Perl - DC Brick

This is the description of the Perl API bindings for the DC Brick. General information and technical specifications for the DC 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::BrickDC;

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

my $ipcon = Tinkerforge::IPConnection->new(); # Create IP connection
my $dc = Tinkerforge::BrickDC->new(&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 10kHz
$dc->set_acceleration(5000); # Slow acceleration
$dc->set_velocity(32767); # Full speed forward
$dc->enable(); # Enable motor power

print "Press key to exit\n";
<STDIN>;
$dc->disable(); # Disable motor power
$ipcon->disconnect();

Callback

Download (example_callback.pl)

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#!/usr/bin/perl

use strict;
use Tinkerforge::IPConnection;
use Tinkerforge::BrickDC;

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

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

# Use velocity reached callback to swing back and forth
# between full speed forward and full speed backward
sub cb_velocity_reached
{
    my ($velocity) = @_;

    if ($velocity == 32767)
    {
        print "Velocity: Full speed forward, now turning backward\n";
        $dc->set_velocity(-32767);
    }   
    elsif ($velocity == -32767)
    {
        print "Velocity: Full speed backward, now turning forward\n";
        $dc->set_velocity(32767);
    }    
    else
    {
        print "Error\n"; # Can only happen if another program sets velocity
    }
}

$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_acceleration(5000); # Slow acceleration
$dc->set_velocity(32767); # Full speed forward

# Register velocity reached callback to subroutine cb_velocity_reached
$dc->register_callback($dc->CALLBACK_VELOCITY_REACHED, 'cb_velocity_reached');

# Enable motor power
$dc->enable();

print "Press key to exit\n";
<STDIN>;
$dc->disable(); # Disable motor power
$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.

Basic Functions

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

BrickDC

Creates an object with the unique device ID $uid:

$dc = BrickDC->new("YOUR_DEVICE_UID", $ipcon);

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

BrickDC->set_velocity($velocity)
Parameters:$velocity -- int
Return type:undef

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_acceleration()), 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().

The default velocity is 0.

BrickDC->get_velocity()
Return type:int

Returns the velocity as set by set_velocity().

BrickDC->get_current_velocity()
Return type:int

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().

BrickDC->set_acceleration($acceleration)
Parameters:$acceleration -- int
Return type:undef

Sets the acceleration 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 is set to 0, there is no speed ramping, i.e. a new velocity is immediately given to the motor.

The default acceleration is 10000.

BrickDC->get_acceleration()
Return type:int

Returns the acceleration as set by set_acceleration().

BrickDC->full_brake()
Return type:undef

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.

BrickDC->enable()
Return type:undef

Enables the driver chip. The driver parameters can be configured (velocity, acceleration, etc) before it is enabled.

BrickDC->disable()
Return type:undef

Disables the driver chip. The configurations are kept (velocity, acceleration, etc) but the motor is not driven until it is enabled again.

BrickDC->is_enabled()
Return type:bool

Returns true if the driver chip is enabled, false otherwise.

Advanced Functions

BrickDC->set_pwm_frequency($frequency)
Parameters:$frequency -- int
Return type:undef

Sets the frequency (in Hz) of the PWM with which the motor is driven. The possible range of the frequency is 1-20000Hz. 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.

The default frequency is 15 kHz.

BrickDC->get_pwm_frequency()
Return type:int

Returns the PWM frequency (in Hz) as set by set_pwm_frequency().

BrickDC->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.

BrickDC->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 DC 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.

BrickDC->get_current_consumption()
Return type:int

Returns the current consumption of the motor in mA.

BrickDC->set_drive_mode($mode)
Parameters:$mode -- int
Return type:undef

Sets the drive mode. Possible modes are:

  • 0 = Drive/Brake
  • 1 = Drive/Coast

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 default value is 0 = Drive/Brake.

The following constants are available for this function:

  • BrickDC->DRIVE_MODE_DRIVE_BRAKE = 0
  • BrickDC->DRIVE_MODE_DRIVE_COAST = 1
BrickDC->get_drive_mode()
Return type:int

Returns the drive mode, as set by set_drive_mode().

The following constants are available for this function:

  • BrickDC->DRIVE_MODE_DRIVE_BRAKE = 0
  • BrickDC->DRIVE_MODE_DRIVE_COAST = 1
BrickDC->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.

BrickDC->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.

BrickDC->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:

  • BrickDC->FUNCTION_SET_VELOCITY = 1
  • BrickDC->FUNCTION_SET_ACCELERATION = 4
  • BrickDC->FUNCTION_SET_PWM_FREQUENCY = 6
  • BrickDC->FUNCTION_FULL_BRAKE = 8
  • BrickDC->FUNCTION_ENABLE = 12
  • BrickDC->FUNCTION_DISABLE = 13
  • BrickDC->FUNCTION_SET_MINIMUM_VOLTAGE = 15
  • BrickDC->FUNCTION_SET_DRIVE_MODE = 17
  • BrickDC->FUNCTION_SET_CURRENT_VELOCITY_PERIOD = 19
  • BrickDC->FUNCTION_SET_SPITFP_BAUDRATE_CONFIG = 231
  • BrickDC->FUNCTION_SET_SPITFP_BAUDRATE = 234
  • BrickDC->FUNCTION_ENABLE_STATUS_LED = 238
  • BrickDC->FUNCTION_DISABLE_STATUS_LED = 239
  • BrickDC->FUNCTION_RESET = 243
BrickDC->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.

BrickDC->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 2.3.5 (Firmware).

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

Returns the baudrate config, see set_spitfp_baudrate_config().

New in version 2.3.5 (Firmware).

The returned array contains the elements enable_dynamic_baudrate and minimum_dynamic_baudrate.

BrickDC->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:

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

New in version 2.3.3 (Firmware).

BrickDC->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 2.3.3 (Firmware).

BrickDC->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 2.3.3 (Firmware).

BrickDC->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 2.3.3 (Firmware).

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

BrickDC->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).

BrickDC->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).

BrickDC->is_status_led_enabled()
Return type:bool

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

New in version 2.3.1 (Firmware).

BrickDC->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.

BrickDC->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.

BrickDC->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!

BrickDC->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

BrickDC->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.

BrickDC->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 DC Brick is 6V. You can use this function to detect the discharge of a battery that is used to drive the motor. If you have a fixed power supply, you likely do not need this functionality.

The default value is 6V.

BrickDC->get_minimum_voltage()
Return type:int

Returns the minimum voltage as set by set_minimum_voltage()

BrickDC->set_current_velocity_period($period)
Parameters:$period -- int
Return type:undef

Sets a period in ms with which the CALLBACK_CURRENT_VELOCITY callback is triggered. A period of 0 turns the callback off.

The default value is 0.

BrickDC->get_current_velocity_period()
Return type:int

Returns the period as set by set_current_velocity_period().

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]";
}

$dc->register_callback(BrickDC->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.

BrickDC->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.

BrickDC->CALLBACK_EMERGENCY_SHUTDOWN

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, enable() 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.

BrickDC->CALLBACK_VELOCITY_REACHED
Parameters:$velocity -- int

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_acceleration()) 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.

BrickDC->CALLBACK_CURRENT_VELOCITY
Parameters:$velocity -- int

This callback is triggered with the period that is set by set_current_velocity_period(). 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.

Constants

BrickDC->DEVICE_IDENTIFIER

This constant is used to identify a DC 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.

BrickDC->DEVICE_DISPLAY_NAME

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