MCU function signal generator, output four kinds of waveforms, adjustable frequency, schematic diagram, simulation and C program

The design requirements

1. With MCS-51 Series single chip microcomputer is the control device , use C Language for program development , Combined with peripheral electronic circuits , Design a function signal generator system ;

2. Can produce a sine wave 、 square wave 、 Triangular wave and sawtooth wave 4 Kinds of waveform ;

3. Extended keyboard input circuit , Used to switch the waveform type 、 Set the frequency size and step value ;

4. LCD1602 The display circuit displays the current waveform type in real time 、 Frequency value and other information ;

5. Adjustment range of waveform frequency value ：10~100Hz;

6. Frequency step value adjustment range ：0.1~10Hz;

System Overview
This article is based on 51 Function signal generator system designed by single chip microcomputer , Can produce a sine wave 、 square wave 、 Triangular wave and sawtooth wave 4 Kinds of waveform , And the waveform frequency is adjustable , The adjustment range is 10~100Hz.

System consists of 5V Power supply module 、AT89C51 Minimum system of single chip microcomputer 、DAC0832 A / D conversion circuit 、LM358 Amplification circuit 、LCD1602 LCD circuit 、 Key circuit and LED The indicator circuit consists of .

The system framework is as follows ：

Working principle is ： Digital signal generated by single chip microcomputer , the DAC0832 Convert to analog signal , Re pass LM358 After the operation circuit is amplified , Output 4 A waveform with adjustable frequency .

The type and frequency value of the waveform are determined by LCD Liquid crystal display (LCD) , The switching of waveform and the adjustment of frequency are controlled by keys . meanwhile ,4 A different color LED As indicator lights of different waveforms .

Simulation circuit diagram


Schematic diagram

Analysis of simulation results
Open the function signal generator simulation file , Double click the MCU to load Signal.hex file （ be located C In the program folder ）, Run the simulation , give the result as follows .

LCD1602 The first line of LCD shows Wave：Sine, The second line shows Freq：10.0Hz. Indicates that the current initialization waveform is 10Hz The sine wave of , At the same time, the green corresponding to the sine wave LED The light is on .

Besides , The system will pop up the oscilloscope window automatically , Display the waveform . In this system , The signal output terminal is connected to the... Of the oscilloscope A passageway .

Simulation runtime , If the oscilloscope window is accidentally closed or does not pop up , Right click the oscilloscope , Click... In the drop-down menu Digtal Oscilloscope Can be restored .

In the system , Four keys are used to control the switching of waveform types 、 Increase or decrease of frequency value and increase or decrease of frequency step value .

Click on “ Switch ” key , Sine wave can be realized 、 square wave 、 Triangular wave and sawtooth wave 4 Switching back and forth between waveforms ;

In waveform frequency display mode ,“ increase ” and “ Reduce ” Key is used to increase or decrease the frequency of the current waveform , The default frequency step value of the system is 0.1, Press once “ increase ” or “ Reduce ” key , The change of frequency is 0.1Hz.

for example , We switch the waveform to square wave , Set its frequency to 14.5Hz, give the result as follows . here , Red corresponding to square wave LED The light is on .

When pressed “ Stepping ” Post key , The system enters the step adjustment mode , As shown in the figure below .LCD Show Step value：0.1, Indicates that the current step value is 0.1Hz. here ,“ increase ” and “ Reduce ” key , Used to change the size of the step value .

for example , We set the frequency step value to 3Hz, The results are shown below . After setting , Press again “ Stepping ” key , The system exits the step adjustment mode , Return to frequency display mode . At this time , Press down “ increase ” or “ Reduce ” key , The change amplitude of the frequency value is 3Hz.
below , We set the system output frequency to 50Hz Triangular wave sum 80Hz The square wave , give the result as follows .

in summary , The operation effect of the function signal generator simulation circuit meets the design requirements , Verify success .

part C Code

void keyscan()					// Key scan function 
{
    
	if(s1==0)					// Whether the frequency plus key is pressed 
	{
    	 
		EA=0;					// Turn off interrupt 
		delay(2);				// Delay chattering 
		if(s1==0)				// Judge again 
		{
    
			while(!s1);			// Release the button 
			pinlv+=bujin;		// The frequency increases in steps 
			if(pinlv>1000)		// The frequency value is maximum 100Hz
			{
    
				pinlv=100;
			}
			display();
/* The minimum frequency value is 10Hz,pinlv The value of is 100（ Because you want to display one decimal place ）,150000/100=1500, This 1500 That's what the timer needs to count , The unit is us,65536-1500 What you get is the initial value of the timer ,  Regardless of the initial value , Look at the timing first ,1500us, The period of a waveform is determined by 64 Composed of two timing , therefore , A waveform period is 64*1500us=96000, That is to say 96ms, Appointment etc   On 100ms, That is to say 10Hz The frequency of */
			m=65536-(150000/pinlv);	  // Calculate the frequency 
			a=m/256;				  // Assign the initial value of the timer to the variable 
			b=m%256;
			EA=1;					  // Turn on the interrupt master switch 
		}
	}
	if(s2==0)					  // Whether the frequency reduction key is pressed 
	{
    	 
		
		delay(5);
		if(s2==0)
		{
    
			EA=0;	
			while(!s2);
			pinlv-=bujin;
			if(pinlv<100)
			{
    
				pinlv=1000;
			}
			display();
			m=65536-(150000/pinlv);
			a=m/256;
			b=m%256;	
			EA=1;
		}
	}
	if(s3==0)					   // Whether the waveform switching key is pressed 
	{
    	 
		delay(5);
		if(s3==0)
		{
    
			EA=0;
			while(!s3);
			boxing++;
			if(boxing>=4)
			{
    
				boxing=0;
			}
			display();
			EA=1;
		}
	}	
}

Resource content
（1） be based on 51 MCU function signal generator design paper complete version ;
（2）Keil C Program ;
（3）Proteus Simulation ;
（4） Schematic file ;
（5）Visio Flow chart file ;
（6） List of components ;
（7） Reference material ;

Resource screenshot




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