51 MCU as a signal generator example programming-EEWORLD

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//Use the 51 single-chip microcomputer as a signal generator to output square waves of four frequencies at the same time.

//Requirement: The crystal oscillator is 12MHz, T0 is used as the timer, and the lower four bits of P1 output four frequencies of square waves:

// P1.3 = 1.25kHz, P1.2 = 2.5kHz, P1.1 = 5kHz, P1.0 = 10kHz

//In addition, the above four frequencies require a four-to-one data selector to select one of them for output. //
The outputs of P1.6 and P1.7 are used to control the selection bits of the four-to-one data selector, which are controlled by the P3.0 button.
//====================================================
//Now I have added PROTEUS simulation pictures to the blog.
//The title requires that the four frequencies output on the four adjacent interface lines have a double relationship, which can be completed using a timer interrupt.
//The title also requires the use of a data selector to select a frequency to output by pressing a button.
//The screenshots of PROTEUS simulation are shown below.
//In the figure, a frequency meter and a speaker are connected to the output end for frequency detection.
//When the button is pressed, the output frequency can be switched in turn.
//The screenshots of the detection results of the four frequencies are all shown in the figure. It can be seen that the output frequency is very ideal.
//The PC speaker can also hear the sound, the frequency of 10kHz, which is quite harsh.

//The following program has been simulated successfully.
//---------------------------------------------------
#include
#define uchar unsigned char
#define TL_0SET (256 - 50) //The timing time is selected as 50us
//The output square wave period will be 100us, 10kHz
sbit P3_2 = P3^2; //For buttons
sbit P1_0 = P1^0; //Four frequency outputs
sbit P1_1 = P1^1; //
sbit P1_2 = P1^2; //
sbit P1_3 = P1^3; //
sbit P1_6 = P1^6; //Two selection control outputs
sbit P1_7 = P1^7; //

bdata uchar x = 0;
sbit p16 = x^0;
sbit p17 = x^1;

uchar i, j;
//---------------------------------------------------
void e0int() interrupt 0 //External interrupt 0 acts as a switch to control the four-choice data selector
{
while(P3_2 == 0) {;} //Wait for the button to be released
x++;
if(x == 4) x = 0; //Change the current output selection
P1_7 = p16;
P1_6 = p17;
}
//---------------------------------------------------
void time0() interrupt 1 //T0's interrupt service routine
{ //T0 works in mode 2 and automatically loads the initial value
i++;
j = i % 16; //Get the lower four bits of i
j += x << 6; //Combined data selector control signal
P1 = j; //Output four frequencies of square wave and control signal
}
//---------------------------------------------------
void main()
{
TMOD = 0x02; //T0 timing mode 2
TH0 = TL_0SET; //Self-loaded timing initial value
TR0 = 1; //Start T0
ET0 = 1;
IT0 = 1; //External interrupt 0 is triggered by falling edge
EX0 = 1; //External interrupt 0 enables
EA = 1;
while(1) {;}
}
//---------------------------------------------------

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