This is the description of the Python API bindings for the DC Bricklet 2.0. General information and technical specifications for the DC Bricklet 2.0 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 31 32 33 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your DC Bricklet 2.0
import time
from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_dc_v2 import BrickletDCV2
if __name__ == "__main__":
ipcon = IPConnection() # Create IP connection
dc = BrickletDCV2(UID, ipcon) # Create device object
ipcon.connect(HOST, PORT) # Connect to brickd
# Don't use device before ipcon is connected
dc.set_drive_mode(dc.DRIVE_MODE_DRIVE_COAST)
dc.set_pwm_frequency(10000) # Use PWM frequency of 10 kHz
dc.set_motion(4096,
16384) # Slow acceleration (12.5 %/s), fast decceleration (50 %/s) for stopping
dc.set_velocity(32767) # Full speed forward (100 %)
dc.set_enabled(True) # Enable motor power
input("Press key to exit\n") # Use raw_input() in Python 2
dc.set_velocity(0) # Stop motor before disabling motor power
time.sleep(2) # Wait for motor to actually stop: velocity (100 %) / decceleration (50 %/s) = 2 s
dc.set_enabled(False) # Disable motor power
ipcon.disconnect()
|
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 48 49 50 51 52 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your DC Bricklet 2.0
import time
from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_dc_v2 import BrickletDCV2
# Use velocity reached callback to swing back and forth
# between full speed forward and full speed backward
def cb_velocity_reached(velocity, dc):
if velocity == 32767:
print('Velocity: Full speed forward, now turning backward')
dc.set_velocity(-32767)
elif velocity == -32767:
print('Velocity: Full speed backward, now turning forward')
dc.set_velocity(32767)
else:
print('Error') # Can only happen if another program sets velocity
if __name__ == "__main__":
ipcon = IPConnection() # Create IP connection
dc = BrickletDCV2(UID, ipcon) # Create device object
ipcon.connect(HOST, PORT) # Connect to brickd
# Don't use device before ipcon is connected
# The acceleration has to be smaller or equal to the maximum
# acceleration of the DC motor, otherwise the velocity reached
# callback will be called too early
dc.set_motion(4096,
16384) # Slow acceleration (12.5 %/s), fast decceleration (50 %/s) for stopping
dc.set_velocity(32767) # Full speed forward (100 %)
# Register velocity reached callback to function cb_velocity_reached
dc.register_callback(dc.CALLBACK_VELOCITY_REACHED,
lambda x: cb_velocity_reached(x, dc))
# Enable motor power
dc.set_enabled(True)
input("Press key to exit\n") # Use raw_input() in Python 2
dc.set_velocity(0) # Stop motor before disabling motor power
time.sleep(2) # Wait for motor to actually stop: velocity (100 %) / decceleration (50 %/s) = 2 s
dc.set_enabled(False) # Disable motor power
ipcon.disconnect()
|
Generally, every function 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 functions listed below are thread-safe.
BrickletDCV2
(uid, ipcon)¶Parameters: |
|
---|---|
Returns: |
|
Creates an object with the unique device ID uid
:
dc_v2 = BrickletDCV2("YOUR_DEVICE_UID", ipcon)
This object can then be used after the IP Connection is connected.
BrickletDCV2.
set_enabled
(enabled)¶Parameters: |
|
---|---|
Returns: |
|
Enables/Disables the driver chip. The driver parameters can be configured (velocity, acceleration, etc) before it is enabled.
BrickletDCV2.
get_enabled
()¶Returns: |
|
---|
Returns true if the driver chip is enabled, false otherwise.
BrickletDCV2.
set_velocity
(velocity)¶Parameters: |
|
---|---|
Returns: |
|
Sets the velocity of the motor. Whereas -32767 is full speed backward,
0 is stop and 32767 is full speed forward. Depending on the
acceleration (see set_motion()
), the motor is not immediately
brought to the velocity but smoothly accelerated.
The velocity describes the duty cycle of the PWM with which the motor is
controlled, e.g. a velocity of 3277 sets a PWM with a 10% duty cycle.
You can not only control the duty cycle of the PWM but also the frequency,
see set_pwm_frequency()
.
BrickletDCV2.
get_velocity
()¶Returns: |
|
---|
Returns the velocity as set by set_velocity()
.
BrickletDCV2.
get_current_velocity
()¶Returns: |
|
---|
Returns the current velocity of the motor. This value is different
from get_velocity()
whenever the motor is currently accelerating
to a goal set by set_velocity()
.
BrickletDCV2.
set_motion
(acceleration, deceleration)¶Parameters: |
|
---|---|
Returns: |
|
Sets the acceleration and deceleration of the motor. It is given in velocity/s. An acceleration of 10000 means, that every second the velocity is increased by 10000 (or about 30% duty cycle).
