Controlling a Motor with 8051 Microcontroller and L298N Motor Driver

Today we are going to use the L298N motor driver with 8051 microcontrollers to control a DC Motor. This motor control system is specially for robotic 2-wheel differential drive car. Or could be used with any other use case where we need to drive one or two motors with the push buttons.

The program which we are demonstrating in this post is 4 push button interfaced with 8051 microcontroller. We read the button states continuously in our main loop and wait for any button to be pressed. Once any button is pressed, we jump to the respective action. We take 4 actions based on the push button. One action is for driving motor in forward direction. Which is achieved by moving both motors in similar forward direction. Second is reverse direction which is achieved by moving both motors in reverse direction. For turning right and left we move one respective motor in forward direction.

Understanding the L298N Motor Driver

he L298N is a popular H-bridge motor driver IC capable of driving two DC motors. It provides a simple and efficient way to control motor direction and speed. We will not touch the speed control part in this post as we will only be focusing on directional control with the help of L298N motor driver.

L298N Pin	Function
IN1	Input for Motor A, direction control
IN2	Input for Motor A, direction control
IN3	Input for Motor B, direction control
IN4	Input for Motor B, direction control
ENA	Enable input for Motor A
ENB	Enable input for Motor B
OUT1	Output to Motor A, high-side
OUT2	Output to Motor A, low-side
OUT3	Output to Motor B, high-side
OUT4	Output to Motor B, low-side
VSS	Ground
VDD	Power supply

Hardware Setup

The system comprises several essential components. The 8051 microcontroller acts as the system’s brain, processing instructions and controlling the overall operation. An L298N motor driver is employed to regulate the motor’s behavior based on signals received from the microcontroller. The DC motor, the system’s actuator, converts electrical energy into mechanical motion. A power supply provides the necessary electrical energy for both the microcontroller and the motor driver.

Software Implementation

Here we will discuss the Assembly language code for controlling the motor direction with the help of 8051 microcontroller. First of all, we have to define the pins which we are using for our switches and L298N motor driver direction control. Remember we pulled the ENA and ENB pins to 5 volt giving full speed to the motors.

OUT1  BIT  P2.0
OUT2  BIT  P2.1
OUT3  BIT  P2.2
OUT4  BIT  P2.3
SW1  BIT  P0.0
SW2  BIT  P0.1
SW3  BIT  P0.2
SW4  BIT  P0.3Code language: AVR Assembler (avrasm)

These lines define the bit addresses for motor control outputs and switch inputs.

Now coming to our main loop it looks like this.

ORG  00H


MAIN:  
  SETB  OUT1
  SETB  OUT2
  SETB  OUT3
  SETB  OUT4



AGAIN:

 JNB  SW1,ACTION1
 JNB  SW2,ACTION2
 JNB  SW3,ACTION3
 JNB  SW4,ACTION4
 ACALL         DELAY1 
 SJMP  AGAIN

The main section initializes all motor outputs to high, effectively stopping the motor. The Again loop continuously checks the state of the switches and jumps to the corresponding action if a switch is pressed.

The delay function is pretty much similar to all our previous posts.

DELAY1:
 MOV  R7,#255
 DJNZ  R7,$
 RET


DELAY3:
 MOV  R7,#3
D3L2: MOV  R6,#255
D3L1: MOV  R5,#255   
 DJNZ  R5,$
 DJNZ  R6,D3L1
 DJNZ  R7,D3L2
 RET

ENDCode language: PHP (php)

our subroutines for driving motors forward, reverse, right, left and stopping the motors looks like following. .

FWD:
 CLR  OUT1
 SETB  OUT2
 ACALL DELAY1
 RET

REV:
 SETB  OUT1
 CLR  OUT2
 ACALL DELAY1
 RET

RIGHT:
 CLR  OUT3
 SETB  OUT4
 ACALL DELAY1
 RET

LEFT:
 SETB  OUT3
 CLR  OUT4
 ACALL DELAY1
 RET

STOP1:
 SETB  OUT1
 SETB  OUT2
 ACALL DELAY1
 RET

STOP2:
 SETB  OUT3
 SETB  OUT4
 ACALL DELAY1
 RET
Code language: ARM Assembly (armasm)

Finally our 4 actions are as follows.

ACTION1:
 ACALL FWD
 ACALL DELAY3
 ACALL STOP1
 SJMP  AGAIN

ACTION2:
 ACALL REV 
 ACALL DELAY3
 ACALL STOP1
 SJMP  AGAIN

ACTION3:
 ACALL RIGHT
 ACALL DELAY3
 ACALL STOP2
 SJMP  AGAIN

ACTION4:
 ACALL LEFT
 ACALL DELAY3
 ACALL STOP2
 SJMP  AGAINCode language: HTTP (http)

Additional Considerations

Ensure the motor power supply is sufficient to meet the motor’s demands. Given its capability to generate heat, especially when driving high-current motors, consider using a heat sink for the L298N motor driver. Optimizing the code for efficiency and performance is crucial. Implementing error handling mechanisms can detect issues like motor stalls or overcurrent, enhancing system robustness. Finally, incorporating sensors such as encoders or current sensors can provide valuable feedback for advanced motor control applications.