Deutsch
English
Menu
Specifications / Modbus Protocol / API / Bricks (Discontinued) / DC Brick

Modbus - DC Brick

This is the description of the Modbus protocol for the DC Brick. General information and technical specifications for the DC Brick are summarized in its hardware description.

API

A general description of the Modbus protocol structure can be found here.

Basic Functions

BrickDC.set_velocity
Function ID:
  • 1
Request:
  • velocity – Type: int16, Unit: 100/32767 %, Range: [-215 + 1 to 215 - 1], Default: 0
Response:
  • no response

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.

BrickDC.get_velocity
Function ID:
  • 2
Request:
  • empty payload
Response:
  • velocity – Type: int16, Unit: 100/32767 %, Range: [-215 + 1 to 215 - 1], Default: 0

Returns the velocity as set by set_velocity.

BrickDC.get_current_velocity
Function ID:
  • 3
Request:
  • empty payload
Response:
  • velocity – Type: int16, Unit: 100/32767 %, Range: [-215 + 1 to 215 - 1], Default: 0

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
Function ID:
  • 4
Request:
  • acceleration – Type: uint16, Unit: 100/32767 %/s, Range: [0 to 216 - 1], Default: 10000
Response:
  • no response

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.

BrickDC.get_acceleration
Function ID:
  • 5
Request:
  • empty payload
Response:
  • acceleration – Type: uint16, Unit: 100/32767 %/s, Range: [0 to 216 - 1], Default: 10000

Returns the acceleration as set by set_acceleration.

BrickDC.full_brake
Function ID:
  • 8
Request:
  • empty payload
Response:
  • no response

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
Function ID:
  • 12
Request:
  • empty payload
Response:
  • no response

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

BrickDC.disable
Function ID:
  • 13
Request:
  • empty payload
Response:
  • no response

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

Warning

Disabling the driver chip while the motor is still turning can damage the driver chip. The motor should be stopped calling set_velocity with 0 before disabling the motor power. The set_velocity function will not wait until the motor is actually stopped. You have to explicitly wait for the appropriate time after calling the set_velocity function before calling the disable function.

BrickDC.is_enabled
Function ID:
  • 14
Request:
  • empty payload
Response:
  • enabled – Type: bool, Default: false

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

Advanced Functions

BrickDC.set_pwm_frequency
Function ID:
  • 6
Request:
  • frequency – Type: uint16, Unit: 1 Hz, Range: [1 to 20000], Default: 15000
Response:
  • no response

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.

BrickDC.get_pwm_frequency
Function ID:
  • 7
Request:
  • empty payload
Response:
  • frequency – Type: uint16, Unit: 1 Hz, Range: [1 to 20000], Default: 15000

Returns the PWM frequency as set by set_pwm_frequency.

BrickDC.get_stack_input_voltage
Function ID:
  • 9
Request:
  • empty payload
Response:
  • voltage – Type: uint16, Unit: 1 mV, Range: [0 to 216 - 1]

Returns the stack input voltage. 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
Function ID:
  • 10
Request:
  • empty payload
Response:
  • voltage – Type: uint16, Unit: 1 mV, Range: [0 to 216 - 1]

Returns the external input voltage. 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
Function ID:
  • 11
Request:
  • empty payload
Response:
  • voltage – Type: uint16, Unit: 1 mA, Range: [0 to 216 - 1]

Returns the current consumption of the motor.

BrickDC.set_drive_mode
Function ID:
  • 17
Request:
  • mode – Type: uint8, Range: See meanings, Default: 0
Response:
  • no response

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 following meanings are defined for the elements of this function:

For mode:

  • 0 = Drive Brake
  • 1 = Drive Coast
BrickDC.get_drive_mode
Function ID:
  • 18
Request:
  • empty payload
Response:
  • mode – Type: uint8, Range: See meanings, Default: 0

Returns the drive mode, as set by set_drive_mode.

The following meanings are defined for the elements of this function:

For mode:

  • 0 = Drive Brake
  • 1 = Drive Coast
BrickDC.set_spitfp_baudrate_config
Function ID:
  • 231
Request:
  • enable_dynamic_baudrate – Type: bool, Default: true
  • minimum_dynamic_baudrate – Type: uint32, Unit: 1 Bd, Range: [400000 to 2000000], Default: 400000
Response:
  • no response

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 sent/received and decreased linearly if little data is sent/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.

New in version 2.3.5 (Firmware).

BrickDC.get_spitfp_baudrate_config
Function ID:
  • 232
Request:
  • empty payload
Response:
  • enable_dynamic_baudrate – Type: bool, Default: true
  • minimum_dynamic_baudrate – Type: uint32, Unit: 1 Bd, Range: [400000 to 2000000], Default: 400000

Returns the baudrate config, see set_spitfp_baudrate_config.

New in version 2.3.5 (Firmware).

BrickDC.get_send_timeout_count
Function ID:
  • 233
Request:
  • communication_method – Type: uint8, Range: See meanings
Response:
  • timeout_count – Type: uint32, Range: [0 to 232 - 1]

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.

New in version 2.3.3 (Firmware).

The following meanings are defined for the elements of this function:

For communication_method:

  • 0 = None
  • 1 = USB
  • 2 = SPI Stack
  • 3 = Chibi
  • 4 = RS485
  • 5 = WIFI
  • 6 = Ethernet
  • 7 = WIFI V2
BrickDC.set_spitfp_baudrate
Function ID:
  • 234
Request:
  • bricklet_port – Type: char, Range: ['a' to 'b']
  • baudrate – Type: uint32, Unit: 1 Bd, Range: [400000 to 2000000], Default: 1400000
Response:
  • no response

Sets the baudrate for a specific Bricklet port.

