Working with STM32 and Motors part 1 : Stepper Motor

In this guide,, we will learn to interface a stepper motor with STM32F411RE Nucleo-64. There are many options available for stepper motors. But in this tutorial, we will use an inexpensive 28BYJ-48 stepper motor for interfacing with STM32F411. Because it comes with a UL2003 driver. Moreover, it is a low-cost solution to learn about stepper motors control and working. But the concepts learned with this type can be easily applied to other high torque industrial stepper motors also.

In this guide, we will cover the following:

• 28BYJ-48 Stepper Motor
• Connection diagram
• Code
• Demo

1.1 28BYJ-48 Stepper Motor pin configuration:

The following figure shows the pinout diagram of 28BYJ-48 stepper motor. It consists of 5 pins. Out of these 5 pins, four pins are used to provide sequence logic to the coils and one pin is +5 volts supply pin. 

1.2 Pin Configuration Details

The specifications of the S8BYJ-48 stepper motor are:

• It is a unipolar 5 pin coil with a rated DC voltage of 5V.
• It has 4 phases with a stride angle of 5.625°/64.
• The frequency of this stepper motor is 100Hz and insulated power is 600VAC/1mA/1s.
• The half-step method is recommended for driving this stepper motor.
• The value of pull in torque for a stepper motor is 300 gf.cm.

1.3 ULN2003 Stepper Motor Driver Module

Now the first question which comes to your mind is why do we need a ULN2003 driver to drive stepper motors? This is because the current consumption of 28BYJ-48 is around 240mA. That means the current required to drive coils by applying a sequence of control signals is also almost 200mA. GPIO pins of STM32F411 can not provide current of this magnitude. Therefore, we need a ULN2003 driver which translates low current output of TM4C123 GPIO pins into higher current that meets the requirement of stepper motor control signals. 

Stepper Motor Driver Module Pinout

ULN2003 driver IC consists of 7 darlington pair transistor outputs. Each output can drive 500mA and 50V load. The input to each 7 darlington pair transistor can be a signal from the microcontroller such as STM32F411 microcontroller. To drive a stepper motor, this driver board used only four outputs. The following diagram shows the ULN2003 motor driver board and details of their components: 

2.1 Connection:

So far, we learnt about the stepper motor and it’s driver. Let’s continue with the actual connection to STM32F411 and how to code

PC0->IN1

PC1->IN2

PC2->IN3

PC4->IN4

2.2 Driving Modes

Full Drive Sequence Mode

In this mode, two coils are energized at a time that means two windings of stepper motor energized together. Therefore, motor runs at full torque. We apply this sequence to input pins of the stepper motor through a UNL2003 driver. 

Half Drive Sequence Mode

In this mode, we control the phases or coils with alternate one and two phase control as shown in the table below. But, in this mode, motor runs at low torque. 

Wave Drive Mode 

Like full-drive mode, only one coil is turned on at a time but with a drive sequence as shown below. The only advantage of this method is that a stepper motor consumes less power. 

We shall use Full drive sequence mode

3. Code:

#include "stm32f4xx.h"                  // Device header
//delay in millisecond
void Delay_ms(int delay)

{

int i;

for(; delay>0 ;delay--)

{

for(i =0; i<3195;i++);

}

}



int main(void)
	{
	//Enable clock access to GPIOC
	RCC->AHB1ENR|=RCC_AHB1ENR_GPIOCEN;
	//Set PC0, PC1, PC2 and PC3 to output
	GPIOC->MODER|=GPIO_MODER_MODE0_0|GPIO_MODER_MODE1_0|GPIO_MODER_MODE2_0|GPIO_MODER_MODE3_0;
	
	while(1)
		{
		for(int i=0; i<500; i++) // take 500 steps to complete one revolution 
		{
		//apply full drive clockwise rotation sequence 
	  GPIOC->ODR = 0x08;
    Delay_ms(4);
    GPIOC->ODR = 0x04;
    Delay_ms(4);
    GPIOC->ODR = 0x02;
    Delay_ms(4);
    GPIOC->ODR = 0x01;
    Delay_ms(4);
}
Delay_ms(1000);
for(int i=0; i<100; i++) // rotate 100 steps counter clockwise 
		{
		
	  GPIOC->ODR = 0x01;
    Delay_ms(4);
    GPIOC->ODR = 0x02;
    Delay_ms(4);
    GPIOC->ODR = 0x04;
    Delay_ms(4);
    GPIOC->ODR = 0x08;
    Delay_ms(4);
}

		Delay_ms(1000);
		}
	
	}

4. Demo

Note: My stepper motor sometimes gets stuck for some reason.

Happy Coding 😀