l298n驱动步进电机实验

步进电机型号是28byj-48

之前有用过uln2003驱动，也是出现一样的问题，而且电机发热很快

程序是
#include<reg51.h>
#define uchar unsigned char
sbit jia_key = P3^6;
sbit jian_key = P3^7;
uchar num = 5;
uchar code table[] = {
0xfe, 0xfc, 0xfd, 0xf9, 0xfb, 0xf3, 0xf7, 0xf6};
void delay(uchar i)
{
uchar j, k;
for(j = i; j > 0; j--) for(k = 125; k > 0; k--);
}
void key()
{
if(jia_key == 0) {
delay(5);
if(jia_key == 0) {
num++;
if(num == 9) num = 8;
while(jia_key == 0);
}
}
if(jian_key == 0) {
delay(5);
if(jian_key == 0) {
num--;
if(num == 0) num = 1;
while(jian_key == 0);
}
}
// 1 <= num <= 8
P2 = num; //外接LED可以当场看到num的值.
}
void qudong()
{
uchar j, i;
for(j = 0; j < 8; j++) {
P1 = table[j];
for(i = 0; i < num; i++) delay(20);
}
}
void main()
{
while(1) {
key();
qudong();
}
}

跪求大神来解释这是为什么？需要怎么解决啊