MCU simulates switch light

1. Verification Task

As shown in Figure 4.2.1, the monitoring switch K1 (connected to the P3.0 port) is used, and the light-emitting diode L1 (connected to the P1.0 port of the microcontroller) is used to display the switch status. If the switch is closed, the L1 light is on, and if the switch is open, the L1 light is off.

2-way schematic

Figure 4.2.1

3 Hardware connections on the system board

(1) Connect the P1.0 port in the "MCU System" area to the L1 port in the "Eight-way LED Indicator Module" area with a wire;

(2) Connect the P3.0 port in the "MCU System" area to the K1 port in the "Four-way Slide Switch" area with a wire;

4. Programming content

(1) Off state detection process

The detection of switch status by the MCU is to input the signal from the P3.0 port of the MCU, and the input signal has only two types: high level and low level. When the switch K1 is turned up, the high level is input, which is equivalent to the switch being disconnected. When the switch K1 is turned down, the low level is input, which is equivalent to the switch being closed. The MCU can use the JB BIT, REL or JNB BIT, REL instructions to complete the detection of the switch status.

(2) Output control

As shown in Figure 3, when the P1.0 port outputs a high level, that is, P1.0=1, according to the unidirectional conductivity of the light-emitting diode, the light-emitting diode L1 is off; when the P1.0 port outputs a low level, that is, P1.0=0, the light-emitting diode L1 is on; we can use the SETB P1.0 instruction to make the P1.0 port output a high level, and use the CLR P1.0 instruction to make the P1.0 port output a low level.

5 Sequence diagram

Figure 4.2.2[page]

6. Compile source code

                            ORG 00H

START:               JB P3.0,LIG

                            CLR P1.0

                           SJMP START

LIG: SETB P1.0

                            SJMP START

                           END

7. C language source program

#include

sbit K1=P3^0;

sbit L1=P1^0;

void main(void)

{

  while(1)

    {

      if(K1==0)

        {

          L1=0; //light on

        }

        else

          {

            L1=1; //light off

          }

    }

}

The above is the complete source code of the microcontroller analog switch light