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 your applications we recommend to not change the baudrate.

New in version 2.3.3 (Firmware).

BrickDC.get_spitfp_baudrate
Function ID:
  • 235
Request:
  • bricklet_port – Type: char, Range: ['a' to 'b']
Response:
  • baudrate – Type: uint32, Unit: 1 Bd, Range: [400000 to 2000000], Default: 1400000

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

New in version 2.3.3 (Firmware).

BrickDC.get_spitfp_error_count
Function ID:
  • 237
Request:
  • bricklet_port – Type: char, Range: ['a' to 'b']
Response:
  • error_count_ack_checksum – Type: uint32, Range: [0 to 232 - 1]
  • error_count_message_checksum – Type: uint32, Range: [0 to 232 - 1]
  • error_count_frame – Type: uint32, Range: [0 to 232 - 1]
  • error_count_overflow – Type: uint32, Range: [0 to 232 - 1]

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).

BrickDC.enable_status_led
Function ID:
  • 238
Request:
  • empty payload
Response:
  • no response

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
Function ID:
  • 239
Request:
  • empty payload
Response:
  • no response

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
Function ID:
  • 240
Request:
  • empty payload
Response:
  • enabled – Type: bool, Default: true

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

New in version 2.3.1 (Firmware).

BrickDC.get_chip_temperature
Function ID:
  • 242
Request:
  • empty payload
Response:
  • temperature – Type: int16, Unit: 1/10 °C, Range: [-215 to 215 - 1]

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 an accuracy of ±15%. Practically it is only useful as an indicator for temperature changes.

BrickDC.reset
Function ID:
  • 243
Request:
  • empty payload
Response:
  • no response

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
Function ID:
  • 255
Request:
  • empty payload
Response:
  • uid – Type: char[8]
  • connected_uid – Type: char[8]
  • position – Type: char, Range: ['0' to '8']
  • hardware_version – Type: uint8[3]
    • 0: major – Type: uint8, Range: [0 to 255]
    • 1: minor – Type: uint8, Range: [0 to 255]
    • 2: revision – Type: uint8, Range: [0 to 255]
  • firmware_version – Type: uint8[3]
    • 0: major – Type: uint8, Range: [0 to 255]
    • 1: minor – Type: uint8, Range: [0 to 255]
    • 2: revision – Type: uint8, Range: [0 to 255]
  • device_identifier – Type: uint16, Range: [0 to 216 - 1]

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 is the position in the stack from '0' (bottom) to '8' (top).

The device identifier numbers can be found here. 

Callback Configuration Functions

BrickDC.set_minimum_voltage
Function ID:
  • 15
Request:
  • voltage – Type: uint16, Unit: 1 mV, Range: [0 to 216 - 1], Default: 6000
Response:
  • no response

Sets the minimum voltage, 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.

BrickDC.get_minimum_voltage
Function ID:
  • 16
Request:
  • empty payload
Response:
  • voltage – Type: uint16, Unit: 1 mV, Range: [0 to 216 - 1], Default: 6000

Returns the minimum voltage as set by set_minimum_voltage

BrickDC.set_current_velocity_period
Function ID:
  • 19
Request:
  • period – Type: uint16, Unit: 1 ms, Range: [0 to 216 - 1], Default: 0
Response:
  • no response

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

BrickDC.get_current_velocity_period
Function ID:
  • 20
Request:
  • empty payload
Response:
  • period – Type: uint16, Unit: 1 ms, Range: [0 to 216 - 1], Default: 0

Returns the period as set by set_current_velocity_period.

Callbacks

BrickDC.CALLBACK_UNDER_VOLTAGE
Function ID:
  • 21
Response:
  • voltage – Type: uint16, Unit: 1 mV, Range: [0 to 216 - 1]

This callback is triggered when the input voltage drops below the value set by set_minimum_voltage. The response value is the current voltage.

BrickDC.CALLBACK_EMERGENCY_SHUTDOWN
Function ID:
  • 22
Response:
  • empty payload

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
Function ID:
  • 23
Response:
  • velocity – Type: int16, Unit: 100/32767 %, Range: [-215 + 1 to 215 - 1]

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
Function ID:
  • 24
Response:
  • velocity – Type: int16, Unit: 100/32767 %, Range: [-215 + 1 to 215 - 1]

This callback is triggered with the period that is set by set_current_velocity_period. The response value 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.

Internal Functions

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.

BrickDC.get_protocol1_bricklet_name
Function ID:
  • 241
Request:
  • port – Type: char, Range: ['a' to 'b']
Response:
  • protocol_version – Type: uint8, Range: [0 to 255]
  • firmware_version – Type: uint8[3]
    • 0: major – Type: uint8, Range: [0 to 255]
    • 1: minor – Type: uint8, Range: [0 to 255]
    • 2: revision – Type: uint8, Range: [0 to 255]
  • name – Type: char[40]

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.

BrickDC.write_bricklet_plugin
Function ID:
  • 246
Request:
  • port – Type: char, Range: ['a' to 'b']
  • offset – Type: uint8, Range: [0 to 255]
  • chunk – Type: uint8[32], Range: [0 to 255]
Response:
  • no response

Writes 32 bytes of firmware to the bricklet attached at the given port. The bytes are written to the position offset * 32.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickDC.read_bricklet_plugin
Function ID:
  • 247
Request:
  • port – Type: char, Range: ['a' to 'b']
  • offset – Type: uint8, Range: [0 to 255]
Response:
  • chunk – Type: uint8[32], Range: [0 to 255]

Reads 32 bytes of firmware from the bricklet attached at the given port. The bytes are read starting at the position offset * 32.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.