51 single chip microcomputer measures the period of square wave signal

utilize T0 As timer ,T1 As a counter ;

Main idea ：

1、T1 Count , Working mode ： The way 2;T0 timing , Working mode ： The way 1

2、T1 Octet count , Assign initial value to 0xFF, Turn on interrupt , Start counting （P3.5 Input the measured square wave signal ）

3、 Get into T1 interrupt ： if TR0=0, Start timing TR0=1,TH/L1=0xF6（ Measure ten cycles ）; if TR0=1, Then stop timing TR0=0 And stop counting TR1=0; Record the current T0 Timing results , Get the period of the square wave .

Be careful ：

1. TH/L1=0xF6 For measuring ten cycles , The purpose is to increase the measured value , Reduce the proportion of measurement error . If it is deleted, the time of one cycle will be measured .
2. T0 Work in the way 1 There are sixteen , At most one time 71ms（ Crystal oscillator ：11.0592MHz）
3. T0 The result should be converted into time according to the crystal vibration frequency of the single chip microcomputer , If the crystal oscillator is 11.0592M, You need to ×12/11.0592（us）

C51 Timer settings

// Timer settings 
void Init_T(){
	TMOD=0x61;  //T1 Counting works in 2 Pattern ;T0 Timing work in 1 Pattern 
	TL0=0x00;
	TH0=0x00; //T0 Initial value 0, It can be timed 71ms
	TL1=0xFF;
	TH1=0xFF; //T1 Initial value 255, Count 1 Trigger interrupt ;
	EA=1;
	ET1=1;// Turn on T1 interrupt 
	ET0=1;// Turn on T0 interrupt 
	TR1=1;
	TR0=0;
}

// Timer interrupt setting 
void timer1() interrupt 3 using  2{
	if(!TR0){
	TH0=0x00;
	TL0=0x00;
	TH1=0xF6;
	TL1=0xF6;
	TR0=1;
	}
	else{
	TR0=0;
	TR1=0;
	time=0;
	time=TH0;
	time=time<<8;
	time=time|TL0;
	}	
}

If you feel this article is useful, just give it a compliment and encouragement @[email protected]

If there are other methods to accurately measure the period or think this article is wrong , Welcome to the comment area or private letter discussion and exchange ~