Rust - Load Cell Bricklet

This is the description of the Rust 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 Rust API bindings is part of their general description. Additional documentation can be found on docs.rs.

Examples

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

Simple

Download (example_simple.rs)

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use std::{error::Error, io};

use tinkerforge::{ip_connection::IpConnection, load_cell_bricklet::*};

const HOST: &str = "localhost";
const PORT: u16 = 4223;
const UID: &str = "XYZ"; // Change XYZ to the UID of your Load Cell Bricklet.

fn main() -> Result<(), Box<dyn Error>> {
    let ipcon = IpConnection::new(); // Create IP connection.
    let lc = LoadCellBricklet::new(UID, &ipcon); // Create device object.

    ipcon.connect((HOST, PORT)).recv()??; // Connect to brickd.
                                          // Don't use device before ipcon is connected.

    // Get current weight.
    let weight = lc.get_weight().recv()?;
    println!("Weight: {} g", weight);

    println!("Press enter to exit.");
    let mut _input = String::new();
    io::stdin().read_line(&mut _input)?;
    ipcon.disconnect();
    Ok(())
}

Callback

Download (example_callback.rs)

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use std::{error::Error, io, thread};
use tinkerforge::{ip_connection::IpConnection, load_cell_bricklet::*};

const HOST: &str = "localhost";
const PORT: u16 = 4223;
const UID: &str = "XYZ"; // Change XYZ to the UID of your Load Cell Bricklet.

fn main() -> Result<(), Box<dyn Error>> {
    let ipcon = IpConnection::new(); // Create IP connection.
    let lc = LoadCellBricklet::new(UID, &ipcon); // Create device object.

    ipcon.connect((HOST, PORT)).recv()??; // Connect to brickd.
                                          // Don't use device before ipcon is connected.

    let weight_receiver = lc.get_weight_callback_receiver();

    // Spawn thread to handle received callback messages.
    // This thread ends when the `lc` object
    // is dropped, so there is no need for manual cleanup.
    thread::spawn(move || {
        for weight in weight_receiver {
            println!("Weight: {} g", 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.set_weight_callback_period(1000);

    println!("Press enter to exit.");
    let mut _input = String::new();
    io::stdin().read_line(&mut _input)?;
    ipcon.disconnect();
    Ok(())
}

Threshold

Download (example_threshold.rs)

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use std::{error::Error, io, thread};
use tinkerforge::{ip_connection::IpConnection, load_cell_bricklet::*};

const HOST: &str = "localhost";
const PORT: u16 = 4223;
const UID: &str = "XYZ"; // Change XYZ to the UID of your Load Cell Bricklet.

fn main() -> Result<(), Box<dyn Error>> {
    let ipcon = IpConnection::new(); // Create IP connection.
    let lc = LoadCellBricklet::new(UID, &ipcon); // Create device object.

    ipcon.connect((HOST, PORT)).recv()??; // Connect to brickd.
                                          // Don't use device before ipcon is connected.

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

    let weight_reached_receiver = lc.get_weight_reached_callback_receiver();

    // Spawn thread to handle received callback messages.
    // This thread ends when the `lc` object
    // is dropped, so there is no need for manual cleanup.
    thread::spawn(move || {
        for weight_reached in weight_reached_receiver {
            println!("Weight: {} g", weight_reached);
        }
    });

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

    println!("Press enter to exit.");
    let mut _input = String::new();
    io::stdin().read_line(&mut _input)?;
    ipcon.disconnect();
    Ok(())
}

API

To allow non-blocking usage, nearly every function of the Rust bindings returns a wrapper around a mpsc::Receiver. To block until the function has finished and get your result, call one of the receiver's recv variants. Those return either the result sent by the device, or any error occurred.

Functions returning a result directly will block until the device has finished processing the request.

All functions listed below are thread-safe, those which return a receiver are lock-free.

Basic Functions

pub fn LoadCellBricklet::new(uid: &str, ip_connection: &IpConnection) → LoadCellBricklet
Parameters:
  • uid – Type: &str
  • ip_connection – Type: &IPConnection
Returns:
  • load_cell – Type: LoadCellBricklet

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

let load_cell = LoadCellBricklet::new("YOUR_DEVICE_UID", &ip_connection);

This device object can be used after the IP connection has been connected.

pub fn LoadCellBricklet::get_weight(&self) → ConvertingReceiver<i32>
Returns:
  • weight – Type: i32, Unit: 1 g, Range: [-231 to 231 - 1]

Returns the currently measured weight.

