Shell - DC Brick – Tinkerforge

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# 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 it

    # change to your UID
    uid=XYZ

    # use PWM frequency of 10kHz
    tinkerforge call dc-brick $uid set-pwm-frequency 10000

    # use drive/coast instead of drive/brake
    tinkerforge call dc-brick $uid set-drive-mode drive-coast

    # enable motor controller
    tinkerforge call dc-brick $uid enable

    # slow acceleration
    tinkerforge call dc-brick $uid set-acceleration 5000

    # full speed forward
    tinkerforge call dc-brick $uid set-velocity 32767

### Callback

Download (example-callback.sh)

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

    # change to your UID
    uid=XYZ

    # enable motor controller
    tinkerforge call dc-brick $uid enable

    # the acceleration has to be smaller or equal to the maximum acceleration
    # of the DC motor, otherwise the velocity-reached will be triggered too early

    # slow acceleration
    tinkerforge call dc-brick $uid set-acceleration 5000

    # full speed forward
    tinkerforge call dc-brick $uid set-velocity 32767

    # this will be triggerd every time a velocity set with set-velocity is reached
    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"

## 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-brake` = 0, for <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-brake` = 0, for mode
  - `drive-coast` = 1, for mode

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, `velocity-reached` 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.

  `current-velocity` is only triggered after the set period if there is a change in the velocity.

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