This is the description of the Python API bindings for the Stepper Brick. General information and technical specifications for the Stepper Brick are summarized in its hardware description.
An installation guide for the Python API bindings is part of their general description.
The example code below is Public Domain (CC0 1.0).
Download (example_configuration.py)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
HOST = "localhost"
PORT = 4223
UID = "a4LCLTYxDK9" # Change to your UID
from tinkerforge.ip_connection import IPConnection
from tinkerforge.brick_stepper import Stepper
if __name__ == "__main__":
ipcon = IPConnection() # Create IP connection
stepper = Stepper(UID, ipcon) # Create device object
ipcon.connect(HOST, PORT) # Connect to brickd
# Don't use device before ipcon is connected
stepper.set_motor_current(800) # 800mA
stepper.set_step_mode(8) # 1/8 step mode
stepper.set_max_velocity(2000) # Velocity 2000 steps/s
# Slow acceleration (500 steps/s^2),
# Fast deacceleration (5000 steps/s^2)
stepper.set_speed_ramping(500, 5000)
stepper.enable()
stepper.set_steps(60000) # Drive 60000 steps forward
raw_input('Press key to exit\n') # Use input() in Python 3
ipcon.disconnect()
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Download (example_callback.py)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
HOST = "localhost"
PORT = 4223
UID = "a4LCLTYxDK9" # Change to your UID
from tinkerforge.ip_connection import IPConnection
from tinkerforge.brick_stepper import Stepper
import random
ipcon = IPConnection() # Create IP connection
stepper = Stepper(UID, ipcon) # Create device object
# Use position reached callback to program random movement
def cb_reached(position):
if random.randint(0, 1):
steps = random.randint(1000, 5000) # steps (forward)
print('Driving forward: ' + str(steps) + ' steps')
else:
steps = random.randint(-5000, -1000) # steps (backward)
print('Driving backward: ' + str(steps) + ' steps')
vel = random.randint(200, 2000) # steps/s
acc = random.randint(100, 1000) # steps/s^2
dec = random.randint(100, 1000) # steps/s^2
print('Configuration (vel, acc, dec): ' + str((vel, acc, dec)))
stepper.set_speed_ramping(acc, dec)
stepper.set_max_velocity(vel)
stepper.set_steps(steps)
if __name__ == "__main__":
ipcon.connect(HOST, PORT) # Connect to brickd
# Don't use device before ipcon is connected
# Register "position reached callback" to cb_reached
# cb_reached will be called every time a position set with
# set_steps or set_target_position is reached
stepper.register_callback(stepper.CALLBACK_POSITION_REACHED, cb_reached)
stepper.enable()
stepper.set_steps(1) # Drive one step forward to get things going
raw_input('Press key to exit\n') # Use input() in Python 3
ipcon.disconnect()
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Generally, every method of the Python bindings can throw an tinkerforge.ip_connection.Error exception that has a value and a description property. value can have different values:
All methods listed below are thread-safe.
Parameters: |
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Creates an object with the unique device ID uid:
stepper = Stepper("YOUR_DEVICE_UID", ipcon)
This object can then be used after the IP Connection is connected (see examples above).
Parameters: | velocity -- int |
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Return type: | None |
Sets the maximum velocity of the stepper motor in steps per second. This function does not start the motor, it merely sets the maximum velocity the stepper motor is accelerated to. To get the motor running use either set_target_position(), set_steps(), drive_forward() or drive_backward().
Return type: | int |
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Returns the velocity as set by set_max_velocity().
Return type: | int |
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Returns the current velocity of the stepper motor in steps per second.
Parameters: |
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Return type: | None |
Sets the acceleration and deacceleration of the stepper motor. The values are given in steps/s². An acceleration of 1000 means, that every second the velocity is increased by 1000 steps/s.
For example: If the current velocity is 0 and you want to accelerate to a velocity of 8000 steps/s in 10 seconds, you should set an acceleration of 800 steps/s².
An acceleration/deacceleration of 0 means instantaneous acceleration/deacceleration (not recommended)
The default value is 1000 for both
Return type: | (int, int) |
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Returns the acceleration and deacceleration as set by set_speed_ramping().
The returned namedtuple has the variables acceleration and deacceleration.
Return type: | None |
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Executes an active full brake.
Warning
This function is for emergency purposes, where an immediate brake is necessary. Depending on the current velocity and the strength of the motor, a full brake can be quite violent.
Call stop() if you just want to stop the motor.
Parameters: | steps -- int |
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Return type: | None |
Sets the number of steps the stepper motor should run. Positive values will drive the motor forward and negative values backward. The velocity, acceleration and deacceleration as set by set_max_velocity() and set_speed_ramping() will be used.
Return type: | int |
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Returns the last steps as set by set_steps().
