Question

我试图用c语言定义一个二维数组并用float类型的变量初始化它但是我遇到了这个错误：

"must be constant expression"
这是我的代码：

/*******************************************************
This program was created by the
CodeWizardAVR V3.12 Advanced
Automatic Program Generator
© Copyright 1998-2014 Pavel Haiduc, HP InfoTech s.r.l.
http://www.hpinfotech.com

Project : 
Version : 
Date    : 1/30/2017
Author  : 
Company : 
Comments: 


Chip type               : ATmega8A
Program type            : Application
AVR Core Clock frequency: 8.000000 MHz
Memory model            : Small
External RAM size       : 0
Data Stack size         : 256
*******************************************************/

#include <mega8.h>
#include <stdio.h>
#include <delay.h>
#include <alcd.h>

#define A Hall_1
#define B Hall_2
#define C Hall_3


//...........................................................................................
// Declare your global variables here
float Hall_1 ,Hall_2 ,Hall_3 ;
int count=0;

//----------------------------------------------------------------------------------------------------

// Timer 0 overflow interrupt service routine
interrupt [TIM1_OVF] void timer1_ovf_isr(void)
{
count++;

}

//----------------------------------------------------------------------------------------------

// ADC interrupt service routine
interrupt [ADC_INT] void adc_isr(void)
{


}
//-----------------------------------------------------------------------------------------------

float adc_read(unsigned char);
float maxf(float , float , float);
float minf(float , float , float);
void commutate(unsigned char*);

//-----------------------------------------------------------------------------------------------

void main(void)
{
// Declare your local variables here

float comt_sequence[6][2]= {{B,A},{B,C},{A,C},{A,B},{C,B},{C,A}};
// Timer/Counter 0 initialization
// Clock source: System Clock
// Clock value: 8000.000 kHz
TCCR1B=(0<<CS02) | (0<<CS01) | (0<<CS00);
TCNT1=0x00;



// Timer(s)/Counter(s) Interrupt(s) initialization
TIMSK=(0<<OCIE2) | (0<<TOIE2) | (0<<TICIE1) | (0<<OCIE1A) | (0<<OCIE1B) | (0<<TOIE1) | (0<<TOIE0);

// External Interrupt(s) initialization
// INT0: Off
// INT1: Off
MCUCR=(0<<ISC11) | (0<<ISC10) | (0<<ISC01) | (0<<ISC00);


// ADC initialization
// ADC Clock frequency: 250.000 kHz
// ADC Voltage Reference: Int., cap. on AREF
// Only the 8 most significant bits of
// the AD conversion result are used
ADMUX= (1<<REFS1) | (1<<REFS0) | (1<<ADLAR) ;
ADCSRA=(1<<ADEN) | (0<<ADSC) | (0<<ADFR) | (0<<ADIF) | (0<<ADIE) | (1<<ADPS2) | (0<<ADPS1) | (1<<ADPS0);
SFIOR=(0<<ACME);

// Alphanumeric LCD initialization
// Connections are specified in the
// Project|Configure|C Compiler|Libraries|Alphanumeric LCD menu:
// RS - PORTD Bit 0
// RD - PORTD Bit 1
// EN - PORTD Bit 2
// D4 - PORTD Bit 4
// D5 - PORTB Bit 6
// D6 - PORTB Bit 7
// D7 - PORTD Bit 5
// Characters/line: 16
lcd_init(40);

// Global enable interrupts
#asm("sei")

lcd_putsf("start");
delay_ms(500);
lcd_clear();

while (1)
      { 

       unsigned char buffer[18] , s=0;
       float m,n=0 , max_min[2]; 
       TCCR1B=1; //start counting cycles
       Hall_1 = adc_read(5);
       Hall_2 = adc_read(4);
       Hall_3 = adc_read(3);

       m=maxf(Hall_1,Hall_2,Hall_3); 
       /*if(m == Hall_1) 
                    lcd_putsf("Max= A ");  
       else if(m == Hall_2)
                    lcd_putsf("Max= B ");
       else if(m == Hall_3)
                    lcd_putsf("Max= C ");
       else
            lcd_putsf("Error"); */

       n=minf(Hall_1,Hall_2,Hall_3);
       /*if(n == Hall_1) 
                    lcd_putsf("Min= A");  
       else if(n == Hall_2)
                    lcd_putsf("Min= B");
       else if(n == Hall_3)
                    lcd_putsf("Min= C");
       else
            lcd_putsf("Error");*/
       max_min[0] = m;
       max_min[1] = n;  

       s=count;
       sprintf(buffer,"%5.4f %5.4f %d",max_min[0],max_min[1] ,TCNT1);
       lcd_puts(buffer);    
       delay_ms(1000);
       lcd_clear();
      }
}



