74HC595扩展按键扫描---调试笔记

问题出现在了按键扫描过程中，使用延时，但是为什么使用延时就检测不到，还是没琢磨明白。

#include "hc595.h"

/*------------------------------------------------ 按键扫描程序 ------------------------------------------------*/

unsigned char keyscan(void) { unsigned char Val; SendByte(0x1b); LINE_SET;

if((P4&0x70)!=0x70) {

Val = P4&0x70; Val+=0x1b; while((P4&0x70)!=0x70); delay_10ms(1); while((P4&0x70)!=0x70); return Val;

} SendByte(0x17); LINE_SET;

if((P4&0x70)!=0x70) {

Val = P4&0x70; Val+=0x17; while((P4&0x70)!=0x70); delay_10ms(1); while((P4&0x70)!=0x70); return Val;

}

SendByte(0x0f); LINE_SET;

if((P4&0x70)!=0x70) {

Val = P4&0x70; Val+=0x0f; while((P4&0x70)!=0x70); delay_10ms(1); while((P4&0x70)!=0x70); return Val;

} SendByte(0x1d); LINE_SET;

if((P4&0x70)!=0x70) {

Val = P4&0x70; Val+=0x1d; while((P4&0x70)!=0x70); delay_10ms(1); while((P4&0x70)!=0x70); return Val;

} SendByte(0x1e); LINE_SET;

if((P4&0x70)!=0x70) {

Val = P4&0x70; Val+=0x1e; while((P4&0x70)!=0x70); delay_10ms(1); while((P4&0x70)!=0x70); return Val;

}

return 0xff; }