What could be the reasons for a stepper motor stuttering with an A4988 driver?
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I am using an A4988 Stepper Motor Driver, which is controlled with an STM32F767ZI on a Nucleo 144 board. The stepper motor takes 12 V with a maximum of 350 mA.
When powered, the motor simply flickers and stutters, but moves at a negligible speed.
Here is a circuit diagram of the setup, with voltage readings taking from a multimeter:
The potentiometer has been set correctly.
The same results occur even with two other A4988 drivers.
For reference, here is the code (though I don’t believe this is a software issue):
main.c
#include "./headers/stm32f767xx.h"
#include <stdint.h>
int main(void)
{
initMotor(0); // initialise the motor
initLed(7); // initialise the led
unsigned long a = 0;
while (1)
{
if (a == 50000)
{
toggleLed(7); // this LED flashes a little quicker than twice per second
stepMotor(0); // output a pulse to the driver to step the motor, attached to PA2
a = 0;
}
a++;
}
}
./drivers/led.c
#include "../headers/stm32f767xx.h"
void initLed(int pin)
{
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN; // enable the GPIOB clock
GPIOB->MODER |= (0x1 << (pin * 2)); // set to output
GPIOB->OTYPER = 0x00; // push-pull mode
GPIOB->ODR = 0x00; // set output register to 0 across all pins
}
void toggleLed(int pin)
{
GPIOB->ODR ^= (0x1 << pin); // toggle the pin
}
./drivers/motor.c
#include "../headers/stm32f767xx.h"
void initMotor(int step_pin)
{
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN; // enable the GPIOA clock
GPIOA->MODER |= (0x1 << (step_pin * 2)); // set to output
GPIOA->OTYPER = 0x00; // push-pull mode
GPIOA->PUPDR |= (0x2 << (step_pin * 2)); // pull down the pin specified
GPIOA->ODR = 0x00; // set output register to 0 across all pins
}
void stepMotor(int step_pin)
{
GPIOA->ODR |= (1 << step_pin); // output to the pin specified
GPIOA->ODR &= ~(1 << step_pin); // reset the output back to 0
}
With this code, I was expecting the motor to take steady and even steps, rather than the backwards-and-forwards stuttering it does.
I would appreciate any suggestions for the direction I should take from here, or any suggestions as to what the issue could be.stm32stepper-motorstepper-driverShareCiteEditFollowFlagasked yesterdayuser152789782111 bronze badge New contributor
- 1Do you have a datasheet for the stepper? The first thing to check would be that the phases of the stepper motor are correctly connected to the A4988 outputs. – gcr yesterday
- 1Are you sure ‘stepMotor’ function works to send a ~50% duty cycle PWM? – Ernesto yesterday
- 1@tlfong01 i have slowed it down, and the result is still the same – user15278978 19 hours ago
- 1@gcr i believe the only wiring concern with the motor is that one coil of the motor is connected to a number pair (1A with 1B, 2A with 2B), as outlined in this image (which is what I have done) – user15278978 19 hours ago
- 1@Ernesto nope, it doesn’t. i was under the impression that any change to a high signal sent to the step pin of the A4988 would step the motor. i’ll give this a go – user15278978 19 hours ago
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1 Answer
Question
MCU STM32 with stepper motor driver Allegro A4988 are moving a 2 coil, 4 wire, bipolar stepper motor ridiculously slowly, with flickers and stutters. How to fix?
The OP’s original code (See Appendix A, B, and C below)
Answer
The schematic v0.1
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References
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Appendices
Appendix A – The OP’s Original Code – main.c
#include "./headers/stm32f767xx.h"
#include <stdint.h>
int main(void)
{
initMotor(0); // initialise the motor
initLed(7); // initialise the led
unsigned long a = 0;
while (1)
{
if (a == 50000)
{
toggleLed(7); // this LED flashes a little quicker than twice per second
stepMotor(0); // output a pulse to the driver to step the motor, attached to PA2
a = 0;
}
a++;
}
}
Appenidx B – The OP’s Original Code – ./drivers/led.c
#include "../headers/stm32f767xx.h"
void initLed(int pin)
{
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN; // enable the GPIOB clock
GPIOB->MODER |= (0x1 << (pin * 2)); // set to output
GPIOB->OTYPER = 0x00; // push-pull mode
GPIOB->ODR = 0x00; // set output register to 0 across all pins
}
void toggleLed(int pin)
{
GPIOB->ODR ^= (0x1 << pin); // toggle the pin
}
---
Appenidx C – The OP’s Original Code – ./drivers/motor.c
---
#include "../headers/stm32f767xx.h"
void initMotor(int step_pin)
{
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN; // enable the GPIOA clock
GPIOA->MODER |= (0x1 << (step_pin * 2)); // set to output
GPIOA->OTYPER = 0x00; // push-pull mode
GPIOA->PUPDR |= (0x2 << (step_pin * 2)); // pull down the pin specified
GPIOA->ODR = 0x00; // set output register to 0 across all pins
}
void stepMotor(int step_pin)
{
GPIOA->ODR |= (1 << step_pin); // output to the pin specified
GPIOA->ODR &= ~(1 << step_pin); // reset the output back to 0
}
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