74HC595輸出接按鍵,怎么讀取鍵碼
原理圖上邊Q1-Q7接了四個按鍵 595輸出，還要一個輸入IO來配合，就可以讀了。
仿真沒有什么問題，實際運用要考慮按鍵消抖問題。
- #include <reg51.H>
- #define uint unsigned int
- #define uchar unsigned char
- sbit P_HC595_SER = P2^0;
- sbit P_HC595_SRCLK = P2^1;
- sbit P_HC595_RCLK = P2^2;
- sbit KEY=P2^3;
- unsigned char code table[]={0x70,0x79,0xee};//KEY.
- unsigned char code display[]={//0~f-.
- 0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,
- 0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71,0x40,0x80};
- unsigned char code wela[]={
- 0xfe,0xfd,0xfb,0xf7,0xef,0xdf,0xbf,0x7f};
- /**************** 向HC595發送一個字節函數 ******************/
- void Send_595(uchar dat)
- {
- uchar i;
- for(i=0;i<8;i++)
- {
- dat <<= 1;
- P_HC595_SER = CY; //溢出位賦值數據輸出端
- P_HC595_SRCLK = 1; //移位時鐘
- P_HC595_SRCLK = 0;
- }
- }
- /**************** 向HC595發送2個字節驅動碼 ******************/
- void DisplayScan()
- {
- static uchar i,j;
- Send_595(wela[i]);//向HC595發送位碼
- /**********根據位碼識別按鍵********/
- if(!KEY)
- {
- switch(i)
- {
- case 0: j= 4; break;
- case 1: j= 1; break;
- case 2: j= 2; break;
- case 3: j= 3; break;
- }
- }
- /******************************/
- if(i==3)
- Send_595(display[j]);//向HC595發送段碼顯示鍵值
- else
- Send_595(table[i]); //向HC595發送段碼顯示KEY.
- P_HC595_RCLK = 1; //鎖存輸出數據
- P_HC595_RCLK = 0;
- i++;
- i%=4;
- }
- void main()
- {
- P_HC595_SRCLK = 0;//初始化移位時鐘端
- P_HC595_RCLK = 0;//初始化鎖存輸出端
- while(1)
- {
- DisplayScan();
- }
- }
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