Shell - DC Brick

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

Examples

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

Configuration

Download (example-configuration.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XXYYZZ # Change XXYYZZ to the UID of your DC Brick

tinkerforge call dc-brick $uid set-drive-mode drive-mode-drive-coast
tinkerforge call dc-brick $uid set-pwm-frequency 10000 # Use PWM frequency of 10kHz
tinkerforge call dc-brick $uid set-acceleration 5000 # Slow acceleration
tinkerforge call dc-brick $uid set-velocity 32767 # Full speed forward
tinkerforge call dc-brick $uid enable # Enable motor power

echo "Press key to exit"; read dummy

tinkerforge call dc-brick $uid disable # Disable motor power

Callback

Download (example-callback.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XXYYZZ # Change XXYYZZ to the UID of your DC Brick

# 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
tinkerforge call dc-brick $uid set-acceleration 5000 # Slow acceleration
tinkerforge call dc-brick $uid set-velocity 32767 # Full speed forward

# Use velocity reached callback to swing back and forth
# between full speed forward and full speed backward
tinkerforge dispatch dc-brick $uid velocity-reached\
 --execute "if   [ {velocity} -eq  32767 ]; then tinkerforge call dc-brick $uid set-velocity -32767;
            elif [ {velocity} -eq -32767 ]; then tinkerforge call dc-brick $uid set-velocity  32767;
            else echo error; fi" &

# Enable motor power
tinkerforge call dc-brick $uid enable

echo "Press key to exit"; read dummy

tinkerforge call dc-brick $uid disable # Disable motor power

kill -- -$$ # Stop callback dispatch in background

API

Possible exit codes for all tinkerforge commands are:

  • 1: interrupted (ctrl+c)
  • 2: syntax error
  • 21: Python 2.5 or newer is required
  • 22: Python argparse module is missing
  • 23: socket error
  • 24: other exception
  • 25: invalid placeholder in format string
  • 26: authentication error
  • 201: timeout occurred
  • 209: invalid argument value
  • 210: function is not supported
  • 211: unknown error

Command Structure

The common options of the call and dispatch commands are documented here. The specific command structure is shown below.

tinkerforge call dc-brick [<option>..] <uid> <function> [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The call command is used to call a function of the DC Brick. It can take several options:

  • --help shows help for the specific call command and exits
  • --list-functions shows a list of known functions of the DC Brick and exits
tinkerforge dispatch dc-brick [<option>..] <uid> <callback>
Parameters:
  • <uid> -- string
  • <callback> -- string

The dispatch command is used to dispatch a callback of the DC Brick. It can take several options:

  • --help shows help for the specific dispatch command and exits
  • --list-callbacks shows a list of known callbacks of the DC Brick and exits
tinkerforge call dc-brick <uid> <function> [<option>..] [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The <function> to be called can take different options depending of its kind. All functions can take the following options:

  • --help shows help for the specific function and exits

Getter functions can take the following options:

  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Setter functions can take the following options:

  • --expect-response requests response and waits for it

The --expect-response option for setter functions allows to detect timeouts and other error conditions calls of setters as well. The device will then send a response for this purpose. If this option is not given for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

tinkerforge dispatch dc-brick <uid> <callback> [<option>..]
Parameters:
  • <uid> -- string
  • <callback> -- string

The <callback> to be dispatched can take several options:

  • --help shows help for the specific callback and exits
  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Basic Functions

tinkerforge call dc-brick <uid> set-velocity <velocity>
Parameters:
  • <velocity> -- int
Output:

no output

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.

tinkerforge call dc-brick <uid> get-velocity
Output:
  • velocity -- int

Returns the velocity as set by set-velocity.

tinkerforge call dc-brick <uid> get-current-velocity
Output:
  • 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.

tinkerforge call dc-brick <uid> set-acceleration <acceleration>
Parameters:
  • <acceleration> -- int
Output:

no output

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.

tinkerforge call dc-brick <uid> get-acceleration
Output:
  • acceleration -- int

Returns the acceleration as set by set-acceleration.

tinkerforge call dc-brick <uid> full-brake
Output:no output

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.

tinkerforge call dc-brick <uid> enable
Output:no output

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

tinkerforge call dc-brick <uid> disable
Output:no output

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

tinkerforge call dc-brick <uid> is-enabled
Output:
  • enabled -- bool

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

Advanced Functions

tinkerforge call dc-brick <uid> set-pwm-frequency <frequency>
Parameters:
  • <frequency> -- int
Output:

no output

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.

tinkerforge call dc-brick <uid> get-pwm-frequency
Output:
  • frequency -- int

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

tinkerforge call dc-brick <uid> get-stack-input-voltage
Output:
  • 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.

tinkerforge call dc-brick <uid> get-external-input-voltage
Output:
  • 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.

tinkerforge call dc-brick <uid> get-current-consumption
Output:
  • voltage -- int

Returns the current consumption of the motor in mA.

tinkerforge call dc-brick <uid> set-drive-mode <mode>
Parameters:
  • <mode> -- int (has symbols)
Output:

no output

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 symbols are available for this function:

  • drive-mode-drive-brake = 0, for <mode>
  • drive-mode-drive-coast = 1, for <mode>
tinkerforge call dc-brick <uid> get-drive-mode
Output:
  • mode -- int (has symbols)

Returns the drive mode, as set by set-drive-mode.

