Go - Load Cell Bricklet

This is the description of the Go API bindings for the Load Cell Bricklet. General information and technical specifications for the Load Cell Bricklet 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).

Simple

Download (example_simple.go)

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package main

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

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Load Cell Bricklet.

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

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

    // Get current weight.
    weight, _ := lc.GetWeight()
    fmt.Printf("Weight:  g\n", weight)

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

Callback

Download (example_callback.go)

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package main

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

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Load Cell Bricklet.

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

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

    lc.RegisterWeightCallback(func(weight int32) {
        fmt.Printf("Weight: %d g\n", weight)
    })

    // Set period for weight receiver to 1s (1000ms).
    // Note: The weight callback is only called every second
    //       if the weight has changed since the last call!
    lc.SetWeightCallbackPeriod(1000)

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

Threshold

Download (example_threshold.go)

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package main

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

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Load Cell Bricklet.

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

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

    // Get threshold receivers with a debounce time of 1 second (1000ms).
    lc.SetDebouncePeriod(1000)

    lc.RegisterWeightReachedCallback(func(weight int32) {
        fmt.Printf("Weight: %d g\n", weight)
    })

    // Configure threshold for weight "greater than 200 g".
    lc.SetWeightCallbackThreshold('>', 200, 0)

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

API

The Load Cell Bricklet API is defined in the package github.com/Tinkerforge/go-api-bindings/load_cell_bricklet

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

  • ipconnection.DeviceErrorSuccess = 0
  • ipconnection.DeviceErrorInvalidParameter = 1
  • ipconnection.DeviceErrorFunctionNotSupported = 2
  • ipconnection.DeviceErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions

func load_cell_bricklet.New(uid string, ipcon *IPConnection) (device LoadCellBricklet, err error)
Parameters:
  • uid – Type: string
  • ipcon – Type: *IPConnection
Returns:
  • device – Type: LoadCellBricklet
  • err – Type: error

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

device, err := load_cell_bricklet.New("YOUR_DEVICE_UID", &ipcon)

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

func (*LoadCellBricklet) GetWeight() (weight int32, err error)
Returns:
  • weight – Type: int32, Unit: 1 g, Range: [-231 to 231 - 1]
  • err – Type: error

Returns the currently measured weight.

If you want to get the weight periodically, it is recommended to use the RegisterWeightCallback callback and set the period with SetWeightCallbackPeriod().

func (*LoadCellBricklet) LEDOn() (err error)
Returns:
  • err – Type: error

Turns the LED on.

func (*LoadCellBricklet) LEDOff() (err error)
Returns:
  • err – Type: error

Turns the LED off.

func (*LoadCellBricklet) IsLEDOn() (on bool, err error)
Returns:
  • on – Type: bool, Default: false
  • err – Type: error

Returns true if the led is on, false otherwise.

func (*LoadCellBricklet) Tare() (err error)
Returns:
  • err – Type: error

Sets the currently measured weight as tare weight.

Advanced Functions

func (*LoadCellBricklet) SetMovingAverage(average uint8) (err error)
Parameters:
  • average – Type: uint8, Range: [1 to 40], Default: 4
Returns:
  • err – Type: error

Sets the length of a moving averaging for the weight value.

Setting the length to 1 will turn the averaging off. With less averaging, there is more noise on the data.

func (*LoadCellBricklet) GetMovingAverage() (average uint8, err error)
Returns:
  • average – Type: uint8, Range: [1 to 40], Default: 4
  • err – Type: error

Returns the length moving average as set by SetMovingAverage().

func (*LoadCellBricklet) Calibrate(weight uint32) (err error)
Parameters:
  • weight – Type: uint32, Unit: 1 g, Range: [0 to 232 - 1]
Returns:
  • err – Type: error

To calibrate your Load Cell Bricklet you have to

  • empty the scale and call this function with 0 and
  • add a known weight to the scale and call this function with the weight.

The calibration is saved in the EEPROM of the Bricklet and only needs to be done once.

We recommend to use the Brick Viewer for calibration, you don't need to call this function in your source code.

func (*LoadCellBricklet) SetConfiguration(rate uint8, gain uint8) (err error)
Parameters:
  • rate – Type: uint8, Range: See constants, Default: 0
  • gain – Type: uint8, Range: See constants, Default: 0
Returns:
  • err – Type: error

The measurement rate and gain are configurable.