Return type: | int |
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Returns the remaining steps of the last call of set_steps(). For example, if set_steps() is called with 2000 and get_remaining_steps() is called after the motor has run for 500 steps, it will return 1500.
Return type: | None |
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Drives the stepper motor forward until drive_backward() or stop() is called. The velocity, acceleration and deacceleration as set by set_max_velocity() and set_speed_ramping() will be used.
Return type: | None |
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Drives the stepper motor backward until drive_forward() or stop() is triggered. The velocity, acceleration and deacceleration as set by set_max_velocity() and set_speed_ramping() will be used.
Return type: | None |
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Stops the stepper motor with the deacceleration as set by set_speed_ramping().
Parameters: | current -- int |
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Return type: | None |
Sets the current in mA with which the motor will be driven. The minimum value is 100mA, the maximum value 2291mA and the default value is 800mA.
Warning
Do not set this value above the specifications of your stepper motor. Otherwise it may damage your motor.
Return type: | int |
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Returns the current as set by set_motor_current().
Return type: | None |
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Enables the driver chip. The driver parameters can be configured (maximum velocity, acceleration, etc) before it is enabled.
Return type: | None |
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Disables the driver chip. The configurations are kept (maximum velocity, acceleration, etc) but the motor is not driven until it is enabled again.
Return type: | bool |
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Returns true if the driver chip is enabled, false otherwise.
Parameters: | position -- int |
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Return type: | None |
Sets the current steps of the internal step counter. This can be used to set the current position to 0 when some kind of starting position is reached (e.g. when a CNC machine reaches a corner).
Return type: | int |
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Returns the current position of the stepper motor in steps. On startup the position is 0. The steps are counted with all possible driving functions (set_target_position(), set_steps(), drive_forward() or drive_backward()). It also is possible to reset the steps to 0 or set them to any other desired value with set_current_position().
Parameters: | position -- int |
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Return type: | None |
Sets the target position of the stepper motor in steps. For example, if the current position of the motor is 500 and set_target_position() is called with 1000, the stepper motor will drive 500 steps forward. It will use the velocity, acceleration and deacceleration as set by set_max_velocity() and set_speed_ramping().
A call of set_target_position() with the parameter x is equivalent to a call of set_steps() with the parameter (x - get_current_position()).
Return type: | int |
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Returns the last target position as set by set_target_position().
Parameters: | mode -- int |
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Return type: | None |
Sets the step mode of the stepper motor. Possible values are:
A higher value will increase the resolution and decrease the torque of the stepper motor.
The default value is 8 (Eighth Step).
The following constants are available for this function:
Return type: | int |
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Returns the step mode as set by set_step_mode().
The following constants are available for this function:
Return type: | int |
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Returns the stack input voltage in mV. The stack input voltage is the voltage that is supplied via the stack, i.e. it is given by a Step-Down or Step-Up Power Supply.
Return type: | int |
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Returns the external input voltage in mV. The external input voltage is given via the black power input connector on the Stepper Brick.
If there is an external input voltage and a stack input voltage, the motor will be driven by the external input voltage. If there is only a stack voltage present, the motor will be driven by this voltage.
Warning
This means, if you have a high stack voltage and a low external voltage, the motor will be driven with the low external voltage. If you then remove the external connection, it will immediately be driven by the high stack voltage
Return type: | int |
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Returns the current consumption of the motor in mA.
Parameters: | decay -- int |
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Return type: | None |
Sets the decay mode of the stepper motor. The possible value range is between 0 and 65535. A value of 0 sets the fast decay mode, a value of 65535 sets the slow decay mode and a value in between sets the mixed decay mode.
Changing the decay mode is only possible if synchronous rectification is enabled (see set_sync_rect()).
For a good explanation of the different decay modes see this blog post by Avayan.
A good decay mode is unfortunately different for every motor. The best way to work out a good decay mode for your stepper motor, if you can't measure the current with an oscilloscope, is to listen to the sound of the motor. If the value is too low, you often hear a high pitched sound and if it is too high you can often hear a humming sound.
Generally, fast decay mode (small value) will be noisier but also allow higher motor speeds.
The default value is 10000.
Note
There is unfortunately no formula to calculate a perfect decay mode for a given stepper motor. If you have problems with loud noises or the maximum motor speed is too slow, you should try to tinker with the decay value
Return type: | int |
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Returns the decay mode as set by set_decay().
Parameters: | sync_rect -- bool |
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Return type: | None |
Turns synchronous rectification on or off (true or false).
With synchronous rectification on, the decay can be changed (see set_decay()). Without synchronous rectification fast decay is used.
For an explanation of synchronous rectification see here.
Warning
If you want to use high speeds (> 10000 steps/s) for a large stepper motor with a large inductivity we strongly suggest that you disable synchronous rectification. Otherwise the Brick may not be able to cope with the load and overheat.
The default value is false.
Return type: | bool |
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Returns true if synchronous rectification is enabled, false otherwise.