The following symbols are available for this function:

  • drive-mode-drive-brake = 0, for mode
  • drive-mode-drive-coast = 1, for mode
tinkerforge call dc-brick <uid> set-spitfp-baudrate-config <enable-dynamic-baudrate> <minimum-dynamic-baudrate>
Parameters:
  • <enable-dynamic-baudrate> -- bool
  • <minimum-dynamic-baudrate> -- int
Output:

no output

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).

tinkerforge call dc-brick <uid> get-spitfp-baudrate-config
Output:
  • enable-dynamic-baudrate -- bool
  • minimum-dynamic-baudrate -- int

Returns the baudrate config, see set-spitfp-baudrate-config.

New in version 2.3.5 (Firmware).

tinkerforge call dc-brick <uid> get-send-timeout-count <communication-method>
Parameters:
  • <communication-method> -- int (has symbols)
Output:
  • timeout-count -- 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 symbols are available for this function:

  • communication-method-none = 0, for <communication-method>
  • communication-method-usb = 1, for <communication-method>
  • communication-method-spi-stack = 2, for <communication-method>
  • communication-method-chibi = 3, for <communication-method>
  • communication-method-rs485 = 4, for <communication-method>
  • communication-method-wifi = 5, for <communication-method>
  • communication-method-ethernet = 6, for <communication-method>
  • communication-method-wifi-v2 = 7, for <communication-method>

New in version 2.3.3 (Firmware).

tinkerforge call dc-brick <uid> set-spitfp-baudrate <bricklet-port> <baudrate>
Parameters:
  • <bricklet-port> -- char
  • <baudrate> -- int
Output:

no output

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).

tinkerforge call dc-brick <uid> get-spitfp-baudrate <bricklet-port>
Parameters:
  • <bricklet-port> -- char
Output:
  • baudrate -- int

Returns the baudrate for a given Bricklet port, see set-spitfp-baudrate.

New in version 2.3.3 (Firmware).

tinkerforge call dc-brick <uid> get-spitfp-error-count <bricklet-port>
Parameters:
  • <bricklet-port> -- char
Output:
  • error-count-ack-checksum -- int
  • error-count-message-checksum -- int
  • error-count-frame -- int
  • error-count-overflow -- 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).

tinkerforge call dc-brick <uid> enable-status-led
Output:no output

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).

tinkerforge call dc-brick <uid> disable-status-led
Output:no output

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).

tinkerforge call dc-brick <uid> is-status-led-enabled
Output:
  • enabled -- bool

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

New in version 2.3.1 (Firmware).

tinkerforge call dc-brick <uid> get-protocol1-bricklet-name <port>
Parameters:
  • <port> -- char
Output:
  • protocol-version -- int
  • firmware-version -- int,int,int
  • name -- 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.

tinkerforge call dc-brick <uid> get-chip-temperature
Output:
  • 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.

tinkerforge call dc-brick <uid> reset
Output:no output

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!

tinkerforge call dc-brick <uid> get-identity
Output:
  • uid -- string
  • connected-uid -- string
  • position -- char
  • hardware-version -- int,int,int
  • firmware-version -- int,int,int
  • device-identifier -- int (has symbols)

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

Callback Configuration Functions

tinkerforge call dc-brick <uid> set-minimum-voltage <voltage>
Parameters:
  • <voltage> -- int
Output:

no output

Sets the minimum voltage in mV, below which the 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.

tinkerforge call dc-brick <uid> get-minimum-voltage
Output:
  • voltage -- int

Returns the minimum voltage as set by set-minimum-voltage

tinkerforge call dc-brick <uid> set-current-velocity-period <period>
Parameters:
  • <period> -- int
Output:

no output

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

The default value is 0.

tinkerforge call dc-brick <uid> get-current-velocity-period
Output:
  • period -- int

Returns the period as set by set-current-velocity-period.

Callbacks

Callbacks can be used to receive time critical or recurring data from the device:

tinkerforge dispatch dc-brick <uid> example

The available callbacks 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.

tinkerforge dispatch dc-brick <uid> under-voltage
Output:
  • 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.

tinkerforge dispatch dc-brick <uid> emergency-shutdown
Output:no output

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.

tinkerforge dispatch dc-brick <uid> velocity-reached
Output:
  • 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 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.

tinkerforge dispatch dc-brick <uid> current-velocity
Output:
  • 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 current-velocity callback is only triggered after the set period if there is a change in the velocity.