Software / API Bindings / Ruby / API Reference and Examples / Bricklets (Discontinued) / Load Cell Bricklet

Ruby - Load Cell Bricklet¶

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

Examples¶

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

Simple¶

Download (example_simple.rb)

#!/usr/bin/env ruby
# -*- ruby encoding: utf-8 -*-

require 'tinkerforge/ip_connection'
require 'tinkerforge/bricklet_load_cell'

include Tinkerforge

HOST = 'localhost'
PORT = 4223
UID = 'XYZ' # Change XYZ to the UID of your Load Cell Bricklet

ipcon = IPConnection.new # Create IP connection
lc = BrickletLoadCell.new UID, ipcon # Create device object

ipcon.connect HOST, PORT # Connect to brickd
# Don't use device before ipcon is connected

# Get current weight
weight = lc.get_weight
puts "Weight: #{weight} g"

puts 'Press key to exit'
$stdin.gets
ipcon.disconnect

Callback¶

Download (example_callback.rb)

#!/usr/bin/env ruby
# -*- ruby encoding: utf-8 -*-

require 'tinkerforge/ip_connection'
require 'tinkerforge/bricklet_load_cell'

include Tinkerforge

HOST = 'localhost'
PORT = 4223
UID = 'XYZ' # Change XYZ to the UID of your Load Cell Bricklet

ipcon = IPConnection.new # Create IP connection
lc = BrickletLoadCell.new UID, ipcon # Create device object

ipcon.connect HOST, PORT # Connect to brickd
# Don't use device before ipcon is connected

# Register weight callback
lc.register_callback(BrickletLoadCell::CALLBACK_WEIGHT) do |weight|
  puts "Weight: #{weight} g"
end

# Set period for weight callback 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

puts 'Press key to exit'
$stdin.gets
ipcon.disconnect

Threshold¶

Download (example_threshold.rb)

#!/usr/bin/env ruby
# -*- ruby encoding: utf-8 -*-

require 'tinkerforge/ip_connection'
require 'tinkerforge/bricklet_load_cell'

include Tinkerforge

HOST = 'localhost'
PORT = 4223
UID = 'XYZ' # Change XYZ to the UID of your Load Cell Bricklet

ipcon = IPConnection.new # Create IP connection
lc = BrickletLoadCell.new UID, ipcon # Create device object

ipcon.connect HOST, PORT # Connect to brickd
# Don't use device before ipcon is connected

# Get threshold callbacks with a debounce time of 1 second (1000ms)
lc.set_debounce_period 1000

# Register weight reached callback
lc.register_callback(BrickletLoadCell::CALLBACK_WEIGHT_REACHED) do |weight|
  puts "Weight: #{weight} g"
end

# Configure threshold for weight "greater than 200 g"
lc.set_weight_callback_threshold '>', 200, 0

puts 'Press key to exit'
$stdin.gets
ipcon.disconnect

API¶

All functions listed below are thread-safe.

Basic Functions¶

BrickletLoadCell::new(uid, ipcon) → load_cell¶

Parameters:	uid – Type: str ipcon – Type: IPConnection
Returns:	load_cell – Type: BrickletLoadCell

Creates an object with the unique device ID uid:

load_cell = BrickletLoadCell.new 'YOUR_DEVICE_UID', ipcon

This object can then be used after the IP Connection is connected.

BrickletLoadCell#get_weight → int¶

Returns:	weight – Type: int, 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 ::CALLBACK_WEIGHT callback and set the period with #set_weight_callback_period.

BrickletLoadCell#led_on → nil¶: Turns the LED on.

BrickletLoadCell#led_off → nil¶: Turns the LED off.

BrickletLoadCell#is_led_on → bool¶

Returns:	on – Type: bool, Default: false

Returns true if the led is on, false otherwise.

BrickletLoadCell#tare → nil¶: Sets the currently measured weight as tare weight.

Advanced Functions¶

BrickletLoadCell#set_moving_average(average) → nil¶

Parameters:	average – Type: int, 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.