The rate can be either 10Hz or 80Hz. A faster rate will produce more noise. It is additionally possible to add a moving average (see SetMovingAverage()) to the measurements.

The gain can be 128x, 64x or 32x. It represents a measurement range of ±20mV, ±40mV and ±80mV respectively. The Load Cell Bricklet uses an excitation voltage of 5V and most load cells use an output of 2mV/V. That means the voltage range is ±15mV for most load cells (i.e. gain of 128x is best). If you don't know what all of this means you should keep it at 128x, it will most likely be correct.

The configuration is saved in the EEPROM of the Bricklet and only needs to be done once.

We recommend to use the Brick Viewer for configuration, you don't need to call this function in your source code.

The following constants are available for this function:

For rate:

  • load_cell_bricklet.Rate10Hz = 0
  • load_cell_bricklet.Rate80Hz = 1

For gain:

  • load_cell_bricklet.Gain128x = 0
  • load_cell_bricklet.Gain64x = 1
  • load_cell_bricklet.Gain32x = 2
func (*LoadCellBricklet) GetConfiguration() (rate uint8, gain uint8, err error)
Returns:
  • rate – Type: uint8, Range: See constants, Default: 0
  • gain – Type: uint8, Range: See constants, Default: 0
  • err – Type: error

Returns the configuration as set by SetConfiguration().

The following constants are available for this function:

For rate:

  • load_cell_bricklet.Rate10Hz = 0
  • load_cell_bricklet.Rate80Hz = 1

For gain:

  • load_cell_bricklet.Gain128x = 0
  • load_cell_bricklet.Gain64x = 1
  • load_cell_bricklet.Gain32x = 2
func (*LoadCellBricklet) GetIdentity() (uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err error)
Returns:
  • uid – Type: string, Length: up to 8
  • connectedUid – Type: string, Length: up to 8
  • position – Type: rune, Range: ['a' to 'h', 'i', 'z']
  • hardwareVersion – Type: [3]uint8
    • 0: major – Type: uint8, Range: [0 to 255]
    • 1: minor – Type: uint8, Range: [0 to 255]
    • 2: revision – Type: uint8, Range: [0 to 255]
  • firmwareVersion – Type: [3]uint8
    • 0: major – Type: uint8, Range: [0 to 255]
    • 1: minor – Type: uint8, Range: [0 to 255]
    • 2: revision – Type: uint8, Range: [0 to 255]
  • deviceIdentifier – Type: uint16, Range: [0 to 216 - 1]
  • err – Type: error

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as position 'z'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

func (*LoadCellBricklet) SetWeightCallbackPeriod(period uint32) (err error)
Parameters:
  • period – Type: uint32, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
Returns:
  • err – Type: error

Sets the period with which the RegisterWeightCallback callback is triggered periodically. A value of 0 turns the callback off.

The RegisterWeightCallback callback is only triggered if the weight has changed since the last triggering.

func (*LoadCellBricklet) GetWeightCallbackPeriod() (period uint32, err error)
Returns:
  • period – Type: uint32, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • err – Type: error

Returns the period as set by SetWeightCallbackPeriod().

func (*LoadCellBricklet) SetWeightCallbackThreshold(option rune, min int32, max int32) (err error)
Parameters:
  • option – Type: rune, Range: See constants, Default: 'x'
  • min – Type: int32, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0
  • max – Type: int32, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0
Returns:
  • err – Type: error

Sets the thresholds for the RegisterWeightReachedCallback callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the weight is outside the min and max values
'i' Callback is triggered when the weight is inside the min and max values
'<' Callback is triggered when the weight is smaller than the min value (max is ignored)
'>' Callback is triggered when the weight is greater than the min value (max is ignored)

The following constants are available for this function:

For option:

  • load_cell_bricklet.ThresholdOptionOff = 'x'
  • load_cell_bricklet.ThresholdOptionOutside = 'o'
  • load_cell_bricklet.ThresholdOptionInside = 'i'
  • load_cell_bricklet.ThresholdOptionSmaller = '<'
  • load_cell_bricklet.ThresholdOptionGreater = '>'
func (*LoadCellBricklet) GetWeightCallbackThreshold() (option rune, min int32, max int32, err error)
Returns:
  • option – Type: rune, Range: See constants, Default: 'x'
  • min – Type: int32, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0
  • max – Type: int32, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0
  • err – Type: error

Returns the threshold as set by SetWeightCallbackThreshold().

