stepper.py

# Stepper Motors on Raspberry Pi
from time import monotonic, sleep
from gpiozero import OutputDevice

class Stepper:
    """
    Class to control a stepper motor connected to the GPIO pins.

    Args:
        number_of_steps: The number of steps per revolution for the motor. If
                         the value is given as the number of degrees per step,
                         then divide 360 by that number to get the number of
                         steps (for example, 360 / 1.8 gives 200 steps).
        motor_pins: The GPIO pins to use to control the motor.
    """

    def __init__(self, number_of_steps, *motor_pins):
        self.step_number = 0
        self.steps_left = 0
        self.direction = 0
        self.last_step_time = 0
        self.number_of_steps = number_of_steps
        self.step_delay = 0
        self.pin_count = len(motor_pins)
        if self.pin_count not in (2, 4, 5):
            raise ValueError("Unsupported number of pins. Use 2, 4, or 5 pins.")

        self.pins = [OutputDevice(pin) for pin in motor_pins]
        
        self.motor_pin_1 = self.pins[0]
        self.motor_pin_2 = self.pins[1]
        if self.pin_count >= 4:
            self.motor_pin_3 = self.pins[2]
            self.motor_pin_4 = self.pins[3]      
        if self.pin_count == 5:
            self.motor_pin_5 = self.pins[4]

    def set_speed(self, speed):
        """
        Sets the speed of the motor. This does not move the motor, just
        specifies how fast it moves when you call `step()`.

        Args:
            speed: The motor speed in rotations per minute (RPM).
        """

        if speed <= 0:
            return
        self.step_delay = 60.0 / (self.number_of_steps * speed)

    def step(self, steps_to_move):
        """
        Make the motor turn the specified number of steps. The speed of
        the steps is determined by the most recent call of `speed()`.

        Note: this function is blocking; it does not return until all 
        the steps have been completed, which could be a long time for
        a large number of steps (or a low speed).

        Args:
            steps_to_move: The number of steps to turn. A negative value turns
                           in the opposite direction.
        """

        self.start(steps_to_move)
        while self.steps_left > 0:
            t = self.tick()
            sleep(max(t, 0.0001))

    def start(self, steps_to_move):
        """
        Begin the motor turn the specified number of steps. The speed of
        the steps is determined by the most recent call of `speed()`.

        Note: this function only initiates the movement; the motor will 
        only actually move when tick() method is called

        Args:
            steps_to_move: The number of steps to turn. A negative value turns
                           in the opposite direction.
        """        

        self.direction = 1 if steps_to_move > 0 else -1
        self.steps_left = abs(steps_to_move)
        self.last_step_time = 0

    def tick(self):
        """Call this inside the main loop each iteration frequently enough."""
        if self.steps_left <= 0:
            return 0.0
        current_time = monotonic()
        target_time = self.last_step_time + self.step_delay
        if current_time >= target_time:
            self.last_step_time = current_time
            self.step_number += self.direction
            self.step_number %= self.number_of_steps
            self.step_motor(self.step_number % (10 if self.pin_count == 5 else 4))
            self.steps_left -= 1
            return 0.0
        return target_time - current_time

    def step_motor(self, cur_step):
        """
        Internal method to implement a single step by toggling the GPIO pins.
        """

        if self.pin_count == 2:
            if cur_step == 0:    # 01
                self.motor_pin_1.off()
                self.motor_pin_2.on()
            elif cur_step == 1:  # 11
                self.motor_pin_1.on()
                self.motor_pin_2.on()
            elif cur_step == 2:  # 10
                self.motor_pin_1.on()
                self.motor_pin_2.off()
            elif cur_step == 3:  # 00
                self.motor_pin_1.off()
                self.motor_pin_2.off()
        elif self.pin_count == 4:
            if cur_step == 0:    # 1010
                self.motor_pin_1.on()
                self.motor_pin_2.off()
                self.motor_pin_3.on()
                self.motor_pin_4.off()
            elif cur_step == 1:  # 0110
                self.motor_pin_1.off()
                self.motor_pin_2.on()
                self.motor_pin_3.on()
                self.motor_pin_4.off()
            elif cur_step == 2:  # 0101
                self.motor_pin_1.off()
                self.motor_pin_2.on()
                self.motor_pin_3.off()
                self.motor_pin_4.on()
            elif cur_step == 3:  # 1001
                self.motor_pin_1.on()
                self.motor_pin_2.off()
                self.motor_pin_3.off()
                self.motor_pin_4.on()
        elif self.pin_count == 5:
            if cur_step == 0:    # 01101
                self.motor_pin_1.off()
                self.motor_pin_2.on()
                self.motor_pin_3.on()
                self.motor_pin_4.off()
                self.motor_pin_5.on()
            elif cur_step == 1:  # 01001
                self.motor_pin_1.off()
                self.motor_pin_2.on()
                self.motor_pin_3.off()
                self.motor_pin_4.off()
                self.motor_pin_5.on()
            elif cur_step == 2:  # 01011
                self.motor_pin_1.off()
                self.motor_pin_2.on()
                self.motor_pin_3.off()
                self.motor_pin_4.on()
                self.motor_pin_5.on()
            elif cur_step == 3:  # 01010
                self.motor_pin_1.off()
                self.motor_pin_2.on()
                self.motor_pin_3.off()
                self.motor_pin_4.on()
                self.motor_pin_5.off()
            elif cur_step == 4:  # 11010
                self.motor_pin_1.on()
                self.motor_pin_2.on()
                self.motor_pin_3.off()
                self.motor_pin_4.on()
                self.motor_pin_5.off()
            elif cur_step == 5:  # 10010
                self.motor_pin_1.on()
                self.motor_pin_2.off()
                self.motor_pin_3.off()
                self.motor_pin_4.on()
                self.motor_pin_5.off()
            elif cur_step == 6:  # 10110
                self.motor_pin_1.on()
                self.motor_pin_2.off()
                self.motor_pin_3.on()
                self.motor_pin_4.on()
                self.motor_pin_5.off()
            elif cur_step == 7:  # 10100
                self.motor_pin_1.on()
                self.motor_pin_2.off()
                self.motor_pin_3.on()
                self.motor_pin_4.off()
                self.motor_pin_5.off()
            elif cur_step == 8:  # 10101
                self.motor_pin_1.on()
                self.motor_pin_2.off()
                self.motor_pin_3.on()
                self.motor_pin_4.off()
                self.motor_pin_5.on()
            elif cur_step == 9:  # 00101
                self.motor_pin_1.off()
                self.motor_pin_2.off()
                self.motor_pin_3.on()
                self.motor_pin_4.off()
                self.motor_pin_5.on()

    def stop(self):
        """
        Stop the motor by setting all the GPIO pins low.
        """

        self.steps_left = 0
        for pin in self.pins:
            pin.off()