Parameters: | time_base -- int |
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Return type: | None |
Sets the time base of the velocity and the acceleration of the stepper brick (in seconds).
For example, if you want to make one step every 1.5 seconds, you can set the time base to 15 and the velocity to 10. Now the velocity is 10steps/15s = 1steps/1.5s.
The default value is 1.
Return type: | int |
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Returns the time base as set by set_time_base().
Return type: | (int, int, int, int, int, int) |
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Returns the following parameters: The current velocity, the current position, the remaining steps, the stack voltage, the external voltage and the current consumption of the stepper motor.
There is also a callback for this function, see CALLBACK_ALL_DATA.
The returned namedtuple has the variables current_velocity, current_position, remaining_steps, stack_voltage, external_voltage and current_consumption.
Return type: | [int, int, int] |
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Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.
Parameters: | function_id -- int |
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Return type: | bool |
Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.
For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by set_response_expected(). For setter functions it is disabled by default and can be enabled.
Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.
See set_response_expected() for the list of function ID constants available for this function.
Parameters: |
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Return type: | None |
Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled and callbacks it is always disabled.
Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.
The following function ID constants are available for this function:
Parameters: | response_expected -- bool |
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Return type: | None |
Changes the response expected flag for all setter and callback configuration functions of this device at once.
Return type: | None |
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Enables the status LED.
The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.
The default state is enabled.
New in version 2.3.1 (Firmware).
Return type: | None |
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Disables the status LED.
The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.
The default state is enabled.
New in version 2.3.1 (Firmware).
Return type: | bool |
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Returns true if the status LED is enabled, false otherwise.
New in version 2.3.1 (Firmware).
Parameters: | port -- chr |
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Return type: | (int, [int, int, int], str) |
Returns the firmware and protocol version and the name of the Bricklet for a given port.
This functions sole purpose is to allow automatic flashing of v1.x.y Bricklet plugins.
The returned namedtuple has the variables protocol_version, firmware_version and name.
Return type: | int |
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Returns the temperature in °C/10 as measured inside the microcontroller. The value returned is not the ambient temperature!
The temperature is only proportional to the real temperature and it has an accuracy of +-15%. Practically it is only useful as an indicator for temperature changes.
Return type: | None |
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Calling this function will reset the Brick. Calling this function on a Brick inside of a stack will reset the whole stack.
After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!
Return type: | (str, str, chr, [int, int, int], [int, int, int], int) |
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Returns the UID, the UID where the Brick is connected to, the position, the hardware and firmware version as well as the device identifier.
The position can be '0'-'8' (stack position).
The device identifier numbers can be found here. There is also a constant for the device identifier of this Brick.
The returned namedtuple has the variables uid, connected_uid, position, hardware_version, firmware_version and device_identifier.
Parameters: |
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Return type: | None |
Registers a callback with ID id to the function callback. The available IDs with corresponding function signatures are listed below.
Parameters: | voltage -- int |
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Return type: | None |
Sets the minimum voltage in mV, below which the CALLBACK_UNDER_VOLTAGE callback is triggered. The minimum possible value that works with the Stepper Brick is 8V. You can use this function to detect the discharge of a battery that is used to drive the stepper motor. If you have a fixed power supply, you likely do not need this functionality.
The default value is 8V.
Return type: | int |
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Returns the minimum voltage as set by set_minimum_voltage().
Parameters: | period -- int |
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Return type: | None |
Sets the period in ms with which the CALLBACK_ALL_DATA callback is triggered periodically. A value of 0 turns the callback off.
Return type: | int |
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Returns the period as set by set_all_data_period().
Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the register_callback() function of the device object. The first parameter is the callback ID and the second parameter the callback function:
def my_callback(param):
print(param)
stepper.register_callback(Stepper.CALLBACK_EXAMPLE, my_callback)
The available constants with inherent number and type of parameters are described below.
Note
Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.
Parameters: | voltage -- int |
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This callback is triggered when the input voltage drops below the value set by set_minimum_voltage(). The parameter is the current voltage given in mV.
Parameters: | position -- int |
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This callback is triggered when a position set by set_steps() or set_target_position() is reached.
Note
Since we can't get any feedback from the stepper motor, this only works if the acceleration (see set_speed_ramping()) is set smaller or equal to the maximum acceleration of the motor. Otherwise the motor will lag behind the control value and the callback will be triggered too early.
Parameters: |
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This callback is triggered periodically with the period that is set by set_all_data_period(). The parameters are: the current velocity, the current position, the remaining steps, the stack voltage, the external voltage and the current consumption of the stepper motor.
Parameters: |
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This callback is triggered whenever the Stepper Brick enters a new state. It returns the new state as well as the previous state.
Possible states are:
The following constants are available for this function:
This constant is used to identify a Stepper Brick.
The get_identity() function and the CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.