This is the description of the Shell API bindings for the Load Cell Bricklet 2.0. General information and technical specifications for the Load Cell Bricklet 2.0 are summarized in its hardware description.
An installation guide for the Shell API bindings is part of their general description.
The example code below is Public Domain (CC0 1.0).
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 2.0
# Get current weight
tinkerforge call load-cell-v2-bricklet $uid get-weight
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Download (example-callback.sh)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | #!/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 2.0
# Handle incoming weight callbacks
tinkerforge dispatch load-cell-v2-bricklet $uid weight &
# Set period for weight callback to 1s (1000ms) without a threshold
tinkerforge call load-cell-v2-bricklet $uid set-weight-callback-configuration 1000 false threshold-option-off 0 0
echo "Press key to exit"; read dummy
kill -- -$$ # Stop callback dispatch in background
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Download (example-threshold.sh)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | #!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this
uid=XYZ # Change XYZ to the UID of your Load Cell Bricklet 2.0
# Handle incoming weight callbacks
tinkerforge dispatch load-cell-v2-bricklet $uid weight &
# Configure threshold for weight "greater than 200 g"
# with a debounce period of 1s (1000ms)
tinkerforge call load-cell-v2-bricklet $uid set-weight-callback-configuration 1000 false threshold-option-greater 200 0
echo "Press key to exit"; read dummy
kill -- -$$ # Stop callback dispatch in background
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Possible exit codes for all tinkerforge commands are:
The common options of the call and dispatch commands are documented here. The specific command structure is shown below.
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The call command is used to call a function of the Load Cell Bricklet 2.0. It can take several options:
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The dispatch command is used to dispatch a callback of the Load Cell Bricklet 2.0. It can take several options:
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The <function> to be called can take different options depending of its kind. All functions can take the following options:
Getter functions can take the following options:
Setter functions can take the following options:
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 send and errors are silently ignored, because they cannot be detected.
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The <callback> to be dispatched can take several options:
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Returns the currently measured weight in grams.
If you want to get the value periodically, it is recommended to use the weight callback. You can set the callback configuration with set-weight-callback-configuration.
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Output: | no output |
Configures the info LED to be either turned off, turned on, or blink in heartbeat mode.
The following symbols are available for this function:
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Returns the LED configuration as set by set-info-led-config
The following symbols are available for this function:
Output: | no output |
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Sets the currently measured weight as tare weight.
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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.
The range for the averaging is 1-100.
The default value is 4.
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Returns the length moving average as set by set-moving-average.
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Output: | no output |
To calibrate your Load Cell Bricklet 2.0 you have to
The calibration is saved in the flash 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.
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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 default rate is 10Hz and the default gain is 128x.
The following symbols are available for this function:
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Returns the configuration as set by set-configuration.
The following symbols are available for this function:
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Returns the error count for the communication between Brick and Bricklet.
The errors are divided into
The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.
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Sets the bootloader mode and returns the status after the requested mode change was instigated.
You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.
This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.
The following symbols are available for this function:
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Returns the current bootloader mode, see set-bootloader-mode.
The following symbols are available for this function:
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Output: | no output |
Sets the firmware pointer for write-firmware. The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).
This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.
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Writes 64 Bytes of firmware at the position as written by set-write-firmware-pointer before. The firmware is written to flash every 4 chunks.
You can only write firmware in bootloader mode.
This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.
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Output: | no output |
Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.
You can also turn the LED permanently on/off or show a heartbeat.
If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.
The following symbols are available for this function:
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Returns the configuration as set by set-status-led-config
The following symbols are available for this function:
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Returns the temperature in °C 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 bad accuracy. Practically it is only useful as an indicator for temperature changes.
Output: | no output |
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Calling this function will reset the Bricklet. All configurations will be lost.
After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!
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Output: | no output |
Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.
We recommend that you use Brick Viewer to change the UID.
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Returns the current UID as an integer. Encode as Base58 to get the usual string version.
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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' or 'd'.
The device identifier numbers can be found here.
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Output: | no output |
The period in ms is the period with which the weight callback is triggered periodically. A value of 0 turns the callback off.
If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.
If it is set to false, the callback is continuously triggered with the period, independent of the value.
It is furthermore possible to constrain the callback with thresholds.
The option-parameter together with min/max sets a threshold for the weight callback.
The following options are possible:
Option | Description |
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'x' | Threshold is turned off |
'o' | Threshold is triggered when the value is outside the min and max values |
'i' | Threshold is triggered when the value is inside or equal to the min and max values |
'<' | Threshold is triggered when the value is smaller than the min value (max is ignored) |
'>' | Threshold is triggered when the value is greater than the min value (max is ignored) |
If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.
The default value is (0, false, 'x', 0, 0).
The following symbols are available for this function:
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Returns the callback configuration as set by set-weight-callback-configuration.
The following symbols are available for this function:
Callbacks can be used to receive time critical or recurring data from the device:
tinkerforge dispatch load-cell-v2-bricklet <uid> example
The available callbacks 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.
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This callback is triggered periodically according to the configuration set by set-weight-callback-configuration.
The parameter is the same as get-weight.