT7 + BIT5;              // These two lines dedicate P1.7 and P1.5
  37.   P1SEL2 = BIT7 + BIT5;              // for UCB0SIMO and UCB0CLK respectively
  39.   // SPI Setup
  40.   // clock inactive state = low,
  41.   // MSB first, 8-bit SPI master,
  42.   // 4-pin active Low STE, synchronous
  43.   //
  44.   // 4-bit mode disabled for now
  45.   UCB0CTL0 |= UCCKPL + UCMSB + UCMST + /* UCMODE_2 */ + UCSYNC;
  47.   UCB0CTL1 |= UCSSEL_2;               // UCB0 will use SMCLK as the basis for
  48.                                       // the SPI bit clock
  50.   UCB0CTL1 &= ~UCSWRST;               // **Initialize USCI state machine**
  51.                                       // SPI now Waiting for something to
  52.                                       // be placed in TXBUF.
  54.   // set up SMCLK timer
  55.   CCTL0 = CCIE;                       // CCR0 interrupt enabled
  56.   CCR0 = 98;
  57.   TACTL = TASSEL_2 + MC_2;            // SMCLK, contmode
  59.   _enable_interrupts();               // enable interrupts
  61.   while(1){
  63.         // if statement determines when
  64.         // to increment/decrement DAC output
  65.         if (ISRcounter <= 1638){                        // increments DAC output from 0 to 2V
  66.                 Drive_DAC(ISRcounter);
  67.         }
  68.         else if(ISRcounter > 1638 & ISRcounter < 3276){ // decrements DAC output from 2 to 0V
  69.             Drive_DAC(3276-ISRcounter);
  70.         }
  71.         else{                                           // resets ISRcounter back to 0 to start over again
  72.                 ISRcounter = 0;
  73.                 Drive_DAC(ISRcounter);
  74.         }
  76.   }
  79. }
  81. // Drives DAC through SPI; takes value from 0 to 4096
  82. void Drive_DAC(unsigned int level){
  83.   unsigned int DAC_Word = 0;
  85.   DAC_Word = (0x3000) | (level & 0x0FFF);   // 0x3000 sets DAC for Write
  86.                                             // to DAC, Gain = 1, /SHDN = 1
  87.                                             // and put 12-bit level value
  88.                                             // in low 12 bits.
  90.   P1OUT &= ~BIT4;                           // Clear P1.4 (drive /CS low on DAC)
  91.                                             // Using a port output to do this for now
  93.   UCB0TXBUF = (DAC_Word >> 8);              // Shift upper byte of DAC_Word
  94.                                             // 8-bits to right
  96.   while (!(IFG2 & UCB0TXIFG));              // USCI_A0 TX buffer ready?
  98.   UCB0TXBUF = (unsigned char)
  99.                        (DAC_Word & 0x00FF); // Transmit lower byte to DAC
  101.   while (!(IFG2 & UCB0TXIFG));              // USCI_A0 TX buffer ready?
  103.   P1OUT |= BIT4;                            // Set P1.4   (drive /CS high on DAC)
  104.   return;
  105. }
  107. // Timer A0 interrupt service routine
  108. #pragma vector=TIMER0_A0_VECTOR
  109. __interrupt void Timer_A (void)
  110. {
  112.   ISRcounter++;   // Increment ISRcounter
  114.   CCR0 += 98;     // Extend timer by 6.125us
  116. }


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