Perl - Servo Brick

This is the description of the Perl API bindings for the Servo Brick. General information and technical specifications for the Servo Brick are summarized in its hardware description.

An installation guide for the Perl API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Configuration

Download (example_configuration.pl)

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#!/usr/bin/perl

use strict;
use Tinkerforge::IPConnection;
use Tinkerforge::BrickServo;

use constant HOST => 'localhost';
use constant PORT => 4223;
use constant UID => 'XXYYZZ'; # Change XXYYZZ to the UID of your Servo Brick

my $ipcon = Tinkerforge::IPConnection->new(); # Create IP connection
my $servo = Tinkerforge::BrickServo->new(&UID, $ipcon); # Create device object

$ipcon->connect(&HOST, &PORT); # Connect to brickd
# Don't use device before ipcon is connected

# Configure two servos with voltage 5.5V
# Servo 1: Connected to port 0, period of 19.5ms, pulse width of 1 to 2ms
#          and operating angle -100 to 100°
#
# Servo 2: Connected to port 5, period of 20ms, pulse width of 0.95
#          to 1.95ms and operating angle -90 to 90°
$servo->set_output_voltage(5500);

$servo->set_degree(0, -10000, 10000);
$servo->set_pulse_width(0, 1000, 2000);
$servo->set_period(0, 19500);
$servo->set_acceleration(0, 1000); # Slow acceleration
$servo->set_velocity(0, 65535); # Full speed

$servo->set_degree(5, -9000, 9000);
$servo->set_pulse_width(5, 950, 1950);
$servo->set_period(5, 20000);
$servo->set_acceleration(5, 65535); # Full acceleration
$servo->set_velocity(5, 65535); # Full speed

$servo->set_position(0, 10000); # Set to most right position
$servo->enable(0);

$servo->set_position(5, -9000); # Set to most left position
$servo->enable(5);

print "Press key to exit\n";
<STDIN>;
$servo->disable(0);
$servo->disable(5);
$ipcon->disconnect();

Callback

Download (example_callback.pl)

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#!/usr/bin/perl

use strict;
use Tinkerforge::IPConnection;
use Tinkerforge::BrickServo;

use constant HOST => 'localhost';
use constant PORT => 4223;
use constant UID => 'XXYYZZ'; # Change XXYYZZ to the UID of your Servo Brick

my $ipcon = Tinkerforge::IPConnection->new(); # Create IP connection
our $servo = Tinkerforge::BrickServo->new(&UID, $ipcon); # Create device object

# Use position reached callback to swing back and forth
sub cb_position_reached
{
    my ($servo_num, $position) = @_;

    if ($position == 9000)
    {
        print "Position: 90°, going to -90°\n";
        $servo->set_position($servo_num, -9000);
    }
    elsif ($position == -9000)
    {
        print "Position: -90°, going to 90°\n";
        $servo->set_position($servo_num, 9000);
    }
    else
    {
        print "Error\n"; # Can only happen if another program sets position
    }
}

$ipcon->connect(&HOST, &PORT); # Connect to brickd
# Don't use device before ipcon is connected

# Register position reached callback to subroutine cb_position_reached
$servo->register_callback($servo->CALLBACK_POSITION_REACHED, 'cb_position_reached');

# Enable position reached callback
$servo->enable_position_reached_callback();

# Set velocity to 100°/s. This has to be smaller or equal to the
# maximum velocity of the servo you are using, otherwise the position
# reached callback will be called too early
$servo->set_velocity(0, 10000);
$servo->set_position(0, 9000);
$servo->enable(0);

print "Press key to exit\n";
<STDIN>;
$servo->disable(0);
$ipcon->disconnect();

API

Generally, every subroutine of the Perl bindings can report an error as Tinkerforge::Error object via croak(). The object has a get_code() and a get_message() subroutine. There are different error code:

  • Error->ALREADY_CONNECTED = 11
  • Error->NOT_CONNECTED = 12
  • Error->CONNECT_FAILED = 13
  • Error->INVALID_FUNCTION_ID = 21
  • Error->TIMEOUT = 31
  • Error->INVALID_PARAMETER = 41
  • Error->FUNCTION_NOT_SUPPORTED = 42
  • Error->UNKNOWN_ERROR = 43

All methods listed below are thread-safe.

Every function of the Servo Brick API that has a servo_num parameter can address a servo with the servo number (0 to 6). If it is a setter function then multiple servos can be addressed at once with a bitmask for the servos, if the highest bit is set. For example: 1 will address servo 1, (1 << 1) | (1 << 5) | (1 << 7) will address servos 1 and 5, 0xFF will address all seven servos, etc. This allows to set configurations to several servos with one function call. It is guaranteed that the changes will take effect in the same PWM period for all servos you specified in the bitmask.

