Description

A micropython library to use stepper motors in a tidy way.

Your steppers should be connected to a stepper driver that is controlled using a step, a dir and optional an enable pin.

This library uses one timer per stepper to achive controlled speeds for multiple steppers in a non blocking way.

The steppers can be controlled by angle if the number of steps per rotation is supplied.

Multiple steppers can share a common dir pin, allowing for N steppers controlled by N+1 output pins.

Install

Place the library in the lib folder of your device (create the folder if it doesn't exist yet).

It should look like this:

• lib
  • stepper
    • __init__.py
    • __main__.py

Examples

Two steppers

fromstepperimportStepperimporttimes1=Stepper(18,19,steps_per_rev=200,speed_sps=50)
s2=Stepper(20,21,steps_per_rev=200,speed_sps=50)
# some boards might require a different timer_id for each stepper:# s1 = Stepper(18,19,steps_per_rev=200,speed_sps=50,timer_id=0)# s2 = Stepper(20,21,steps_per_rev=200,speed_sps=50,timer_id=1)s1.target_deg(90)
s2.target_deg(45)
time.sleep(5.0)
s1.target_deg(0)
s2.target_deg(5)
time.sleep(5.0)

Calibrate absolute position using an endswitch

importmachineimporttimefromstepperimportSteppers1=Stepper(18,19,steps_per_rev=200)
#create an input pin for the end switch (switch connects pin to GND)endswitch=machine.Pin(2, machine.Pin.IN, machine.Pin.PULL_UP)
s1.speed(20) #use low speed for the calibrations1.free_run(-1) #move backwardswhileendswitch.value(): #wait till the switch is triggeredpasss1.stop() #stop as soon as the switch is triggereds1.overwrite_pos(0) #set position as 0 points1.target(0) #set the target to the same value to avoid unwanted movements1.speed(100) #return to default speeds1.track_target() #start stepper again#calibration finished. Do something else below.s1.target_deg(45)
time.sleep(5.0)

Two steppers sharing a common dir pin

importmachinefromstepperimportStepperdir_pin=machine.Pin(19,machine.Pin.OUT)
s1=Stepper(18,dir_pin,steps_per_rev=200,speed_sps=50)
s2=Stepper(20,dir_pin,steps_per_rev=200,speed_sps=50)

API

class Stepper(step_pin,dir_pin,en_pin=None,steps_per_rev=200,speed_sps=10,invert_dir=False,invert_enable=False,timer_id=-1)

• step_pin: Pin id or machine.Pin object for the pin connected to the step input of the stepper driver
• dir_pin: Pin id or machine.Pin object for the pin connected to the direction select input of the stepper driver
• en_pin: (Optional) None or pin id or machine.Pin object for the pin connected to the enable input of the stepper driver
• steps_per_rev: Amount of stepper steps that would result in a 360° rotation
• speed_sps: Speed in steps per secound (= step frequency in Hz)
• invert_dir: True if the direction of the stepper should be inverted
• invert_enable: True if the stepper driver needs an inverted enable signal
• timer_id: Id of the timer that should be used. On most boards -1 will construct a new virtual timer (https://docs.micropython.org/en/latest/library/machine.Timer.html)

speed(sps)

• set the speed of the stepper
• sps: Speed in steps per secound (= step frequency in Hz)

speed_rps(rps)

• set the speed of the stepper
• rps: Speed in rotations per secound

target(t)

• set a target position. The stepper will move towards that position
• t: Target in steps

target_deg(deg)

• set a target position. The stepper will move towards that position
• deg: Target in degrees

target_rad(rad)

• set a target position. The stepper will move towards that position
• rad: Target in radians

get_pos()

• returns the current position in steps

get_pos_deg()

• returns the current position in degrees

get_pos_rad()

• returns the current position in radians

overwrite_pos(p)

• overwrites the current position. Used to calibrate the absolute position
• p: Current position in steps

overwrite_pos_deg(deg)

• overwrites the current position. Used to calibrate the absolute position
• deg: Current position in degree

overwrite_pos_rad(rad)

• overwrites the current position. Used to calibrate the absolute position
• rad: Current position in radians

step(d)

• instantly moves the stepper by a single step
• d: Direction of the step (d>0: Forwards, d<0: Backwards, d==0: No movement)

free_run(d)

• moves the stepper continuously until stopped
• d: Direction of movement (d>0: Forwards, d<0: Backwards, d==0: Stop)

track_target()

• puts the stepper back in the default mode, where it follows the target position after free_run(d) or stop() was used.

stop()

• stops the timer and all movement (single steps using the step() function are still possible)

enable(e)

• enable or disable the stepper driver using the enable pin. While this stops the movement of the actual hardware, the Stepper class will still act as if the stepper is moving. This can be used for testing. Recalibration of the absolute position might be needed if the stepper was disabled. -e: True or False

is_enabled()

• returns the last status (True or False) of the enable(e) function

is_target_reached()

• returns if the target position is reached (True or False)