For example: If the current velocity is 0 and you want to accelerate to a velocity of 16000 (about 50% duty cycle) in 10 seconds, you should set an acceleration of 1600.
If acceleration and deceleration is set to 0, there is no speed ramping, i.e. a new velocity is immediately given to the motor.
BrickletDCV2.
get_motion
()¶Return Object: |
|
---|
Returns the acceleration/deceleration as set by set_motion()
.
BrickletDCV2.
full_brake
()¶Returns: |
|
---|
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 set_velocity()
with 0 if you just want to stop the motor.
BrickletDCV2.
get_pwm_frequency
()¶Returns: |
|
---|
Returns the PWM frequency as set by set_pwm_frequency()
.
BrickletDCV2.
get_power_statistics
()¶Return Object: |
|
---|
Returns input voltage and current usage of the driver.
BrickletDCV2.
set_drive_mode
(mode)¶Parameters: |
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---|---|
Returns: |
|
Sets the drive mode. Possible modes are:
These modes are different kinds of motor controls.
In Drive/Brake mode, the motor is always either driving or braking. There is no freewheeling. Advantages are: A more linear correlation between PWM and velocity, more exact accelerations and the possibility to drive with slower velocities.
In Drive/Coast mode, the motor is always either driving or freewheeling. Advantages are: Less current consumption and less demands on the motor and driver chip.
The following constants are available for this function:
For mode:
BrickletDCV2.
get_drive_mode
()¶Returns: |
|
---|
Returns the drive mode, as set by set_drive_mode()
.
The following constants are available for this function:
For mode:
BrickletDCV2.
set_pwm_frequency
(frequency)¶Parameters: |
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---|---|
Returns: |
|
Sets the frequency of the PWM with which the motor is driven. Often a high frequency is less noisy and the motor runs smoother. However, with a low frequency there are less switches and therefore fewer switching losses. Also with most motors lower frequencies enable higher torque.
If you have no idea what all this means, just ignore this function and use the default frequency, it will very likely work fine.
BrickletDCV2.
set_error_led_config
(config)¶Parameters: |
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---|---|
Returns: |
|
Configures the error LED to be either turned off, turned on, blink in heartbeat mode or show an error.
If the LED is configured to show errors it has three different states:
The following constants are available for this function:
For config:
BrickletDCV2.
get_error_led_config
()¶Returns: |
|
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Returns the LED configuration as set by set_error_led_config()
The following constants are available for this function:
For config:
BrickletDCV2.
get_spitfp_error_count
()¶Return Object: |
|
---|
Returns the error count for the communication between Brick and Bricklet.
The errors are divided into
The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.
BrickletDCV2.
set_status_led_config
(config)¶Parameters: |
|
---|---|
Returns: |
|
Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.
You can also turn the LED permanently on/off or show a heartbeat.
If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.
The following constants are available for this function:
For config:
BrickletDCV2.
get_status_led_config
()¶Returns: |
|
---|
Returns the configuration as set by set_status_led_config()
The following constants are available for this function:
For config:
BrickletDCV2.
get_chip_temperature
()¶Returns: |
|
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Returns the temperature 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 bad accuracy. Practically it is only useful as an indicator for temperature changes.
BrickletDCV2.
reset
()¶Returns: |
|
---|
Calling this function will reset the Bricklet. All configurations will be lost.
After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!
BrickletDCV2.
get_identity
()¶Return Object: |
|
---|
Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.
The position can be 'a', 'b', 'c', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.
The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.
BrickletDCV2.
register_callback
(callback_id, function)¶Parameters: |
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---|---|
Returns: |
|
Registers the given function
with the given callback_id
.
The available callback IDs with corresponding function signatures are listed below.
BrickletDCV2.
set_emergency_shutdown_callback_configuration
(enabled)¶Parameters: |
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---|---|
Returns: |
|
Enable/Disable CALLBACK_EMERGENCY_SHUTDOWN
callback.
BrickletDCV2.
get_emergency_shutdown_callback_configuration
()¶Returns: |
|
---|
Returns the callback configuration as set by
set_emergency_shutdown_callback_configuration()
.
BrickletDCV2.
set_velocity_reached_callback_configuration
(enabled)¶Parameters: |
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---|---|
Returns: |
|
Enable/Disable CALLBACK_VELOCITY_REACHED
callback.
BrickletDCV2.
get_velocity_reached_callback_configuration
()¶Returns: |
|
---|
Returns the callback configuration as set by
set_velocity_reached_callback_configuration()
.
BrickletDCV2.
set_current_velocity_callback_configuration
(period, value_has_to_change)¶Parameters: |
|
---|---|
Returns: |
|
The period is the period with which the CALLBACK_CURRENT_VELOCITY
callback is triggered periodically. A value of 0 turns the callback off.