The following constants are available for this function:

For option:

  • load_cell_bricklet.ThresholdOptionOff = 'x'
  • load_cell_bricklet.ThresholdOptionOutside = 'o'
  • load_cell_bricklet.ThresholdOptionInside = 'i'
  • load_cell_bricklet.ThresholdOptionSmaller = '<'
  • load_cell_bricklet.ThresholdOptionGreater = '>'
func (*LoadCellBricklet) SetDebouncePeriod(debounce uint32) (err error)
Parameters:
  • debounce – Type: uint32, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100
Returns:
  • err – Type: error

Sets the period with which the threshold callback

is triggered, if the threshold

keeps being reached.

func (*LoadCellBricklet) GetDebouncePeriod() (debounce uint32, err error)
Returns:
  • debounce – Type: uint32, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100
  • err – Type: error

Returns the debounce period as set by SetDebouncePeriod().

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 with the corresponding Deregister*Callback function.

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 (*LoadCellBricklet) RegisterWeightCallback(func(weight int32)) (registrationId uint64)
Callback Parameters:
  • weight – Type: int32, Unit: 1 g, Range: [-231 to 231 - 1]
Returns:
  • registrationId – Type: uint64

This callback is triggered periodically with the period that is set by SetWeightCallbackPeriod(). The callback parameter is the weight as measured by the load cell.

The RegisterWeightCallback callback is only triggered if the weight has changed since the last triggering.

func (*LoadCellBricklet) RegisterWeightReachedCallback(func(weight int32)) (registrationId uint64)
Callback Parameters:
  • weight – Type: int32, Unit: 1 g, Range: [-231 to 231 - 1]
Returns:
  • registrationId – Type: uint64

This callback is triggered when the threshold as set by SetWeightCallbackThreshold() is reached. The callback parameter is the weight as measured by the load cell.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by SetDebouncePeriod().

Virtual Functions

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

func (*LoadCellBricklet) GetAPIVersion() (apiVersion [3]uint8, err error)
Returns:
  • apiVersion – Type: [3]uint8
    • 0: major – Type: uint8, Range: [0 to 255]
    • 1: minor – Type: uint8, Range: [0 to 255]
    • 2: revision – Type: uint8, Range: [0 to 255]
  • err – Type: error

Returns the version of the API definition 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 (*LoadCellBricklet) GetResponseExpected(functionId uint8) (responseExpected bool, err error)
Parameters:
  • functionId – Type: uint8, Range: See constants
Returns:
  • responseExpected – Type: bool
  • err – Type: 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 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.

The following constants are available for this function:

For functionId:

  • load_cell_bricklet.FunctionSetWeightCallbackPeriod = 2
  • load_cell_bricklet.FunctionSetWeightCallbackThreshold = 4
  • load_cell_bricklet.FunctionSetDebouncePeriod = 6
  • load_cell_bricklet.FunctionSetMovingAverage = 8
  • load_cell_bricklet.FunctionLEDOn = 10
  • load_cell_bricklet.FunctionLEDOff = 11
  • load_cell_bricklet.FunctionCalibrate = 13
  • load_cell_bricklet.FunctionTare = 14
  • load_cell_bricklet.FunctionSetConfiguration = 15
func (*LoadCellBricklet) SetResponseExpected(functionId uint8, responseExpected bool) (err error)
Parameters:
  • functionId – Type: uint8, Range: See constants
  • responseExpected – Type: bool
Returns:
  • err – Type: 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 constants are available for this function:

For functionId:

  • load_cell_bricklet.FunctionSetWeightCallbackPeriod = 2
  • load_cell_bricklet.FunctionSetWeightCallbackThreshold = 4
  • load_cell_bricklet.FunctionSetDebouncePeriod = 6
  • load_cell_bricklet.FunctionSetMovingAverage = 8
  • load_cell_bricklet.FunctionLEDOn = 10
  • load_cell_bricklet.FunctionLEDOff = 11
  • load_cell_bricklet.FunctionCalibrate = 13
  • load_cell_bricklet.FunctionTare = 14
  • load_cell_bricklet.FunctionSetConfiguration = 15
func (*LoadCellBricklet) SetResponseExpectedAll(responseExpected bool) (err error)
Parameters:
  • responseExpected – Type: bool
Returns:
  • err – Type: error

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

Constants

load_cell_bricklet.DeviceIdentifier

This constant is used to identify a Load Cell Bricklet.

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

load_cell_bricklet.DeviceDisplayName

This constant represents the human readable name of a Load Cell Bricklet.