Basic Functions

BrickServo->new($uid, $ipcon)
Parameters:
  • $uid -- string
  • $ipcon -- IPConnection
Return type:

BrickServo

Creates an object with the unique device ID $uid:

$servo = BrickServo->new("YOUR_DEVICE_UID", $ipcon);

This object can then be used after the IP Connection is connected (see examples above).

BrickServo->enable($servo_num)
Parameters:$servo_num -- int
Return type:undef

Enables a servo (0 to 6). If a servo is enabled, the configured position, velocity, acceleration, etc. are applied immediately.

BrickServo->disable($servo_num)
Parameters:$servo_num -- int
Return type:undef

Disables a servo (0 to 6). Disabled servos are not driven at all, i.e. a disabled servo will not hold its position if a load is applied.

BrickServo->is_enabled($servo_num)
Parameters:$servo_num -- int
Return type:bool

Returns true if the specified servo is enabled, false otherwise.

BrickServo->set_position($servo_num, $position)
Parameters:
  • $servo_num -- int
  • $position -- int
Return type:

undef

Sets the position in °/100 for the specified servo.

The default range of the position is -9000 to 9000, but it can be specified according to your servo with set_degree().

If you want to control a linear servo or RC brushless motor controller or similar with the Servo Brick, you can also define lengths or speeds with set_degree().

BrickServo->get_position($servo_num)
Parameters:$servo_num -- int
Return type:int

Returns the position of the specified servo as set by set_position().

BrickServo->get_current_position($servo_num)
Parameters:$servo_num -- int
Return type:int

Returns the current position of the specified servo. This may not be the value of set_position() if the servo is currently approaching a position goal.

BrickServo->set_velocity($servo_num, $velocity)
Parameters:
  • $servo_num -- int
  • $velocity -- int
Return type:

undef

Sets the maximum velocity of the specified servo in °/100s. The velocity is accelerated according to the value set by set_acceleration().

The minimum velocity is 0 (no movement) and the maximum velocity is 65535. With a value of 65535 the position will be set immediately (no velocity).

The default value is 65535.

BrickServo->get_velocity($servo_num)
Parameters:$servo_num -- int
Return type:int

Returns the velocity of the specified servo as set by set_velocity().

BrickServo->get_current_velocity($servo_num)
Parameters:$servo_num -- int
Return type:int

Returns the current velocity of the specified servo. This may not be the value of set_velocity() if the servo is currently approaching a velocity goal.

BrickServo->set_acceleration($servo_num, $acceleration)
Parameters:
  • $servo_num -- int
  • $acceleration -- int
Return type:

undef

Sets the acceleration of the specified servo in °/100s².

The minimum acceleration is 1 and the maximum acceleration is 65535. With a value of 65535 the velocity will be set immediately (no acceleration).

The default value is 65535.

BrickServo->get_acceleration($servo_num)
Parameters:$servo_num -- int
Return type:int

Returns the acceleration for the specified servo as set by set_acceleration().

BrickServo->set_output_voltage($voltage)
Parameters:$voltage -- int
Return type:undef

Sets the output voltages with which the servos are driven in mV. The minimum output voltage is 2000mV and the maximum output voltage is 9000mV.

Note

We recommend that you set this value to the maximum voltage that is specified for your servo, most servos achieve their maximum force only with high voltages.

The default value is 5000.

BrickServo->get_output_voltage()
Return type:int

Returns the output voltage as specified by set_output_voltage().

BrickServo->set_pulse_width($servo_num, $min, $max)
Parameters:
  • $servo_num -- int
  • $min -- int
  • $max -- int
Return type:

undef

Sets the minimum and maximum pulse width of the specified servo in µs.

Usually, servos are controlled with a PWM, whereby the length of the pulse controls the position of the servo. Every servo has different minimum and maximum pulse widths, these can be specified with this function.

If you have a datasheet for your servo that specifies the minimum and maximum pulse width, you should set the values accordingly. If your servo comes without any datasheet you have to find the values via trial and error.

Both values have a range from 1 to 65535 (unsigned 16-bit integer). The minimum must be smaller than the maximum.

The default values are 1000µs (1ms) and 2000µs (2ms) for minimum and maximum pulse width.

BrickServo->get_pulse_width($servo_num)
Parameters:$servo_num -- int
Return type:[int, int]

Returns the minimum and maximum pulse width for the specified servo as set by set_pulse_width().

The returned array contains the elements min and max.

BrickServo->set_degree($servo_num, $min, $max)
Parameters:
  • $servo_num -- int
  • $min -- int
  • $max -- int
Return type:

undef

Sets the minimum and maximum degree for the specified servo (by default given as °/100).

This only specifies the abstract values between which the minimum and maximum pulse width is scaled. For example: If you specify a pulse width of 1000µs to 2000µs and a degree range of -90° to 90°, a call of set_position() with 0 will result in a pulse width of 1500µs (-90° = 1000µs, 90° = 2000µs, etc.).

Possible usage:

  • The datasheet of your servo specifies a range of 200° with the middle position at 110°. In this case you can set the minimum to -9000 and the maximum to 11000.
  • You measure a range of 220° on your servo and you don't have or need a middle position. In this case you can set the minimum to 0 and the maximum to 22000.
  • You have a linear servo with a drive length of 20cm, In this case you could set the minimum to 0 and the maximum to 20000. Now you can set the Position with set_position() with a resolution of cm/100. Also the velocity will have a resolution of cm/100s and the acceleration will have a resolution of cm/100s².
  • You don't care about units and just want the highest possible resolution. In this case you should set the minimum to -32767 and the maximum to 32767.
  • You have a brushless motor with a maximum speed of 10000 rpm and want to control it with a RC brushless motor controller. In this case you can set the minimum to 0 and the maximum to 10000. set_position() now controls the rpm.

Both values have a possible range from -32767 to 32767 (signed 16-bit integer). The minimum must be smaller than the maximum.

The default values are -9000 and 9000 for the minimum and maximum degree.

BrickServo->get_degree($servo_num)
Parameters:$servo_num -- int
Return type:[int, int]

Returns the minimum and maximum degree for the specified servo as set by set_degree().

The returned array contains the elements min and max.

BrickServo->set_period($servo_num, $period)
Parameters:
  • $servo_num -- int
  • $period -- int
Return type:

undef

Sets the period of the specified servo in µs.

Usually, servos are controlled with a PWM. Different servos expect PWMs with different periods. Most servos run well with a period of about 20ms.

If your servo comes with a datasheet that specifies a period, you should set it accordingly. If you don't have a datasheet and you have no idea what the correct period is, the default value (19.5ms) will most likely work fine.

The minimum possible period is 1µs and the maximum is 65535µs.

The default value is 19.5ms (19500µs).

BrickServo->get_period($servo_num)
Parameters:$servo_num -- int
Return type:int

Returns the period for the specified servo as set by set_period().

BrickServo->get_servo_current($servo_num)
Parameters:$servo_num -- int
Return type:int

Returns the current consumption of the specified servo in mA.

BrickServo->get_overall_current()
Return type:int

Returns the current consumption of all servos together in mA.

BrickServo->get_stack_input_voltage()
Return type:int

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.

BrickServo->get_external_input_voltage()
Return type:int

Returns the external input voltage in mV. The external input voltage is given via the black power input connector on the Servo Brick.

If there is an external input voltage and a stack input voltage, the motors will be driven by the external input voltage. If there is only a stack voltage present, the motors will be driven by this voltage.

Warning

This means, if you have a high stack voltage and a low external voltage, the motors 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

Advanced Functions

BrickServo->get_api_version()
Return type:[int, int, int]

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.

BrickServo->get_response_expected($function_id)
Parameters:$function_id -- int
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.

BrickServo->set_response_expected($function_id, $response_expected)
Parameters:
  • $function_id -- int
  • $response_expected -- bool
Return type:

undef

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 send and errors are silently ignored, because they cannot be detected.

The following function ID constants are available for this function:

  • BrickServo->FUNCTION_ENABLE = 1
  • BrickServo->FUNCTION_DISABLE = 2
  • BrickServo->FUNCTION_SET_POSITION = 4
  • BrickServo->FUNCTION_SET_VELOCITY = 7
  • BrickServo->FUNCTION_SET_ACCELERATION = 10
  • BrickServo->FUNCTION_SET_OUTPUT_VOLTAGE = 12
  • BrickServo->FUNCTION_SET_PULSE_WIDTH = 14
  • BrickServo->FUNCTION_SET_DEGREE = 16
  • BrickServo->FUNCTION_SET_PERIOD = 18
  • BrickServo->FUNCTION_SET_MINIMUM_VOLTAGE = 24
  • BrickServo->FUNCTION_ENABLE_POSITION_REACHED_CALLBACK = 29
  • BrickServo->FUNCTION_DISABLE_POSITION_REACHED_CALLBACK = 30
  • BrickServo->FUNCTION_ENABLE_VELOCITY_REACHED_CALLBACK = 32
  • BrickServo->FUNCTION_DISABLE_VELOCITY_REACHED_CALLBACK = 33
  • BrickServo->FUNCTION_SET_SPITFP_BAUDRATE_CONFIG = 231
  • BrickServo->FUNCTION_SET_SPITFP_BAUDRATE = 234
  • BrickServo->FUNCTION_ENABLE_STATUS_LED = 238
  • BrickServo->FUNCTION_DISABLE_STATUS_LED = 239
  • BrickServo->FUNCTION_RESET = 243
BrickServo->set_response_expected_all($response_expected)
Parameters:$response_expected -- bool
Return type:undef

