This is the description of the JavaScript 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 JavaScript 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 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | var Tinkerforge = require('tinkerforge');
var HOST = 'localhost';
var PORT = 4223;
var UID = 'XYZ'; // Change XYZ to the UID of your Load Cell Bricklet
var ipcon = new Tinkerforge.IPConnection(); // Create IP connection
var lc = new Tinkerforge.BrickletLoadCell(UID, ipcon); // Create device object
ipcon.connect(HOST, PORT,
function (error) {
console.log('Error: ' + error);
}
); // Connect to brickd
// Don't use device before ipcon is connected
ipcon.on(Tinkerforge.IPConnection.CALLBACK_CONNECTED,
function (connectReason) {
// Get current weight
lc.getWeight(
function (weight) {
console.log('Weight: ' + weight + ' g');
},
function (error) {
console.log('Error: ' + error);
}
);
}
);
console.log('Press key to exit');
process.stdin.on('data',
function (data) {
ipcon.disconnect();
process.exit(0);
}
);
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | var Tinkerforge = require('tinkerforge');
var HOST = 'localhost';
var PORT = 4223;
var UID = 'XYZ'; // Change XYZ to the UID of your Load Cell Bricklet
var ipcon = new Tinkerforge.IPConnection(); // Create IP connection
var lc = new Tinkerforge.BrickletLoadCell(UID, ipcon); // Create device object
ipcon.connect(HOST, PORT,
function (error) {
console.log('Error: ' + error);
}
); // Connect to brickd
// Don't use device before ipcon is connected
ipcon.on(Tinkerforge.IPConnection.CALLBACK_CONNECTED,
function (connectReason) {
// 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.setWeightCallbackPeriod(1000);
}
);
// Register weight callback
lc.on(Tinkerforge.BrickletLoadCell.CALLBACK_WEIGHT,
// Callback function for weight callback
function (weight) {
console.log('Weight: ' + weight + ' g');
}
);
console.log('Press key to exit');
process.stdin.on('data',
function (data) {
ipcon.disconnect();
process.exit(0);
}
);
|
Download (ExampleThreshold.js)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | var Tinkerforge = require('tinkerforge');
var HOST = 'localhost';
var PORT = 4223;
var UID = 'XYZ'; // Change XYZ to the UID of your Load Cell Bricklet
var ipcon = new Tinkerforge.IPConnection(); // Create IP connection
var lc = new Tinkerforge.BrickletLoadCell(UID, ipcon); // Create device object
ipcon.connect(HOST, PORT,
function (error) {
console.log('Error: ' + error);
}
); // Connect to brickd
// Don't use device before ipcon is connected
ipcon.on(Tinkerforge.IPConnection.CALLBACK_CONNECTED,
function (connectReason) {
// Get threshold callbacks with a debounce time of 1 second (1000ms)
lc.setDebouncePeriod(1000);
// Configure threshold for weight "greater than 200 g"
lc.setWeightCallbackThreshold('>', 200, 0);
}
);
// Register weight reached callback
lc.on(Tinkerforge.BrickletLoadCell.CALLBACK_WEIGHT_REACHED,
// Callback function for weight reached callback
function (weight) {
console.log('Weight: ' + weight + ' g');
}
);
console.log('Press key to exit');
process.stdin.on('data',
function (data) {
ipcon.disconnect();
process.exit(0);
}
);
|
Download (ExampleSimple.html), Test (ExampleSimple.html)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | <!DOCTYPE html>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<head>
<title>Tinkerforge | JavaScript Example</title>
</head>
<body>
<div style="text-align:center;">
<h1>Load Cell Bricklet Simple Example</h1>
<p>
<input value="localhost" id="host" type="text" size="20">:
<input value="4280" id="port" type="text" size="5">,
<input value="uid" id="uid" type="text" size="5">
<input value="Start Example" id="start" type="button" onclick="startExample();">
</p>
<p>
<textarea readonly id="text" cols="80" rows="24" style="resize:none;"
>Press "Start Example" to begin ...</textarea>
</p>
</div>
<script src="./Tinkerforge.js" type='text/javascript'></script>
<script type='text/javascript'>
var ipcon;
var textArea = document.getElementById("text");
function startExample() {
textArea.value = "";
var HOST = document.getElementById("host").value;
var PORT = parseInt(document.getElementById("port").value);
var UID = document.getElementById("uid").value;
if(ipcon !== undefined) {
ipcon.disconnect();
}
ipcon = new Tinkerforge.IPConnection(); // Create IP connection
var lc = new Tinkerforge.BrickletLoadCell(UID, ipcon); // Create device object
ipcon.connect(HOST, PORT,
function(error) {
textArea.value += 'Error: ' + error + '\n';
}
); // Connect to brickd
// Don't use device before ipcon is connected
ipcon.on(Tinkerforge.IPConnection.CALLBACK_CONNECTED,