///////////////////////////////////////////////
float adc_read(unsigned char ch)
{

    unsigned char lcd_buff[18];
    float adc_data;
  // select the corresponding channel 0~7
  // ANDing with ’7' will always keep the value
  // of ‘ch’ between 0 and 5   ""ATmega8 has 6 ADC channel 0-5""
  ch &= 0b00000111;  // AND operation with 5
  ADMUX = (ADMUX & 0xF8)|ch; // clears the bottom 3 bits before ORing   

  // start single convertion
  // write ’1' to ADSC
  ADCSRA |= (1<<ADSC);

    // Wait for the AD conversion to complete
    while ((ADCSRA & 0x10)==0);
    ADCSRA|=0x10;

    // Read the 8 most significant bits
    // of the AD conversion result
    adc_data=(ADCH * 2.56)/255;
    //sprintf(lcd_buff," %5.3f ",adc_data);
    //lcd_puts(lcd_buff);
    //delay_ms(500);
    return adc_data;
}

//------------------------------------------------------------------------------------------------
float maxf(float a , float b , float c) {

float m;
m = (a>b)?a:b;
m = (m>c)?m:c;
return m;
}

float minf(float a , float b , float c) {

float m;
m = (a<b)?a:b;
m = (m<c)?m:c;
return m;
}

//--------------------------------------------------------------------------------------
void commutate(unsigned char *max_min){

unsigned char x=0, i=0;


//unsigned char comt_pattern[6][2] = {(
for (i=0; i<6 ;i++)
    if((max_min[0] == comt_sequence[i][0]) && (max_min[1] == comt_sequence[i][1])) x=i;
switch(x){
    case 0:
    break;
    case 1:
    break;
    case 2:
    break;
    case 3:
    break;
    case 4:
    break;
    case 5:
    break;
    }

}

我添加了我的整个代码，我还提到Hall变量保存了传感器的ADC读数，其值会定期更改，这是我的错吗？
请帮忙

Answer 1

您可能无法使用非常量初始化程序在C中初始化具有静态存储持续时间的数组。

从C标准（6.7.9初始化）

4具有静态的对象的初始值设定项中的所有表达式或线程存储持续时间应为常量表达式或字符串文字。

看来你的数组是在任何函数之外声明的。如果可以在函数中声明它，例如在main中。

Answer 2

在创建数组时，它的大小必须是常量，因为C不允许数组大小的非常量值。

C99标准部分6.7.8（初始化），第4点：

具有静态的对象的初始值设定项中的所有表达式存储持续时间应为常量表达式或字符串文字。

我确实更改了您的代码。试试吧。

#include <stdio.h>

#define Hall_1 10
#define Hall_2 20
#define Hall_3 30   

int main() 
{       
float  A,B,C;

A = Hall_1;
B = Hall_2; 
C = Hall_3;

float commutate_sequence[6][2]= {{B,A},{B,C},{A,C},{A,B},{C,B},{C,A}};
    return 0;
}

Answer 3

我改变了代码如下，现在可以使用了：

#define A Hall_1
#define B Hall_2
#define C Hall_3
void commutate(unsigned char max_min)
{ unsigned char X=0, i=0; 
float comt_sequence[6][2]= { (&Hall_2,&Hall_1) , (&Hall_2,&Hall_3),(Hall_1,&Hall_3) ,  (&Hall_1,&Hall_2),                                                             &Hall_3,&Hall_2) , (&Hall_3,&Hall_1) };
for (i=0; i<6 ;i++)
{ if( (max_min[0] == (*comt_sequence[i][0])) && (max_min[1] == (*comt_sequence[i][1]))) X=i;}

C数组初始化获取错误

3 个答案: