Go - DC Brick

This is the description of the Go 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 Go API bindings is part of their general description. Additional documentation can be found on godoc.org.

Examples

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

Configuration

Download (example_configuration.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/dc_brick"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"
const UID string = "XXYYZZ" // Change XXYYZZ to the UID of your DC Brick.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    dc, _ := dc_brick.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    dc.SetDriveMode(dc_brick.DriveModeDriveCoast)
    dc.SetPWMFrequency(10000) // Use PWM frequency of 10kHz
    dc.SetAcceleration(5000)  // Slow acceleration
    dc.SetVelocity(32767)     // Full speed forward
    dc.Enable()               // Enable motor power

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
    dc.Disable() // Disable motor power
}

Callback

Download (example_callback.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/dc_brick"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"
const UID string = "XXYYZZ" // Change XXYYZZ to the UID of your DC Brick.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    dc, _ := dc_brick.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // 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.SetAcceleration(5000) // Slow acceleration
    dc.SetVelocity(32767)    // Full speed forward

    dc.RegisterVelocityReachedCallback(func(velocity int16) {
        if velocity == 32767 {
            fmt.Println("Velocity: Full speed forward, now turning backward")
            dc.SetVelocity(-32767)
        } else if velocity == -32767 {
            fmt.Println("Velocity: Full speed backward, now turning forward")
            dc.SetVelocity(32767)
        } else {
            //can only happen if another program sets velocity
            fmt.Println("Error")
        }
    })

    // Enable motor power
    dc.Enable()

    fmt.Print("Press enter to exit.")
    fmt.Scanln()

    dc.Disable() // Disable motor power
}

API

The DC Brick API is defined in the package github.com/Tinkerforge/go-api-bindings/dc_brick

Nearly every function of the Go bindings can return an BrickletError, implementing the error interface. The error can have one of the following values:

  • BrickletErrorSuccess = 0
  • BrickletErrorInvalidParameter = 1
  • BrickletErrorFunctionNotSupported = 2
  • BrickletErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions

func NewDCBrick(uid string, ipcon *IPConnection)(device DCBrick, err error)

Creates a new DCBrick object with the unique device ID uid and adds it to the IPConnection ipcon:

This device object can be used after the IPConnection has been connected (see examples above).

func (*DCBrick)SetVelocity(velocity int16)(err error)

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 (*DCBrick) SetAcceleration), 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 (*DCBrick) SetPWMFrequency.

The default velocity is 0.

func (*DCBrick)GetVelocity()(velocity int16, err error)

Returns the velocity as set by (*DCBrick) SetVelocity.

func (*DCBrick)GetCurrentVelocity()(velocity int16, err error)

Returns the current velocity of the motor. This value is different from (*DCBrick) GetVelocity whenever the motor is currently accelerating to a goal set by (*DCBrick) SetVelocity.

func (*DCBrick)SetAcceleration(acceleration uint16)(err error)

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.

func (*DCBrick)GetAcceleration()(acceleration uint16, err error)

Returns the acceleration as set by (*DCBrick) SetAcceleration.

func (*DCBrick)FullBrake()(err error)

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 (*DCBrick) SetVelocity with 0 if you just want to stop the motor.

func (*DCBrick)Enable()(err error)

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

func (*DCBrick)Disable()(err error)

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

func (*DCBrick)IsEnabled()(enabled bool, err error)

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

Advanced Functions

func (*DCBrick)SetPWMFrequency(frequency uint16)(err error)

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.

func (*DCBrick)GetPWMFrequency()(frequency uint16, err error)

Returns the PWM frequency (in Hz) as set by (*DCBrick) SetPWMFrequency.

func (*DCBrick)GetStackInputVoltage()(voltage uint16, err error)

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.

func (*DCBrick)GetExternalInputVoltage()(voltage uint16, err error)

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.

func (*DCBrick)GetCurrentConsumption()(voltage uint16, err error)

Returns the current consumption of the motor in mA.

func (*DCBrick)SetDriveMode(mode DriveMode)(err error)

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:

  • DriveModeDriveBrake = 0
  • DriveModeDriveCoast = 1
func (*DCBrick)GetDriveMode()(mode DriveMode, err error)

Returns the drive mode, as set by (*DCBrick) SetDriveMode.

The following constants are available for this function:

  • DriveModeDriveBrake = 0
  • DriveModeDriveCoast = 1
func (*DCBrick)GetAPIVersion()(apiVersion [3]uint8, err error)

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.

func (*DCBrick)GetResponseExpected(functionId uint8)(responseExpected bool, err error)

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 (*DCBrick) SetResponseExpected. 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 (*DCBrick) SetResponseExpected for the list of function ID constants available for this function.

func (*DCBrick)SetResponseExpected(functionId uint8, responseExpected bool)(err error)

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:

  • FunctionSetVelocity = 1
  • FunctionSetAcceleration = 4
  • FunctionSetPWMFrequency = 6
  • FunctionFullBrake = 8
  • FunctionEnable = 12
  • FunctionDisable = 13
  • FunctionSetMinimumVoltage = 15
  • FunctionSetDriveMode = 17
  • FunctionSetCurrentVelocityPeriod = 19
  • FunctionSetSPITFPBaudrateConfig = 231
  • FunctionSetSPITFPBaudrate = 234
  • FunctionEnableStatusLED = 238
  • FunctionDisableStatusLED = 239
  • FunctionReset = 243
func (*DCBrick)SetResponseExpectedAll(responseExpected bool)(err error)

Changes the response expected flag for all setter and callback configuration functions of this device at once.

func (*DCBrick)SetSPITFPBaudrateConfig(enableDynamicBaudrate bool, minimumDynamicBaudrate uint32)(err error)

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 (*DCBrick) SetSPITFPBaudrate. If the dynamic baudrate is disabled, the baudrate as set by (*DCBrick) SetSPITFPBaudrate 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).

func (*DCBrick)GetSPITFPBaudrateConfig()(enableDynamicBaudrate bool, minimumDynamicBaudrate uint32, err error)

Returns the baudrate config, see (*DCBrick) SetSPITFPBaudrateConfig.

