The microcontroller generates a 38KHZ square wave at the IO port

/************************************************

  This function will continuously generate a 38KHZ square wave at the P3^0 port of the microcontroller.

**********************************************/

#include //Includes special function register library

sbit P3_0=P3^0;

void main()

{

TMOD = 0x02; //TMOD is the timer mode control register, here timer 0 is selected, working in mode 2

TL0 = 0xF3; //Timer initial value

TH0 = 0xF3; //Timer initial value

EA = 1; // Enable general interrupt

ET0 = 1; // Enable CPU interrupt and T0 interrupt

TR0 = 1; //Start the timer

while(1);

}

void time0_int(void) interrupt 1 //Timer 0 interrupt service routine. Except for the function name, the other parts should be written in this format.

{

P3_0 = ~P3_0;

}

/*

******Calculation of initial value of timer************

If timer 0 is used, working in mode 1:

(2^8 - X)*oscillation period*12 = timing time

The crystal oscillator I use here is 12MHZ, that is, the oscillation period is 1/12MHZ = 1 microsecond.

To generate a 38KHZ square wave, that is, 1/38KHZ = 26 microseconds, the timer should be set to 13 microseconds to ensure that a square wave with a period of 26 microseconds can be generated at P3^0. The initial count value X = 253 (0xF3)

*/

/*

***************Timer Mode Selection*******************

The timer has four working modes. In principle, it can work in any mode, but working in mode 2 is more accurate and has a smaller error. This is because the timer in mode 2 has the feature of automatically reloading the initial value.

*/

/*

********Writing of interrupt service routine***********

void function name() interrupt interrupt number

{

}

Interrupt number

 0 External interrupt 0

 1 Timer 0

 2 External interrupt 1

 3 Timer 1

 4 Serial interrupt

Here we use timer 0, so the interrupt function is written as

void void time0_int(void) interrupt 1

{}

*/

/*

********Start and stop the timer**********

As long as TR0 = 1, timer 0 is started, and TR0 = 0, timer 0 is stopped.

*/