If you want to get the weight periodically, it is recommended to use the LoadCellBricklet::get_weight_callback_receiver callback and set the period with LoadCellBricklet::set_weight_callback_period.

pub fn LoadCellBricklet::led_on(&self) → ConvertingReceiver<()>

Turns the LED on.

pub fn LoadCellBricklet::led_off(&self) → ConvertingReceiver<()>

Turns the LED off.

pub fn LoadCellBricklet::is_led_on(&self) → ConvertingReceiver<bool>
Returns:
  • on – Type: bool, Default: false

Returns true if the led is on, false otherwise.

pub fn LoadCellBricklet::tare(&self) → ConvertingReceiver<()>

Sets the currently measured weight as tare weight.

Advanced Functions

pub fn LoadCellBricklet::set_moving_average(&self, average: u8) → ConvertingReceiver<()>
Parameters:
  • average – Type: u8, Range: [1 to 40], Default: 4

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.

pub fn LoadCellBricklet::get_moving_average(&self) → ConvertingReceiver<u8>
Returns:
  • average – Type: u8, Range: [1 to 40], Default: 4

Returns the length moving average as set by LoadCellBricklet::set_moving_average.

pub fn LoadCellBricklet::calibrate(&self, weight: u32) → ConvertingReceiver<()>
Parameters:
  • weight – Type: u32, Unit: 1 g, Range: [0 to 232 - 1]

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.

pub fn LoadCellBricklet::set_configuration(&self, rate: u8, gain: u8) → ConvertingReceiver<()>
Parameters:
  • rate – Type: u8, Range: See constants, Default: 0
  • gain – Type: u8, Range: See constants, Default: 0

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 LoadCellBricklet::set_moving_average) 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_RATE_10HZ = 0
  • LOAD_CELL_BRICKLET_RATE_80HZ = 1

For gain:

  • LOAD_CELL_BRICKLET_GAIN_128X = 0
  • LOAD_CELL_BRICKLET_GAIN_64X = 1
  • LOAD_CELL_BRICKLET_GAIN_32X = 2
pub fn LoadCellBricklet::get_configuration(&self) → ConvertingReceiver<Configuration>
Return Object:
  • rate – Type: u8, Range: See constants, Default: 0
  • gain – Type: u8, Range: See constants, Default: 0

Returns the configuration as set by LoadCellBricklet::set_configuration.

The following constants are available for this function:

For rate:

  • LOAD_CELL_BRICKLET_RATE_10HZ = 0
  • LOAD_CELL_BRICKLET_RATE_80HZ = 1

For gain:

  • LOAD_CELL_BRICKLET_GAIN_128X = 0
  • LOAD_CELL_BRICKLET_GAIN_64X = 1
  • LOAD_CELL_BRICKLET_GAIN_32X = 2
pub fn LoadCellBricklet::get_identity(&self) → ConvertingReceiver<Identity>
Return Object:
  • uid – Type: String, Length: up to 8
  • connected_uid – Type: String, Length: up to 8
  • position – Type: char, Range: ['a' to 'h', 'i', 'z']
  • hardware_version – Type: [u8; 3]
    • 0: major – Type: u8, Range: [0 to 255]
    • 1: minor – Type: u8, Range: [0 to 255]
    • 2: revision – Type: u8, Range: [0 to 255]
  • firmware_version – Type: [u8; 3]
    • 0: major – Type: u8, Range: [0 to 255]
    • 1: minor – Type: u8, Range: [0 to 255]
    • 2: revision – Type: u8, Range: [0 to 255]
  • device_identifier – Type: u16, Range: [0 to 216 - 1]

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

pub fn LoadCellBricklet::set_weight_callback_period(&self, period: u32) → ConvertingReceiver<()>
Parameters:
  • period – Type: u32, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

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

The LoadCellBricklet::get_weight_callback_receiver callback is only triggered if the weight has changed since the last triggering.

pub fn LoadCellBricklet::get_weight_callback_period(&self) → ConvertingReceiver<u32>
Returns:
  • period – Type: u32, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by LoadCellBricklet::set_weight_callback_period.

pub fn LoadCellBricklet::set_weight_callback_threshold(&self, option: char, min: i32, max: i32) → ConvertingReceiver<()>
Parameters:
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: i32, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0
  • max – Type: i32, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0

Sets the thresholds for the LoadCellBricklet::get_weight_reached_callback_receiver 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_THRESHOLD_OPTION_OFF = 'x'
  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_OUTSIDE = 'o'
  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_INSIDE = 'i'
  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_SMALLER = '<'
  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_GREATER = '>'
pub fn LoadCellBricklet::get_weight_callback_threshold(&self) → ConvertingReceiver<WeightCallbackThreshold>
Return Object:
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: i32, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0
  • max – Type: i32, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0

Returns the threshold as set by LoadCellBricklet::set_weight_callback_threshold.