New in version 2.3.5 (Firmware).

func (*DCBrick)GetSendTimeoutCount(communicationMethod CommunicationMethod)(timeoutCount uint32, err error)

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:

  • CommunicationMethodNone = 0
  • CommunicationMethodUSB = 1
  • CommunicationMethodSPIStack = 2
  • CommunicationMethodChibi = 3
  • CommunicationMethodRS485 = 4
  • CommunicationMethodWIFI = 5
  • CommunicationMethodEthernet = 6
  • CommunicationMethodWIFIV2 = 7

New in version 2.3.3 (Firmware).

func (*DCBrick)SetSPITFPBaudrate(brickletPort rune, baudrate uint32)(err error)

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 (*DCBrick) GetSPITFPErrorCount) you can decrease the baudrate.

If the dynamic baudrate feature is enabled, the baudrate set by this function corresponds to the maximum baudrate (see (*DCBrick) SetSPITFPBaudrateConfig).

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).

func (*DCBrick)GetSPITFPBaudrate(brickletPort rune)(baudrate uint32, err error)

Returns the baudrate for a given Bricklet port, see (*DCBrick) SetSPITFPBaudrate.

New in version 2.3.3 (Firmware).

func (*DCBrick)GetSPITFPErrorCount(brickletPort rune)(errorCountACKChecksum uint32, errorCountMessageChecksum uint32, errorCountFrame uint32, errorCountOverflow uint32, err error)

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).

func (*DCBrick)EnableStatusLED()(err error)

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).

func (*DCBrick)DisableStatusLED()(err error)

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).

func (*DCBrick)IsStatusLEDEnabled()(enabled bool, err error)

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

New in version 2.3.1 (Firmware).

func (*DCBrick)GetProtocol1BrickletName(port rune)(protocolVersion uint8, firmwareVersion [3]uint8, name string, err error)

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.

func (*DCBrick)GetChipTemperature()(temperature int16, err error)

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.

func (*DCBrick)Reset()(err error)

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!

func (*DCBrick)GetIdentity()(uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err error)

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.

Callback Configuration Functions

func (*DCBrick)SetMinimumVoltage(voltage uint16)(err error)

Sets the minimum voltage in mV, below which the (*DCBrick) RegisterUnderVoltageCallback 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.

func (*DCBrick)GetMinimumVoltage()(voltage uint16, err error)

Returns the minimum voltage as set by (*DCBrick) SetMinimumVoltage

func (*DCBrick)SetCurrentVelocityPeriod(period uint16)(err error)

Sets a period in ms with which the (*DCBrick) RegisterCurrentVelocityCallback callback is triggered. A period of 0 turns the callback off.

The default value is 0.

func (*DCBrick)GetCurrentVelocityPeriod()(period uint16, err error)

Returns the period as set by (*DCBrick) SetCurrentVelocityPeriod.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding Register*Callback function, which returns a unique callback ID. This ID can be used to deregister the callback later.

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.

func (*DCBrick)RegisterUnderVoltageCallback(func(voltage uint16))(registrationID uint64)

A callback can be registered for this event with the RegisterUnderVoltageCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterUnderVoltageCallback(registrationID uint64) function.

This callback is triggered when the input voltage drops below the value set by (*DCBrick) SetMinimumVoltage. The callback parameter is the current voltage given in mV.

func (*DCBrick)RegisterEmergencyShutdownCallback(func())(registrationID uint64)

A callback can be registered for this event with the RegisterEmergencyShutdownCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterEmergencyShutdownCallback(registrationID uint64) function.

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, (*DCBrick) Enable has to be called to drive the motor again.

Note

This callback only works in Drive/Brake mode (see (*DCBrick) SetDriveMode). In Drive/Coast mode it is unfortunately impossible to reliably read the overcurrent/overtemperature signal from the driver chip.

func (*DCBrick)RegisterVelocityReachedCallback(func(velocity int16))(registrationID uint64)

A callback can be registered for this event with the RegisterVelocityReachedCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterVelocityReachedCallback(registrationID uint64) function.

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 (*DCBrick) RegisterVelocityReachedCallback 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 (*DCBrick) SetAcceleration) 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.

func (*DCBrick)RegisterCurrentVelocityCallback(func(velocity int16))(registrationID uint64)

A callback can be registered for this event with the RegisterCurrentVelocityCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterCurrentVelocityCallback(registrationID uint64) function.

This callback is triggered with the period that is set by (*DCBrick) SetCurrentVelocityPeriod. The callback parameter is the current velocity used by the motor.

The (*DCBrick) RegisterCurrentVelocityCallback callback is only triggered after the set period if there is a change in the velocity.

Constants

dc_brick.DeviceIdentifier

This constant is used to identify a DC Brick.

The (*DCBrick) GetIdentity function and the (*IPConnection) RegisterEnumerateCallback callback of the IPConnection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

dc_brick.DeviceDisplayName

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