Shell - Load Cell Bricklet¶

Simple¶

Download (example-simple.sh)

1
2
3
4
5
6
7

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

uid=XYZ # Change XYZ to the UID of your Load Cell Bricklet

# Get current weight
tinkerforge call load-cell-bricklet $uid get-weight

Callback¶

Download (example-callback.sh)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16

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

uid=XYZ # Change XYZ to the UID of your Load Cell Bricklet

# Handle incoming weight callbacks
tinkerforge dispatch load-cell-bricklet $uid weight &

# 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!
tinkerforge call load-cell-bricklet $uid set-weight-callback-period 1000

echo "Press key to exit"; read dummy

kill -- -$$ # Stop callback dispatch in background

Threshold¶

Download (example-threshold.sh)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17

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

uid=XYZ # Change XYZ to the UID of your Load Cell Bricklet

# Get threshold callbacks with a debounce time of 1 second (1000ms)
tinkerforge call load-cell-bricklet $uid set-debounce-period 1000

# Handle incoming weight reached callbacks
tinkerforge dispatch load-cell-bricklet $uid weight-reached &

# Configure threshold for weight "greater than 200 g"
tinkerforge call load-cell-bricklet $uid set-weight-callback-threshold threshold-option-greater 200 0

echo "Press key to exit"; read dummy

kill -- -$$ # Stop callback dispatch in background

Command Structure¶

The common options of the call and dispatch commands are documented here. The specific command structure is shown below.

tinkerforge call load-cell-bricklet [<option>..] <uid> <function> [<argument>..]¶

Parameters:	<uid> – Type: String <function> – Type: String

The call command is used to call a function of the Load Cell Bricklet. 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 Load Cell Bricklet and exits

tinkerforge dispatch load-cell-bricklet [<option>..] <uid> <callback>¶

Parameters:	<uid> – Type: String <callback> – Type: String

The dispatch command is used to dispatch a callback of the Load Cell Bricklet. 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 Load Cell Bricklet and exits

tinkerforge call load-cell-bricklet <uid> <function> [<option>..] [<argument>..]¶

Parameters:	<uid> – Type: String <function> – Type: 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 sent and errors are silently ignored, because they cannot be detected.

tinkerforge dispatch load-cell-bricklet <uid> <callback> [<option>..]¶

Parameters:	<uid> – Type: String <callback> – Type: 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 load-cell-bricklet <uid> get-weight¶

Output:	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 weight callback and set the period with set-weight-callback-period.

tinkerforge call load-cell-bricklet <uid> led-on¶

Output:	no output

Turns the LED on.

tinkerforge call load-cell-bricklet <uid> led-off¶

Output:	no output

Turns the LED off.

tinkerforge call load-cell-bricklet <uid> is-led-on¶

Output:	on – Type: Bool, Default: false

Returns true if the led is on, false otherwise.

tinkerforge call load-cell-bricklet <uid> tare¶

Output:	no output

Sets the currently measured weight as tare weight.

Advanced Functions¶

tinkerforge call load-cell-bricklet <uid> set-moving-average <average>¶

Parameters:	<average> – Type: Int, Range: [1 to 40], Default: 4
Output:	no output

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.

tinkerforge call load-cell-bricklet <uid> get-moving-average¶

Output:	average – Type: Int, Range: [1 to 40], Default: 4

Returns the length moving average as set by set-moving-average.

tinkerforge call load-cell-bricklet <uid> calibrate <weight>¶

Parameters:	<weight> – Type: Int, Unit: 1 g, Range: [0 to 232 - 1]
Output:	no output

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.

tinkerforge call load-cell-bricklet <uid> set-configuration <rate> <gain>¶

Parameters:	<rate> – Type: Int, Range: See symbols, Default: 0 <gain> – Type: Int, Range: See symbols, Default: 0
Output:	no output

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 symbols are available for this function:

For <rate>:

• rate-10hz = 0
• rate-80hz = 1

For <gain>:

• gain-128x = 0
• gain-64x = 1
• gain-32x = 2

tinkerforge call load-cell-bricklet <uid> get-configuration¶

Output:	rate – Type: Int, Range: See symbols, Default: 0 gain – Type: Int, Range: See symbols, Default: 0

Returns the configuration as set by set-configuration.

The following symbols are available for this function:

For rate:

• rate-10hz = 0
• rate-80hz = 1

For gain:

• gain-128x = 0
• gain-64x = 1
• gain-32x = 2

tinkerforge call load-cell-bricklet <uid> get-identity¶

Output:

uid – Type: String, Length: up to 8 connected-uid – Type: String, Length: up to 8 position – Type: Char, Range: [a to h, z] hardware-version – Type: Int Array, 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] firmware-version – Type: Int Array, 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] 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. 

Callback Configuration Functions¶

tinkerforge call load-cell-bricklet <uid> set-weight-callback-period <period>¶

Parameters:	<period> – Type: Int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
Output:	no output

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

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

tinkerforge call load-cell-bricklet <uid> get-weight-callback-period¶

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

Returns the period as set by set-weight-callback-period.

tinkerforge call load-cell-bricklet <uid> set-weight-callback-threshold <option> <min> <max>¶

Parameters:	<option> – Type: Char, Range: See symbols, 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
Output:	no output

Sets the thresholds for the 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 symbols are available for this function:

For <option>:

• threshold-option-off = x
• threshold-option-outside = o
• threshold-option-inside = i
• threshold-option-smaller = <
• threshold-option-greater = >

tinkerforge call load-cell-bricklet <uid> get-weight-callback-threshold¶

Output:	option – Type: Char, Range: See symbols, 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

Returns the threshold as set by set-weight-callback-threshold.

The following symbols are available for this function:

For option:

• threshold-option-off = x
• threshold-option-outside = o
• threshold-option-inside = i
• threshold-option-smaller = <
• threshold-option-greater = >

tinkerforge call load-cell-bricklet <uid> set-debounce-period <debounce>¶

Parameters:	<debounce> – Type: Int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100
Output:	no output

Sets the period with which the threshold callback

• weight-reached

is triggered, if the threshold

• set-weight-callback-threshold

keeps being reached.

tinkerforge call load-cell-bricklet <uid> get-debounce-period¶

Output:	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 used to receive time critical or recurring data from the device:

tinkerforge dispatch load-cell-bricklet <uid> example

The available callbacks are described below.

tinkerforge dispatch load-cell-bricklet <uid> weight¶

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

tinkerforge dispatch load-cell-bricklet <uid> weight-reached¶

Output:	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.