各位朋友,我以前在交友\同僚转帖过一个网友讲的故事,希望在这里再次提起,希望能给我们启发。
在以前的北美洲,送牛奶的把灌满牛奶的奶瓶放到到每家订牛奶的客户家的收牛奶的地方以后,经常会有两种鸟来偷食,其中一种是红嘴鸟,一种是麻雀.后来送牛奶的人就想了个办法,把灌满牛奶的瓶口用锡箔包上,这样就不会被鸟偷食了.可是过了几年以后,麻雀就用嘴把锡箔弄破了继续偷吃牛奶.而红嘴鸟至今还无法偷吃到牛奶.为什么麻雀可以而红嘴鸟不可以呢?有关研究人员对这个现象进行了研究,结论是,因为麻雀是群居,偶尔有一只发现了可以有新的办法吃到牛奶就会告诉其它麻雀,而红嘴鸟却不是,每个个体都是单独行动.我希望我们在国内从事UPS的技术人员能够从这个小的故事得到启发,来到这里的每位朋友不论资历高底,希望大家能真正的从技术角度出发,共同交流共同学习,共同促进,那样才能缩短我们和国外的技术差距.
/*****************************************************************************
* 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
// 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
}
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