/**********************************************
*   File: DirKeyboard_3.C
*   Description: Direct Keyboard Interface Example
*   Created Date:  2007-10-01
*   Last Modified: 2007-10-01
*   Author: Jeffrey - Schicksal@126.com
*   Notes: None
**********************************************/
#include <REGX51.h>

unsigned char Read_Keyboard();

/**********************************************
*   Function: delay(unsigned int t)
*   Input Variables: t
*   Return Variables: None
*   Usage: Common Delay Routine, t as the delay time ticks
**********************************************/
void delay(unsigned int t)
{
		for(;t>0;t--);		// 延時(shí)循環(huán)
}

/**********************************************
*   Function: main()
*   Input Variables: None
*   Return Variables: None
*   Usage: Program Entry
*********************************************/
void main()
{
		unsigned char LED_Status = 0xff;			// 定義鍵值
		unsigned char Keyboard_Status = 0xff;		// 定義鍵值
		unsigned char Keyboard_Status_Old = 0xff;	// 上一次的鍵值保持
		unsigned char jTemp;						// 臨時(shí)變量
		unsigned char iTemp;						// 臨時(shí)變量
		while(1)
		{
				Keyboard_Status = Read_Keyboard();			// 讀取按鍵值
				if(Keyboard_Status != Keyboard_Status_Old)	// 如果有鍵狀態(tài)發(fā)生改變
				{
					jTemp = Keyboard_Status^Keyboard_Status_Old; // 計(jì)算狀態(tài)改變的位
					for(iTemp = 1;iTemp<129;iTemp<<1) 			 // 掃描狀態(tài)位	
					{
						if(iTemp&jTemp)  						 // 狀態(tài)改變
						{
							if(iTemp & Keyboard_Status_Old)		 // 按鍵被按下
							{
								LED_Status ^= iTemp; 	  		 // Toggle LED
							}
							else								 // 按鍵釋放
							{
								// Nothing							  // 不做任何操作
							}
						}
					}
				}
				P0 = ~LED_Status;								 // 點(diǎn)亮相應(yīng)的LED燈
				
				//********************主程序部分*********************//
				// Add your code here
				//********************主程序部分*********************//
		}
}
	
/**********************************************
*   Function: Read_Keyboard
*   Input Variables: None
*   Return Variables: Keys Value
*   Usage: Read Keyboard Status
*********************************************/
unsigned char Read_Keyboard()
{
		unsigned char Keys_Value;					 // 定義鍵值變量
		unsigned char Keys_Temp;
		
		do
		{
			P2 = 0xff;									 // P2口置高，準(zhǔn)備讀取按鍵狀態(tài)
			Keys_Temp = P2;							 	 // 讀取按鍵狀態(tài)
			delay(150);									 // 消抖延時(shí)
			P2 = 0xff;									 // P2口置高，準(zhǔn)備讀取按鍵狀態(tài)
			Keys_Value = P2;							 // 讀取按鍵狀態(tài)
		}
		while(Keys_Value != Keys_Temp);			 // 如果讀取狀態(tài)不一致，則重復(fù)讀取鍵值
		return Keys_Value;							 // 返回按鍵狀態(tài)值
}