请问为什么另一个c文件中定义的全局变量在main.c中调用不了？

BayMax丶 · 发表于 2017-11-2 22:03:54

我最近在做小车，用定时器调制PWM脉冲控制速度，控制占空比的变量在motor.c中有定义，我主函数中想去改变这个变量的值来改变占空比控制电机的速度
下面这种写法是可以的

但是这种这一种写法就不行，在主程序里面只要给ZKB赋值ZKB就一直保持为0

请问为什么在main函数中调用其它c文件中定义的变量就会出错呢？[mw_shl_code=c,true]#include "Motor.h"

//extern ZKB;

void main(void)
{
MotorInit();

while(1)
{
PWM_change();
}
}

#ifndef __MOTOR_H_
#define __MOTOR_H_

#include <reg52.h>

#define uchar unsigned char

//#define GoForward { Left_Ctrl = 1; Right_Ctrl = 1; Left_IN1 = 1; Left_IN2 = 0; Right_IN1 = 1; Right_IN2 = 0;}
//#define Stop { Left_Ctrl = 0; Right_Ctrl = 0; }
//#define TurnLeft { Left_Ctrl = 1; Right_Ctrl = 1; Left_IN1 = 0; Left_IN2 = 1; Right_IN1 = 1; Right_IN2 = 0; }
//#define TurnRight { Left_Ctrl = 1; Right_Ctrl = 1; Left_IN1 = 1; Left_IN2 = 0; Right_IN1 = 0; Right_IN2 = 1; }

#define GoForward P2  = 0XAF
#define Stop P2 &= 0XF3
#define TurnLeft P2  = 0X9F
#define TurnRight P2  = 0X6F

sbit Left_IN1  = P2^7;
sbit Left_IN2  = P2^6;
sbit Left_Ctrl = P2^3;

sbit Right_IN1 = P2^5;
sbit Right_IN2 = P2^4;
sbit Right_Ctrl= P2^2;

void MotorInit(void);
void PWM_change(void);

#endif

#include "Motor.h"
#include "delay.h"
uchar counter;
uchar ZKB;
uchar ZKB_UpperLimit;

void PWM_change(void)
{
uchar i;
for(i=0;i<200;i++)
{
ZKB=i;
delayms(2);
}
for(i=200;i>0;i--)
{
ZKB=i;
delayms(2);
}
}

void MotorInit(void)
{
//PWM为500Hz，单周期2MS，设置20级调速，每次中断函数处理时间为100个单指令周期

EA = 1;
ET0 = 1;

TMOD = 0x02; //定时器0自动重载
TH0 = 0x9C;
TL0 = 0x9C;
TR0 = 1;

counter = 0;
ZKB_UpperLimit = 200;

ZKB = 0.5 * ZKB_UpperLimit;
}

void Motor_INT() interrupt 1
{
counter++;
if (counter <= ZKB)
{
GoForward;
}

if (counter > ZKB)
{
Stop;
}

if (counter >= ZKB_UpperLimit)
{
counter = 0;
}
}
[/mw_shl_code]

mack13013 · 发表于 2017-11-2 22:03:55

本帖最后由 mack13013 于 2017-11-3 00:20 编辑

A.c文件
[mw_shl_code=c,true]//A.c
#include A.h
int nTmp = 0;[/mw_shl_code]

A.h文件
[mw_shl_code=c,true]//A.h
extern int nTmp;[/mw_shl_code]

main.c文件
[mw_shl_code=applescript,true]//main.c
#include A.h
//这里可以用nTmp了[/mw_shl_code]