BrickletLoadCell#get_moving_average → int¶

Returns:	average – Type: int, Range: [1 to 40], Default: 4

Returns the length moving average as set by #set_moving_average.

BrickletLoadCell#calibrate(weight) → nil¶

Parameters:	weight – Type: int, 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.

BrickletLoadCell#set_configuration(rate, gain) → nil¶

Parameters:	rate – Type: int, Range: See constants, Default: 0 gain – Type: int, 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 #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:

BrickletLoadCell::RATE_10HZ = 0
BrickletLoadCell::RATE_80HZ = 1

For gain:

BrickletLoadCell::GAIN_128X = 0
BrickletLoadCell::GAIN_64X = 1
BrickletLoadCell::GAIN_32X = 2

BrickletLoadCell#get_configuration → [int, int]¶

Return Array:	0: rate – Type: int, Range: See constants, Default: 0 1: gain – Type: int, Range: See constants, Default: 0

Returns the configuration as set by #set_configuration.

The following constants are available for this function:

For rate:

BrickletLoadCell::RATE_10HZ = 0
BrickletLoadCell::RATE_80HZ = 1

For gain:

BrickletLoadCell::GAIN_128X = 0
BrickletLoadCell::GAIN_64X = 1
BrickletLoadCell::GAIN_32X = 2

BrickletLoadCell#get_identity → [str, str, chr, [int, ...], [int, ...], int]¶

Return Array:

Return Array:	0: uid – Type: str, Length: up to 8 1: connected_uid – Type: str, Length: up to 8 2: position – Type: chr, Range: ['a' to 'h', 'z'] 3: hardware_version – Type: [int, ...], Length: 3 0: major – Type: int, Range: [0 to 255] 1: minor – Type: int, Range: [0 to 255] 2: revision – Type: int, Range: [0 to 255] 4: firmware_version – Type: [int, ...], Length: 3 0: major – Type: int, Range: [0 to 255] 1: minor – Type: int, Range: [0 to 255] 2: revision – Type: int, Range: [0 to 255] 5: device_identifier – Type: int, Range: [0 to 2¹⁶ - 1]

0: uid – Type: str, Length: up to 8
1: connected_uid – Type: str, Length: up to 8
2: position – Type: chr, Range: ['a' to 'h', 'z']
3: hardware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

4: firmware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

5: device_identifier – Type: int, 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). A Bricklet connected to an Isolator Bricklet is always at 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¶

BrickletLoadCell#register_callback(callback_id) { |param [, ...]| block } → nil¶

Parameters:	callback_id – Type: int

Registers the given block with the given callback_id.

The available callback IDs with corresponding function signatures are listed below.

BrickletLoadCell#set_weight_callback_period(period) → nil¶

Parameters:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

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

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

BrickletLoadCell#get_weight_callback_period → int¶

Returns:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by #set_weight_callback_period.

BrickletLoadCell#set_weight_callback_threshold(option, min, max) → nil¶

Parameters:	option – Type: chr, Range: See constants, Default: 'x' min – Type: int, Unit: 1 g, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int, Unit: 1 g, Range: [-2³¹ to 2³¹ - 1], Default: 0

Sets the thresholds for the ::CALLBACK_WEIGHT_REACHED 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:

BrickletLoadCell::THRESHOLD_OPTION_OFF = 'x'
BrickletLoadCell::THRESHOLD_OPTION_OUTSIDE = 'o'
BrickletLoadCell::THRESHOLD_OPTION_INSIDE = 'i'
BrickletLoadCell::THRESHOLD_OPTION_SMALLER = '<'
BrickletLoadCell::THRESHOLD_OPTION_GREATER = '>'

BrickletLoadCell#get_weight_callback_threshold → [chr, int, int]¶

Return Array:	0: option – Type: chr, Range: See constants, Default: 'x' 1: min – Type: int, Unit: 1 g, Range: [-2³¹ to 2³¹ - 1], Default: 0 2: max – Type: int, Unit: 1 g, Range: [-2³¹ to 2³¹ - 1], Default: 0

Returns the threshold as set by #set_weight_callback_threshold.

