42 lines
855 B
C
42 lines
855 B
C
#include "hc165.h"
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//初始化74hc165
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void _74hc165_init(void)
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{
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HC165_LD(1); //LD拉高，不读取按键状态
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HC165_CLK(1); //时钟拉高，便于产生上升沿
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}
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//读取74HC165
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uint16_t _74hc165_read_byte(void)
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{
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unsigned char i;
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unsigned int temp = 0;
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HC165_LD(0); //LD拉低，读取按键状态
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delay_us(1);
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HC165_LD(1); //LD拉高，停止按键读取
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delay_us(1);
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if(HC165_DAT == 1) //等于1即并行输入D7引脚的按键被按下
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{
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temp |= 0x01; //最低位置1表示按键被按下，反之则没按键被按下
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}
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for(i = 0; i < 15; i ++) //因为最高位不用移位即可读取，故循环(8-1)次，依次把次高位移到最高位，第一级74HC165优先读取
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{
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temp = temp << 1;
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HC165_CLK(0); //HC165_CLK = 0 ——> HC165_CLK = 1 产生上升沿，次高位D(n-1)移到高位D(n)
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delay_us(1);
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HC165_CLK(1);
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// delay_us(1);
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if(HC165_DAT == 1)
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{
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temp |= 0x01;
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}
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// delay_us(1);
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}
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return temp;
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}
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