51 MCU Self-study Notes (IV) - Lighting up LED lights and running lights

LED Light

LED stands for semiconductor light emitting diode, which is made of semiconductor materials. It is a light-emitting device that directly converts electrical energy into light energy and electrical signals into light signals. It has the characteristics of low power consumption, high brightness, bright colors, vibration resistance, long life (normal light emission time is 80,000-100,000 hours), cold light source, etc. It is a real "green lighting". Actual picture:

The symbol of LED in the circuit diagram is:

It has the basic characteristics of a diode, that is, it conducts in the forward direction and is cut off in the reverse direction. To light up the LED, an operating current needs to flow in the forward direction.

The operating voltage drop of different LED lights is different. The operating voltage drop range of ordinary light-emitting diodes is: 1.6-2.1V. The operating current is: 1-20mA.

Light up the LED in the microcontroller

Schematic diagram of LED module in single chip microcomputer:

By observing the circuit schematic, it can be concluded that to light up the small LED light on the development board, you only need to control the P2 port to output a low level (that is, assign a value of "0" to the P2 port).

1. Light up all LED lights on the microcontroller

code show as below:

#include

sbit LED1 = P2^0;

sbit LED2 = P2^1;

sbit LED3 = P2^2;

sbit LED4 = P2^3;

sbit LED5 = P2^4;

sbit LED6 = P2^5;

sbit LED7 = P2^6;

sbit LED8 = P2^7;

void main()

{

  LED1 = 0;

  LED2 = 0;

  LED3 = 0;

  LED4 = 0;

  LED5 = 0;

  LED6 = 0;

  LED7 = 0;

  LED8 = 0;

}

The results are as follows:

2. The LED light flashes

Code:

#include

unsigned int i;

void main()

{

  while(1)

  {

    P2 = 0;

    i = 65535;

    while(i--);

    P2 = 0xff;

    i = 65535;

    while(i--);

  }

}

3. Flowing lights

Code:

#include

#include

#define uint unsigned int

#define uchar unsigned char

uchar temp;

void delay(uint z)

{

  uint x,y;

  for(x = z;x > 0;x--)

     for(y = 114;y > 0;y--)

}

void main()

{

   temp = 0xfe;

   P2 = temp;

   delay(100);

   while(1)

   {

      temp = _crol_(temp, 1);

      P2 = temp;

      delay(100);

   }

}