***************************************************************************** 
* Filename: MAIN.C 
****************************************************************************** 
* 
* Author: Dave Karipides 
* Company: APS, Inc. 
* Date: 3-3-97 
* Compiled Using MPLAB-C Rev 1.21 
* 
****************************************************************************** 

****************************************************************************** 
* 
* Description: The main routine calls all the functions for generating 
* an OPEN_LOOP or FEEDBACK sine wave of either 50 or 60 Hz. 
* 
****************************************************************************** 
* 

* 
* 
******************************************************************************/ 

/***************************************************************************** 
* main() 
* 
* Description: The main routine initializes the registers and loops 
* forever.  All control is handled in the TMR0 INT 
* routine. 
* 
* 
* Input Variables: NONE 
* 
* Output Variables: NONE 
* 
* 
******************************************************************************/ 

//#define OPEN_LOOP 
#define FEEDBACK 
//#define 50Hz 
#define 60Hz 

#pragma option v 
#include <17c43.h> 
#include 
#include 

#ifdef OPEN_LOOP 
// This table yields Full VRMS input 
unsigned char const pwmtab[32]={0,25,50,74,98,120,142,162,180,197,212, 
225,235,244,250,254,255,254,250,244,235, 
225,212,197,180,162,142,120,98,74,50,25}; 
#endif 
#ifdef FEEDBACK 
// This table yields slightly less than Full VRMS input 
unsigned char const pwmtab[32]={0,20,40,60,79,97,114,131,145,159,171, 
181,189,197,202,205,206,205,202,197,189, 
181,171,159,145,131,114,97,79,60,40,20}; 
#endif 

long read_ad(unsigned char); // Prototype for A/D converter function 

unsigned char index; // Index into the sinewave reference table 
unsigned char sign; // Flag used to unfold sinewave reference table 
long reference; // Value of the sinewave refrence after unfolding 
unsigned char reference_lo  @ reference; // V1.21 of Compiler does not type cast unsigned 
// char to long so we will write to low byte separately 
long out_volt; // Magnitude of the output voltage; 
long y; // Variables used in compensation routine 
long yold; 
long x; 
long xold; 
long ad_value; // A/D Converter Value 

void main(void) 
{ 
CLRWDT(); 
PORTC = 0; // Zero out portc latches 
DDRC = 0x22; // Set up Data direction register for C 
DDRB = 0; // Set up Data direction register for B 
PR1 = 0xFF; // Setup PR1 register (24.4Khz @ 25Mhz clk) 
PW1DCL = 0; // Set low bits of PWM to 0 
PW1DCH = 0; // Init PWM duty cycle to 0 

T0STA = 0x20; // Configure Timer0 prescaler 
INTSTA.T0IE = 1; // Enable Timer 0 interrupt 
TCON1.TMR1CS = 0; 
TCON1.T16 = 0; 
TCON2.TMR1ON = 1; // Start timer 1 (PWM timer) 
TCON2.PWM1ON = 1; // Turn on the PWM 
CPUSTA.GLINTD = 0; // Unmask the interrupts 

index = 0; // Initialize variables 
sign = 0; 
y = 0; 
yold = 0; 
x = 0; 
xold = 0; 
PORTC.0 = 1; // Enable the Inverter 
while(1); // Loop forever, execute in INT Routine 
} 

#ifdef FEEDBACK 
__TMR0() // Timer  interrupt 
{ 
T0STA.T0CS = 0; // Stop timer 
PORTB.7=1; 
#ifdef 60Hz 
TMR0L=0xA5; 
TMR0H=0xF9; // Make Timer0 interrupt at 3.84KHz for 60Hz output 
#endif 
#ifdef 50Hz 
TMR0L=0x5F; // Make Timer0 interrupt at 3.20KHz for 50Hz output 
TMR0H=0xF8; 
#endif 
T0STA.T0CS = 1; // Start timer 
CLRWDT(); 

reference = 0; // Clear Reference Value 
reference_lo = pwmtab[index]; // Lookup the value of the sinewave reference 

if (!index) // Toggle Sign Every Cycle Through table 
sign = ~sign; 
++index; // Increment index 
if (index == 32) // If end of table, reset counter 
index = 0; 
if (sign) // If negative going wave 
{ 
reference = ~reference; // V1.21 of Compiler negate (-ref) doesn't work for 
reference = reference + 1;// ref<=0 
} 
ad_value = read_ad(0); 
out_volt = ad_value - 512; // Read output voltage (512 counts=0 volts out) 

// Form the expression y = yold + (0.09261 * (x + xold)) 
// Where yold, xold is the value of y, x from the previous sample 
// x is the , formed by the difference between the output 
// of the inverter and the reference signal. 
x = out_volt - reference; 
y = ((x + xold) * 24); 
y = y / 256; 
y = y + yold; 
if (y >= 0) 
{ 
PORTC.2 = 0; // Set positive going cycle 
} else 
{ 
PORTC.2 = 1; // Set negative going cycle 
y = ~y; 
y = y + 1; 
} 
if (y > 255) 
y = 255; // Limit y 
PW1DCH = y; // Update duty cycle 
xold = x; // Store previous sample's state 
yold = y; 
PORTB.7=0; 
} 
#endif 

#ifdef OPEN_LOOP 
// The inverter runs in an open loop mode with OPEN_LOOP defined. 
__TMR0() // Timer interrupt 
{ 
T0STA.T0CS = 0; // Stop timer 
#ifdef 60Hz 
TMR0L=0xA5; 
TMR0H=0xF9; //Make Timer0 interrupt at 3.84KHz for 60Hz output 
#endif 
#ifdef 50Hz 
TMR0L=0x5F; //Make Timer0 interrupt at 3.20KHz for 50Hz output 
TMR0H=0xF8; 
#endif 
T0STA.T0CS=1; //Start timer 
CLRWDT(); 

PW1DCH = pwmtab[index]; 
if (!index) 
{ 
PORTC.0 = 0; // Gate Drive off 
PORTC.2 = ~PORTC.2; // Flip Pos/Neg bit 
PORTC.0 = 1; // Gate Drive on 
} 
++index; 
if (index == 32) 
index = 0; 
PORTC.3 = ~PORTC.3; // Toggle bit to test freq. 
} 
#endif 

long read_ad(unsigned char channel) 
{ 
long result; 

PORTC.6 = 1; // Write bit high 
PORTC.7 = 1; // Read bit high 
PORTC.4 = 1; // Chip select high 
DDRD = 0; // Make PORTD an output 
PORTD = 0x04; // Single ended mode signed 10 bit chan 0 Right justified 
PORTC.4 = 0; // Select chip 
PORTC.6 = 0; // latch command word int A/D 
PORTC.6 = 1; // Start conversion 
PORTC.4 = 1; // Deselect chip 
while (PORTC.5); // Wait for conversion to complete 
DDRD = 0xFF; // Make PORTD an input 
PORTC.4 = 0; // Select chip 
PORTC.7 = 0; // Read high byte 
*( ((unsigned char*)&result) + 1) = PORTD; 
PORTC.7 = 1; 
PORTC.4 = 1; 
PORTC.4 = 0; 
PORTC.7 = 0; // Read low byte 
*( ((unsigned char*)&result) ) = PORTD; 
PORTC.7 = 1; 
PORTC.4 = 1; // Reset chip select lines 
return (result); // Return data 
}