Ruby - DC Brick

This is the description of the Ruby 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 Ruby API bindings is part of their general description.

Examples

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

Configuration

Download (example_configuration.rb)

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#!/usr/bin/env ruby
# -*- ruby encoding: utf-8 -*-

require 'tinkerforge/ip_connection'
require 'tinkerforge/brick_dc'

include Tinkerforge

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

ipcon = IPConnection.new # Create IP connection
dc = 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 BrickDC::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

puts 'Press key to exit'
$stdin.gets
dc.disable # Disable motor power
ipcon.disconnect

Callback

Download (example_callback.rb)

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#!/usr/bin/env ruby
# -*- ruby encoding: utf-8 -*-

require 'tinkerforge/ip_connection'
require 'tinkerforge/brick_dc'

include Tinkerforge

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

ipcon = IPConnection.new # Create IP connection
dc = BrickDC.new 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_acceleration 5000 # Slow acceleration
dc.set_velocity 32767 # Full speed forward

# Use velocity reached callback to swing back and forth
# between full speed forward and full speed backward
dc.register_callback(BrickDC::CALLBACK_VELOCITY_REACHED) do |velocity|
  if velocity == 32767
    puts 'Velocity: Full speed forward, now turning backward'
    dc.set_velocity(-32767)
  elsif velocity == -32767
    puts 'Velocity: Full speed backward, now turning forward'
    dc.set_velocity 32767
  else
    puts 'Error' # Can only happen if another program sets velocity
  end
end

# Enable motor power
dc.enable

puts 'Press key to exit'
$stdin.gets
dc.disable # Disable motor power
ipcon.disconnect

API

All methods listed below are thread-safe.

Basic Functions

BrickDC::new(uid, ipcon) → dc
Parameters:
  • uid -- str
  • ipcon -- IPConnection

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) → nil
Parameters:velocity -- int

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 → int

Returns the velocity as set by #set_velocity.

BrickDC#get_current_velocity → 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) → nil
Parameters:acceleration -- int

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 → int

Returns the acceleration as set by #set_acceleration.

BrickDC#full_brake → nil

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 → nil

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

BrickDC#disable → nil

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 → bool

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

Advanced Functions

BrickDC#set_pwm_frequency(frequency) → nil
Parameters:frequency -- int

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 → int

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

BrickDC#get_stack_input_voltage → 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 → 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 → int

Returns the current consumption of the motor in mA.

BrickDC#set_drive_mode(mode) → nil
Parameters:mode -- int

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 → 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 → [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) → bool
Parameters:function_id -- int

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) → nil
Parameters:
  • function_id -- int
  • response_expected -- bool

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) → nil
Parameters:response_expected -- bool

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) → nil
Parameters:
  • enable_dynamic_baudrate -- bool
  • minimum_dynamic_baudrate -- int

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 → [bool, int]

Returns the baudrate config, see #set_spitfp_baudrate_config.

New in version 2.3.5 (Firmware).

The returned array has the values enable_dynamic_baudrate and minimum_dynamic_baudrate.

BrickDC#get_send_timeout_count(communication_method) → int
Parameters:communication_method -- 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) → nil
Parameters:
  • bricklet_port -- str
  • baudrate -- int

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) → int
Parameters:bricklet_port -- str

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) → [int, int, int, int]
Parameters:bricklet_port -- str

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 has the values error_count_ack_checksum, error_count_message_checksum, error_count_frame and error_count_overflow.

BrickDC#enable_status_led → nil

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 → nil

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 → bool

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

New in version 2.3.1 (Firmware).

BrickDC#get_protocol1_bricklet_name(port) → [int, [int, int, int], str]
Parameters:port -- 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 array has the values protocol_version, firmware_version and name.

BrickDC#get_chip_temperature → 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 → nil

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 → [str, str, str, [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 has the values uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions

BrickDC#register_callback(callback_id) { |param [, ...]| block } → nil
Parameters:callback_id -- int

Registers the given block with the given callback_id.

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

BrickDC#set_minimum_voltage(voltage) → nil
Parameters:voltage -- int

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 → int

Returns the minimum voltage as set by #set_minimum_voltage

BrickDC#set_current_velocity_period(period) → nil
Parameters:period -- int

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 → 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 is a block:

dc.register_callback BrickDC::CALLBACK_EXAMPLE, do |param|
  puts "#{param}"
end

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.