function (connectReason) {
// Get current weight
lc.getWeight(
function (weight) {
textArea.value += 'Weight: ' + weight + ' g\n';
},
function (error) {
textArea.value += 'Error: ' + error + '\n';
}
);
}
);
}
</script>
</body>
</html>
|
Download (ExampleCallback.html), Test (ExampleCallback.html)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 | <!DOCTYPE html>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<head>
<title>Tinkerforge | JavaScript Example</title>
</head>
<body>
<div style="text-align:center;">
<h1>Load Cell Bricklet Callback Example</h1>
<p>
<input value="localhost" id="host" type="text" size="20">:
<input value="4280" id="port" type="text" size="5">,
<input value="uid" id="uid" type="text" size="5">
<input value="Start Example" id="start" type="button" onclick="startExample();">
</p>
<p>
<textarea readonly id="text" cols="80" rows="24" style="resize:none;"
>Press "Start Example" to begin ...</textarea>
</p>
</div>
<script src="./Tinkerforge.js" type='text/javascript'></script>
<script type='text/javascript'>
var ipcon;
var textArea = document.getElementById("text");
function startExample() {
textArea.value = "";
var HOST = document.getElementById("host").value;
var PORT = parseInt(document.getElementById("port").value);
var UID = document.getElementById("uid").value;
if(ipcon !== undefined) {
ipcon.disconnect();
}
ipcon = new Tinkerforge.IPConnection(); // Create IP connection
var lc = new Tinkerforge.BrickletLoadCell(UID, ipcon); // Create device object
ipcon.connect(HOST, PORT,
function(error) {
textArea.value += 'Error: ' + error + '\n';
}
); // Connect to brickd
// Don't use device before ipcon is connected
ipcon.on(Tinkerforge.IPConnection.CALLBACK_CONNECTED,
function (connectReason) {
// 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.setWeightCallbackPeriod(1000);
}
);
// Register weight callback
lc.on(Tinkerforge.BrickletLoadCell.CALLBACK_WEIGHT,
// Callback function for weight callback
function (weight) {
textArea.value += 'Weight: ' + weight + ' g\n';
textArea.scrollTop = textArea.scrollHeight;
}
);
}
</script>
</body>
</html>
|
Download (ExampleThreshold.html), Test (ExampleThreshold.html)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 | <!DOCTYPE html>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<head>
<title>Tinkerforge | JavaScript Example</title>
</head>
<body>
<div style="text-align:center;">
<h1>Load Cell Bricklet Threshold Example</h1>
<p>
<input value="localhost" id="host" type="text" size="20">:
<input value="4280" id="port" type="text" size="5">,
<input value="uid" id="uid" type="text" size="5">
<input value="Start Example" id="start" type="button" onclick="startExample();">
</p>
<p>
<textarea readonly id="text" cols="80" rows="24" style="resize:none;"
>Press "Start Example" to begin ...</textarea>
</p>
</div>
<script src="./Tinkerforge.js" type='text/javascript'></script>
<script type='text/javascript'>
var ipcon;
var textArea = document.getElementById("text");
function startExample() {
textArea.value = "";
var HOST = document.getElementById("host").value;
var PORT = parseInt(document.getElementById("port").value);
var UID = document.getElementById("uid").value;
if(ipcon !== undefined) {
ipcon.disconnect();
}
ipcon = new Tinkerforge.IPConnection(); // Create IP connection
var lc = new Tinkerforge.BrickletLoadCell(UID, ipcon); // Create device object
ipcon.connect(HOST, PORT,
function(error) {
textArea.value += 'Error: ' + error + '\n';
}
); // Connect to brickd
// Don't use device before ipcon is connected
ipcon.on(Tinkerforge.IPConnection.CALLBACK_CONNECTED,
function (connectReason) {
// Get threshold callbacks with a debounce time of 1 second (1000ms)
lc.setDebouncePeriod(1000);
// Configure threshold for weight "greater than 200 g"
lc.setWeightCallbackThreshold('>', 200, 0);
}
);
// Register weight reached callback
lc.on(Tinkerforge.BrickletLoadCell.CALLBACK_WEIGHT_REACHED,
// Callback function for weight reached callback
function (weight) {
textArea.value += 'Weight: ' + weight + ' g\n';
textArea.scrollTop = textArea.scrollHeight;
}
);
}
</script>
</body>
</html>
|
Generally, every function of the JavaScript bindings can take two optional
parameters, returnCallback
and errorCallback
. These are two user
defined callback functions. The returnCallback
function is called with the
results as arguments, if the function returns its results asynchronously. The
errorCallback
is called with an error code in case of an error. The error
code can be one of the following values:
The namespace for the JavaScript bindings is Tinkerforge.*
.
