laowai_t.c

一段经典的老外编的SPWM程序

/***************************************************************************** 
* Filename: MAIN.C 
****************************************************************************** 
* 
* Author: Dave Karipides 
* Company: APS, Inc. 
* Date: 3-3-97 
* Compiled Using MPLAB-C Rev 1.21 
*       编译平台：MAPLAB-C Rev1.21（我用HT-PICC9.05L） 
****************************************************************************** 

****************************************************************************** 
* 
* Description: The main routine calls all the functions for generating 
* an OPEN_LOOP or FEEDBACK sine wave of either 50 or 60 Hz. 
*       软件描述：主程序调用函数产生开环和闭环调节的正弦波可设置50HZ或60HZ   
*******************************************************************************/ 
* 

/******************************************************************************
* 一些搜集的说明：	by CK.060809
*1	SPWM算法
*		根据取点公式V=VP*sine(2π*k/N); N 取点个数,K=0,1,2...,N-1,VP倍率系数。
*		本例中取N=255(8位),得到pwmtab[32]的数值。
*2	关于y = yold + (0.09261 * (x + xold)) ，它是PID的一个简化算法。
*		另有PID公式如下：Ui = U(i-1) + a0*e(i) - a1*e(i-1) + a2*e(i-2)
*		e为反馈值与设定值的偏差;
*		a为PID的具体参数 a0=Kp*(1+TD/TI+TD/T), a1=Kp*(1+2TD/T), a2=Kp*TD/T Kp, TD/TI/T分别为PID设定的参数

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

/***************************************************************************** 
* main() 
* 
* Description: The main routine initializes the registers and loops 
* forever.  All control is handled in the TMR0 INT 
* routine. 
*       主程序描述：主程序初始化个积存器组后台循环。所有控制操作在TMRO中断子程序处理。 
* 
* Input Variables: NONE 
*       输入变量：没有 
* Output Variables: NONE 
*       输出变量：没有 
* 
******************************************************************************/ 

//#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 最大额定电压输入表，测试用 
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 调节电压输入表 
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声明A/D采样函数 

unsigned char index; // Index into the sinewave reference table查表顺序寄存器 
unsigned char sign; // Flag used to unfold sinewave reference table正弦表输出标志 
long reference; // Value of the sinewave refrence after unfolding输出电压参考值 
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把电压的低位字节定义在电压寄存器的低位字节 
long out_volt; // Magnitude of the output voltage;输出电压大小 
long y; // Variables used in compensation routine；电压补偿子程序所用的变量 
long yold; 
long x; 
long xold; 
long ad_value; // A/D Converter Value；AD转换数值寄存器 

void main(void) 
{ 
CLRWDT();//清看门狗，一般PIC初始化之前需要加次命令，以免不必要的中断 
PORTC = 0; // Zero out portc latches；C端口积存器清零 
DDRC = 0x22; // Set up Data direction register for C；PORTC端口方向积存器定义 
DDRB = 0; // Set up Data direction register for B；PORTB端口方向积存器定义 
PR1 = 0xFF; // Setup PR1 register (24.4Khz @ 25Mhz clk)设置PWM频率在25MHZ时，PR1=0XFF，则PWM频率为24.4KHZ。具体计算见手册 
PW1DCL = 0; // Set low bits of PWM to 0 
PW1DCH = 0; // Init PWM duty cycle to 0；初始化占空比为零 

T0STA = 0x20; // Configure Timer0 prescaler；设置定时期T0预分频 
INTSTA.T0IE = 1; // Enable Timer 0 interrupt；开定时器TO中断 
TCON1.TMR1CS = 0; 
TCON1.T16 = 0; 
TCON2.TMR1ON = 1; // Start timer 1 (PWM timer)；开定时器T1 
TCON2.PWM1ON = 1; // Turn on the PWM，开定TMR2，PWM输出 
CPUSTA.GLINTD = 0; // Unmask the interrupts；开所有中断 

index = 0; // Initialize variables；个变量初始化 
sign = 0; 
y = 0; 
yold = 0; 
x = 0; 
xold = 0; 
PORTC.0 = 1; // Enable the Inverter；PORTC.0逆变允许开关，允许输出 
while(1); // Loop forever, execute in INT Routine；前台循环等待中断....... 
} 

#ifdef FEEDBACK//预编译命令，反馈闭环情况下TMRO中断处理。 
__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 
                                         TMRO每0.26ms中断一次，0.26*32=8.333...ms，为60HZ半周 
#ifdef 50Hz 
TMR0L=0x5F; // Make Timer0 interrupt at 3.20KHz for 50Hz output 
TMR0H=0xF8;                      TMR0每0。3125ms中断一次，0。3125*32=10ms，为50HZ半周 
#endif 
T0STA.T0CS = 1; // Start timer开定时器件 
CLRWDT();//清看门狗，防止死机 

reference = 0; // Clear Reference Value清除参考电压 
reference_lo = pwmtab[index]; // Lookup the value of the sinewave reference；查表,得到标准参考电压表数据，用于采样比较 

if (!index) // Toggle Sign Every Cycle Through table；每一次查表循环完毕标志取反，用以确定正负半周波形 
sign = ~sign; 
++index; // Increment index;正弦表顺序取值 
if (index == 32) // If end of table, reset counter；32个点查完后清index 
index = 0; 
if (sign) // If negative going wave；假如正输出负半周波形 
{ 
reference = ~reference; // V1.21 of Compiler negate (-ref) doesn't work for 
reference = reference + 1;// ref<=0 ；C编译器版本不同此运算不同 
} 
ad_value = read_ad(0);采样RA0端口数值，也即32个中断采样输出电压，就是半周取32个电压输出点。 
out_volt = ad_value - 512; // Read output voltage (512 counts=0 volts out)采样输出电压在512=0。 

// Form the expression y = yold + (0.09261 * (x + xold))；根据PID简化公式稳定调节输出电压 
// Where yold, xold is the value of y, x from the previous sample；yold,xold为前次采样到的y，x值 
// x is the , formed by the difference between the output；X为偏差信号，由输出电压波动数值和参考电压的差值来确定 
// of the inverter and the reference signal. 
x = out_volt - reference;//x等于当前输出电压（有AD采样得到）减取参考电压 
y = ((x + xold) * 24);// 
y = y / 256;//即简化计算0.09261 * (x + xold) 
y = y + yold;//逼近 
if (y >= 0) 
{ 
PORTC.2 = 0; // Set positive going cycle；控制正半周输出 
} else 
{ 
PORTC.2 = 1; // Set negative going cycle；控制负半周输出 
y = ~y; 
y = y + 1; 
} 
if (y > 255) 
y = 255; // Limit y；限制Y最大数值，不限制会益处复位，输出电压数值波形重创。 
PW1DCH = y; // Update duty cycle更新 
xold = x; // Store previous sample's state保存当前采样数值 
yold = y; 
PORTB.7=0; 
} 
#endif 
//采用开环输出方案，一般作测试用 
#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)//读AD,CHIP 
{ 
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 
}