46 lines
711 B
C
46 lines
711 B
C
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#include "ul.h"
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#include "intrins.h"
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sbit Tx = P1 ^ 0;
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sbit Rx = P1 ^ 1;
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void Delay12us(void) //@12.000MHz
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{
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unsigned char data i;
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_nop_();
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_nop_();
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i = 33; // 38
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while (--i);
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}
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void Ut_Wave_Init() {
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unsigned char i;
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for (i = 0; i < 8; i++) {
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Tx = 1;
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Delay12us();
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Tx = 0;
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Delay12us();
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}
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}
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unsigned char Ut_Wave_Data() {
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unsigned int time;
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CH = CL = 0;
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CMOD = 0x00;
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EA = 0;
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Ut_Wave_Init();
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EA = 1;
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CR = 1;
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while (Rx && !CF);
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CR = 0;
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if (!CF) { // us -> s 10^(-6)
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// m -> cm 10^2
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// 10^(-4)
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// L = V*T/2=340*time/2=170*10^(-4)*time=0.017*time
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time = CH << 8 | CL;
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return (0.017 * time + 3);
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} else {
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CF = 0;
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return 0;
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}
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}
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