Changes the response expected flag for all setter and callback configuration functions of this device at once.

BrickServo->set_spitfp_baudrate_config($enable_dynamic_baudrate, $minimum_dynamic_baudrate)
Parameters:
  • $enable_dynamic_baudrate -- bool
  • $minimum_dynamic_baudrate -- int
Return type:

undef

The SPITF protocol can be used with a dynamic baudrate. If the dynamic baudrate is enabled, the Brick will try to adapt the baudrate for the communication between Bricks and Bricklets according to the amount of data that is transferred.

The baudrate will be increased exponentially if lots of data is send/received and decreased linearly if little data is send/received.

This lowers the baudrate in applications where little data is transferred (e.g. a weather station) and increases the robustness. If there is lots of data to transfer (e.g. Thermal Imaging Bricklet) it automatically increases the baudrate as needed.

In cases where some data has to transferred as fast as possible every few seconds (e.g. RS485 Bricklet with a high baudrate but small payload) you may want to turn the dynamic baudrate off to get the highest possible performance.

The maximum value of the baudrate can be set per port with the function set_spitfp_baudrate(). If the dynamic baudrate is disabled, the baudrate as set by set_spitfp_baudrate() will be used statically.

The minimum dynamic baudrate has a value range of 400000 to 2000000 baud.

By default dynamic baudrate is enabled and the minimum dynamic baudrate is 400000.

New in version 2.3.4 (Firmware).

BrickServo->get_spitfp_baudrate_config()
Return type:[bool, int]

Returns the baudrate config, see set_spitfp_baudrate_config().

New in version 2.3.4 (Firmware).

The returned array contains the elements enable_dynamic_baudrate and minimum_dynamic_baudrate.

BrickServo->get_send_timeout_count($communication_method)
Parameters:$communication_method -- int
Return type:int

Returns the timeout count for the different communication methods.

The methods 0-2 are available for all Bricks, 3-7 only for Master Bricks.

This function is mostly used for debugging during development, in normal operation the counters should nearly always stay at 0.

The following constants are available for this function:

  • BrickServo->COMMUNICATION_METHOD_NONE = 0
  • BrickServo->COMMUNICATION_METHOD_USB = 1
  • BrickServo->COMMUNICATION_METHOD_SPI_STACK = 2
  • BrickServo->COMMUNICATION_METHOD_CHIBI = 3
  • BrickServo->COMMUNICATION_METHOD_RS485 = 4
  • BrickServo->COMMUNICATION_METHOD_WIFI = 5
  • BrickServo->COMMUNICATION_METHOD_ETHERNET = 6
  • BrickServo->COMMUNICATION_METHOD_WIFI_V2 = 7

New in version 2.3.2 (Firmware).

BrickServo->set_spitfp_baudrate($bricklet_port, $baudrate)
Parameters:
  • $bricklet_port -- char
  • $baudrate -- int
Return type:

undef

Sets the baudrate for a specific Bricklet port ('a' - 'd'). The baudrate can be in the range 400000 to 2000000.

If you want to increase the throughput of Bricklets you can increase the baudrate. If you get a high error count because of high interference (see get_spitfp_error_count()) you can decrease the baudrate.

If the dynamic baudrate feature is enabled, the baudrate set by this function corresponds to the maximum baudrate (see set_spitfp_baudrate_config()).

Regulatory testing is done with the default baudrate. If CE compatibility or similar is necessary in you applications we recommend to not change the baudrate.

The default baudrate for all ports is 1400000.

New in version 2.3.2 (Firmware).

BrickServo->get_spitfp_baudrate($bricklet_port)
Parameters:$bricklet_port -- char
Return type:int

Returns the baudrate for a given Bricklet port, see set_spitfp_baudrate().

New in version 2.3.2 (Firmware).