BrickletLoadCell
(uid, ipcon)¶Parameters: |
|
---|---|
Returns: |
|
Creates an object with the unique device ID uid
:
var loadCell = new BrickletLoadCell("YOUR_DEVICE_UID", ipcon);
This object can then be used after the IP Connection is connected.
BrickletLoadCell.
getWeight
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
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
setWeightCallbackPeriod()
.
BrickletLoadCell.
ledOn
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Turns the LED on.
BrickletLoadCell.
ledOff
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Turns the LED off.
BrickletLoadCell.
isLEDOn
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Returns true if the led is on, false otherwise.
BrickletLoadCell.
tare
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Sets the currently measured weight as tare weight.
BrickletLoadCell.
setMovingAverage
(average[, returnCallback][, errorCallback])¶Parameters: |
|
---|---|
Callback Parameters: |
|
Returns: |
|
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.
getMovingAverage
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Returns the length moving average as set by setMovingAverage()
.
BrickletLoadCell.
calibrate
(weight[, returnCallback][, errorCallback])¶Parameters: |
|
---|---|
Callback Parameters: |
|
Returns: |
|
To calibrate your Load Cell Bricklet you have to
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.
setConfiguration
(rate, gain[, returnCallback][, errorCallback])¶Parameters: |
|
---|---|
Callback Parameters: |
|
Returns: |
|
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:
For gain:
BrickletLoadCell.
getConfiguration
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Returns the configuration as set by setConfiguration()
.
The following constants are available for this function:
For rate:
For gain:
BrickletLoadCell.
getIdentity
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
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.
BrickletLoadCell.
on
(callback_id, function[, errorCallback])¶Parameters: |
|
---|---|
Returns: |
|
Registers the given function
with the given callback_id
.
The available callback IDs with corresponding function signatures are listed below.
BrickletLoadCell.
setWeightCallbackPeriod
(period[, returnCallback][, errorCallback])¶Parameters: |
|
---|---|
Callback Parameters: |
|
Returns: |
|
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.
getWeightCallbackPeriod
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Returns the period as set by setWeightCallbackPeriod()
.
BrickletLoadCell.
setWeightCallbackThreshold
(option, min, max[, returnCallback][, errorCallback])¶Parameters: |
|
---|---|
Callback Parameters: |
|
Returns: |
|
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.
getWeightCallbackThreshold
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Returns the threshold as set by setWeightCallbackThreshold()
.
The following constants are available for this function:
For option:
BrickletLoadCell.
setDebouncePeriod
(debounce[, returnCallback][, errorCallback])¶Parameters: |
|
---|---|
Callback Parameters: |
|
Returns: |
|
Sets the period with which the threshold callback
is triggered, if the threshold
keeps being reached.
BrickletLoadCell.
getDebouncePeriod
([returnCallback][, errorCallback])¶Callback Parameters: |
|
---|---|
Returns: |
|
Returns the debounce period as set by setDebouncePeriod()
.
Callbacks can be registered to receive
time critical or recurring data from the device. The registration is done
with the on()
function of
the device object. The first parameter is the callback ID and the second
parameter the callback function:
loadCell.on(BrickletLoadCell.CALLBACK_EXAMPLE,
function (param) {
console.log(param);
}
);
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: |
|
---|
This callback is triggered periodically with the period that is set by
setWeightCallbackPeriod()
. 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: |
|
---|
This callback is triggered when the threshold as set by
setWeightCallbackThreshold()
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 setDebouncePeriod()
.
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.
getAPIVersion
()¶Returns: |
|
---|
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.
getResponseExpected
(functionId[, errorCallback])¶Parameters: |
|
---|---|
Returns: |
|
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 sent and errors are silently ignored, because they cannot be detected.
The following constants are available for this function:
For function_id:
BrickletLoadCell.
setResponseExpected
(functionId, responseExpected[, errorCallback])¶Parameters: |
|
---|---|
Returns: |
|
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:
BrickletLoadCell.
setResponseExpectedAll
(responseExpected)¶Parameters: |
|
---|---|
Returns: |
|
Changes the response expected flag for all setter and callback configuration functions of this device at once.
BrickletLoadCell.
DEVICE_IDENTIFIER
¶This constant is used to identify a Load Cell Bricklet.
The getIdentity()
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.