The following constants are available for this function:

For option:

BrickletLoadCell::THRESHOLD_OPTION_OFF = 'x'
BrickletLoadCell::THRESHOLD_OPTION_OUTSIDE = 'o'
BrickletLoadCell::THRESHOLD_OPTION_INSIDE = 'i'
BrickletLoadCell::THRESHOLD_OPTION_SMALLER = '<'
BrickletLoadCell::THRESHOLD_OPTION_GREATER = '>'

BrickletLoadCell#set_debounce_period(debounce) → nil¶

Parameters:	debounce – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100

Sets the period with which the threshold callback

::CALLBACK_WEIGHT_REACHED

is triggered, if the threshold

#set_weight_callback_threshold

keeps being reached.

BrickletLoadCell#get_debounce_period → int¶

Returns:	debounce – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100

Returns the debounce period as set by #set_debounce_period.

Callbacks¶

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the #register_callback function of the device object. The first parameter is the callback ID and the second parameter is a block:

load_cell.register_callback BrickletLoadCell::CALLBACK_EXAMPLE, do |param|
  puts "#{param}"
end

The available constants with inherent number and type of parameters 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.

BrickletLoadCell::CALLBACK_WEIGHT¶

Callback Parameters:	weight – Type: int, Unit: 1 g, Range: [-2³¹ to 2³¹ - 1]

This callback is triggered periodically with the period that is set by #set_weight_callback_period. The parameter is the weight as measured by the load cell.

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

BrickletLoadCell::CALLBACK_WEIGHT_REACHED¶

Callback Parameters:	weight – Type: int, Unit: 1 g, Range: [-2³¹ to 2³¹ - 1]

This callback is triggered when the threshold as set by #set_weight_callback_threshold is reached. The 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 #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.

BrickletLoadCell#get_api_version → [int, ...]¶

Return Array:	0: api_version – Type: [int, ...], Length: 3 0: major – Type: int, Range: [0 to 255] 1: minor – Type: int, Range: [0 to 255] 2: revision – Type: int, 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.

BrickletLoadCell#get_response_expected(function_id) → bool¶

Parameters:	function_id – Type: int, 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 #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:

BrickletLoadCell::FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
BrickletLoadCell::FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
BrickletLoadCell::FUNCTION_SET_DEBOUNCE_PERIOD = 6
BrickletLoadCell::FUNCTION_SET_MOVING_AVERAGE = 8
BrickletLoadCell::FUNCTION_LED_ON = 10
BrickletLoadCell::FUNCTION_LED_OFF = 11
BrickletLoadCell::FUNCTION_CALIBRATE = 13
BrickletLoadCell::FUNCTION_TARE = 14
BrickletLoadCell::FUNCTION_SET_CONFIGURATION = 15

BrickletLoadCell#set_response_expected(function_id, response_expected) → nil¶

Parameters:	function_id – Type: int, 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.

The following constants are available for this function:

For function_id:

BrickletLoadCell::FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
BrickletLoadCell::FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
BrickletLoadCell::FUNCTION_SET_DEBOUNCE_PERIOD = 6
BrickletLoadCell::FUNCTION_SET_MOVING_AVERAGE = 8
BrickletLoadCell::FUNCTION_LED_ON = 10
BrickletLoadCell::FUNCTION_LED_OFF = 11
BrickletLoadCell::FUNCTION_CALIBRATE = 13
BrickletLoadCell::FUNCTION_TARE = 14
BrickletLoadCell::FUNCTION_SET_CONFIGURATION = 15

BrickletLoadCell#set_response_expected_all(response_expected) → nil¶

Parameters:	response_expected – Type: bool

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

Constants¶

BrickletLoadCell::DEVICE_IDENTIFIER¶

This constant is used to identify a Load Cell Bricklet.

The #get_identity() function and the IPConnection::CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

BrickletLoadCell::DEVICE_DISPLAY_NAME¶: This constant represents the human readable name of a Load Cell Bricklet.