If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.
If it is set to false, the callback is continuously triggered with the period, independent of the value.
BrickletDCV2.
get_current_velocity_callback_configuration
()¶Return Object: |
|
---|
Returns the callback configuration as set by
set_current_velocity_callback_configuration()
.
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)
dc_v2.register_callback(BrickletDCV2.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.
BrickletDCV2.
CALLBACK_EMERGENCY_SHUTDOWN
¶Callback Parameters: |
|
---|
This callback is triggered if either the current consumption is too high (above 5A) or the temperature of the driver chip is too high (above 175°C). These two possibilities are essentially the same, since the temperature will reach this threshold immediately if the motor consumes too much current. In case of a voltage below 3.3V (external or stack) this callback is triggered as well.
If this callback is triggered, the driver chip gets disabled at the same time.
That means, set_enabled()
has to be called to drive the motor again.
Note
This callback only works in Drive/Brake mode (see set_drive_mode()
). In
Drive/Coast mode it is unfortunately impossible to reliably read the
overcurrent/overtemperature signal from the driver chip.
BrickletDCV2.
CALLBACK_VELOCITY_REACHED
¶Callback Parameters: |
|
---|
This callback is triggered whenever a set velocity is reached. For example:
If a velocity of 0 is present, acceleration is set to 5000 and velocity
to 10000, the CALLBACK_VELOCITY_REACHED
callback will be triggered after about
2 seconds, when the set velocity is actually reached.
Note
Since we can't get any feedback from the DC motor, this only works if the
acceleration (see set_motion()
) 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.
BrickletDCV2.
CALLBACK_CURRENT_VELOCITY
¶Callback Parameters: |
|
---|
This callback is triggered with the period that is set by
set_current_velocity_callback_configuration()
. The parameter is the current
velocity used by the motor.
The CALLBACK_CURRENT_VELOCITY
callback is only triggered after the set period
if there is a change in the velocity.
Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.
BrickletDCV2.
get_api_version
()¶Return Object: |
|
---|
Returns the version of the API definition 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.
BrickletDCV2.
get_response_expected
(function_id)¶Parameters: |
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---|---|
Returns: |
|
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 sent and errors are silently ignored, because they cannot be detected.
The following constants are available for this function:
For function_id:
BrickletDCV2.
set_response_expected
(function_id, response_expected)¶Parameters: |
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---|---|
Returns: |
|
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.
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 sent and errors are silently ignored, because they cannot be detected.
The following constants are available for this function:
For function_id:
BrickletDCV2.
set_response_expected_all
(response_expected)¶Parameters: |
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---|---|
Returns: |
|
Changes the response expected flag for all setter and callback configuration functions of this device at once.
Internal functions are used for maintenance tasks such as flashing a new firmware of changing the UID of a Bricklet. These task should be performed using Brick Viewer instead of using the internal functions directly.
BrickletDCV2.
set_bootloader_mode
(mode)¶Parameters: |
|
---|---|
Returns: |
|
Sets the bootloader mode and returns the status after the requested mode change was instigated.
You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.
This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.
The following constants are available for this function:
For mode:
For status:
BrickletDCV2.
get_bootloader_mode
()¶Returns: |
|
---|
Returns the current bootloader mode, see set_bootloader_mode()
.
The following constants are available for this function:
For mode:
BrickletDCV2.
set_write_firmware_pointer
(pointer)¶Parameters: |
|
---|---|
Returns: |
|
Sets the firmware pointer for write_firmware()
. The pointer has
to be increased by chunks of size 64. The data is written to flash
every 4 chunks (which equals to one page of size 256).
This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.
BrickletDCV2.
write_firmware
(data)¶Parameters: |
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---|---|
Returns: |
|
Writes 64 Bytes of firmware at the position as written by
set_write_firmware_pointer()
before. The firmware is written
to flash every 4 chunks.
You can only write firmware in bootloader mode.
This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.
BrickletDCV2.
write_uid
(uid)¶Parameters: |
|
---|---|
Returns: |
|
Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.
We recommend that you use Brick Viewer to change the UID.
BrickletDCV2.
read_uid
()¶Returns: |
|
---|
Returns the current UID as an integer. Encode as Base58 to get the usual string version.
BrickletDCV2.
DEVICE_IDENTIFIER
¶This constant is used to identify a DC Bricklet 2.0.
The get_identity()
function and the
IPConnection.CALLBACK_ENUMERATE
callback of the IP Connection have a device_identifier
parameter to specify
the Brick's or Bricklet's type.
BrickletDCV2.
DEVICE_DISPLAY_NAME
¶This constant represents the human readable name of a DC Bricklet 2.0.