BrickServo->get_spitfp_error_count($bricklet_port)
Parameters:$bricklet_port -- char
Return type:[int, int, int, int]

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Brick side. All Bricklets have a similar function that returns the errors on the Bricklet side.

New in version 2.3.2 (Firmware).

The returned array contains the elements error_count_ack_checksum, error_count_message_checksum, error_count_frame and error_count_overflow.

BrickServo->enable_status_led()
Return type:undef

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).

BrickServo->disable_status_led()
Return type:undef

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).

BrickServo->is_status_led_enabled()
Return type:bool

Returns true if the status LED is enabled, false otherwise.

New in version 2.3.1 (Firmware).

BrickServo->get_protocol1_bricklet_name($port)
Parameters:$port -- char
Return type:[int, [int, int, int], string]

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 array contains the elements protocol_version, firmware_version and name.

BrickServo->get_chip_temperature()
Return type:int

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.

BrickServo->reset()
Return type:undef

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!

BrickServo->get_identity()
Return type:[string, string, char, [int, int, int], [int, int, int], int]

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 array contains the elements uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions

BrickServo->register_callback($id, $callback)
Parameters:
  • $id -- int
  • $callback -- string
Return type:

undef

Registers the given $function name with the given $callback_id.

The available callback IDs with corresponding function signatures are listed below.

BrickServo->set_minimum_voltage($voltage)
Parameters:$voltage -- int
Return type:undef

Sets the minimum voltage in mV, below which the CALLBACK_UNDER_VOLTAGE callback is triggered. The minimum possible value that works with the Servo Brick is 5V. 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 5V (5000mV).

BrickServo->get_minimum_voltage()
Return type:int

Returns the minimum voltage as set by set_minimum_voltage()

BrickServo->enable_position_reached_callback()
Return type:undef

Enables the CALLBACK_POSITION_REACHED callback.

Default is disabled.

New in version 2.0.1 (Firmware).

BrickServo->disable_position_reached_callback()
Return type:undef

Disables the CALLBACK_POSITION_REACHED callback.

Default is disabled.

New in version 2.0.1 (Firmware).

BrickServo->is_position_reached_callback_enabled()
Return type:bool

Returns true if CALLBACK_POSITION_REACHED callback is enabled, false otherwise.

New in version 2.0.1 (Firmware).

BrickServo->enable_velocity_reached_callback()
Return type:undef

Enables the CALLBACK_VELOCITY_REACHED callback.

Default is disabled.

New in version 2.0.1 (Firmware).

BrickServo->disable_velocity_reached_callback()
Return type:undef

Disables the CALLBACK_VELOCITY_REACHED callback.

Default is disabled.

New in version 2.0.1 (Firmware).

BrickServo->is_velocity_reached_callback_enabled()
Return type:bool

Returns true if CALLBACK_VELOCITY_REACHED callback is enabled, false otherwise.

New in version 2.0.1 (Firmware).

Callbacks

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 name:

sub my_callback
{
    print "@_[0]";
}

$servo->register_callback(BrickServo->CALLBACK_EXAMPLE, 'my_callback')

The callback function will be called from an internal thread of the IP Connection. In contrast to many other programming languages, variables are not automatically shared between threads in Perl. If you want to share a global variable between a callback function and the rest for your program it has to be marked as :shared. See the documentation of the threads::shared Perl module for more details.

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.

BrickServo->CALLBACK_UNDER_VOLTAGE
Parameters:$voltage -- int

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.

BrickServo->CALLBACK_POSITION_REACHED
Parameters:
  • $servo_num -- int
  • $position -- int

This callback is triggered when a position set by set_position() is reached. If the new position matches the current position then the callback is not triggered, because the servo didn't move. The parameters are the servo and the position that is reached.

You can enable this callback with enable_position_reached_callback().

Note

Since we can't get any feedback from the servo, this only works if the velocity (see set_velocity()) is set smaller or equal to the maximum velocity of the servo. Otherwise the servo will lag behind the control value and the callback will be triggered too early.

BrickServo->CALLBACK_VELOCITY_REACHED
Parameters:
  • $servo_num -- int
  • $velocity -- int

This callback is triggered when a velocity set by set_velocity() is reached. The parameters are the servo and the velocity that is reached.

You can enable this callback with enable_velocity_reached_callback().

Note

Since we can't get any feedback from the servo, this only works if the acceleration (see set_acceleration()) is set smaller or equal to the maximum acceleration of the servo. Otherwise the servo will lag behind the control value and the callback will be triggered too early.

Constants

BrickServo->DEVICE_IDENTIFIER

This constant is used to identify a Servo 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.

BrickServo->DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Servo Brick.