The following constants are available for this function:

For option:

  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_OFF = 'x'
  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_OUTSIDE = 'o'
  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_INSIDE = 'i'
  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_SMALLER = '<'
  • LOAD_CELL_BRICKLET_THRESHOLD_OPTION_GREATER = '>'
pub fn LoadCellBricklet::set_debounce_period(&self, debounce: u32) → ConvertingReceiver<()>
Parameters:
  • debounce – Type: u32, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

Sets the period with which the threshold callback

is triggered, if the threshold

keeps being reached.

pub fn LoadCellBricklet::get_debounce_period(&self) → ConvertingReceiver<u32>
Returns:
  • debounce – Type: u32, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

Returns the debounce period as set by LoadCellBricklet::set_debounce_period.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding get_*_callback_receiver function, which returns a receiver for callback events.

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.

pub fn LoadCellBricklet::get_weight_callback_receiver(&self) → ConvertingCallbackReceiver<i32>
Event:
  • weight – Type: i32, Unit: 1 g, Range: [-231 to 231 - 1]

Receivers created with this function receive Weight events.

This callback is triggered periodically with the period that is set by LoadCellBricklet::set_weight_callback_period. The received variable is the weight as measured by the load cell.

The LoadCellBricklet::get_weight_callback_receiver callback is only triggered if the weight has changed since the last triggering.

pub fn LoadCellBricklet::get_weight_reached_callback_receiver(&self) → ConvertingCallbackReceiver<i32>
Event:
  • weight – Type: i32, Unit: 1 g, Range: [-231 to 231 - 1]

Receivers created with this function receive Weight Reached events.

This callback is triggered when the threshold as set by LoadCellBricklet::set_weight_callback_threshold is reached. The received variable 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 LoadCellBricklet::set_debounce_period.

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.

pub fn LoadCellBricklet::get_api_version(&self) → [u8; 3]
Return Object:
  • api_version – Type: [u8; 3]
    • 0: major – Type: u8, Range: [0 to 255]
    • 1: minor – Type: u8, Range: [0 to 255]
    • 2: revision – Type: u8, Range: [0 to 255]

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.

pub fn LoadCellBricklet::get_response_expected(&mut self, function_id: u8) → bool
Parameters:
  • function_id – Type: u8, Range: See constants
Returns:
  • response_expected – Type: bool

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 LoadCellBricklet::set_response_expected. 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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • LOAD_CELL_BRICKLET_FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
  • LOAD_CELL_BRICKLET_FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
  • LOAD_CELL_BRICKLET_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • LOAD_CELL_BRICKLET_FUNCTION_SET_MOVING_AVERAGE = 8
  • LOAD_CELL_BRICKLET_FUNCTION_LED_ON = 10
  • LOAD_CELL_BRICKLET_FUNCTION_LED_OFF = 11
  • LOAD_CELL_BRICKLET_FUNCTION_CALIBRATE = 13
  • LOAD_CELL_BRICKLET_FUNCTION_TARE = 14
  • LOAD_CELL_BRICKLET_FUNCTION_SET_CONFIGURATION = 15
pub fn LoadCellBricklet::set_response_expected(&mut self, function_id: u8, response_expected: bool) → ()
Parameters:
  • function_id – Type: u8, Range: See constants
  • response_expected – Type: bool

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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • LOAD_CELL_BRICKLET_FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
  • LOAD_CELL_BRICKLET_FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
  • LOAD_CELL_BRICKLET_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • LOAD_CELL_BRICKLET_FUNCTION_SET_MOVING_AVERAGE = 8
  • LOAD_CELL_BRICKLET_FUNCTION_LED_ON = 10
  • LOAD_CELL_BRICKLET_FUNCTION_LED_OFF = 11
  • LOAD_CELL_BRICKLET_FUNCTION_CALIBRATE = 13
  • LOAD_CELL_BRICKLET_FUNCTION_TARE = 14
  • LOAD_CELL_BRICKLET_FUNCTION_SET_CONFIGURATION = 15
pub fn LoadCellBricklet::set_response_expected_all(&mut self, response_expected: bool) → ()
Parameters:
  • response_expected – Type: bool

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

Constants

pub const LoadCellBricklet::DEVICE_IDENTIFIER

This constant is used to identify a Load Cell Bricklet.

The LoadCellBricklet::get_identity function and the IpConnection::get_enumerate_callback_receiver callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

pub const LoadCellBricklet::DEVICE_DISPLAY_NAME

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