PhidgetStepper Class
The PhidgetStepper class is used to control the stepper motors connected to a
PhidgetStepper board. It can be used to set a target position for the motors while
controlling their maximum velocity and acceleration.
Here is a simple example that moves the motor connected to output 0 to its 200 position and then brings it back to position 0. Before making it move, you must first "engage" the motor. Also, you should always explicitely set the desired acceleration and velocity (speed).
var phidgets = require('phidgets');
var ps = new phidgets.PhidgetStepper();
ps.addListener("opened", onReady);
function onReady() {
// Engage motor and set desired properties
ps.engageMotor(0, true);
ps.setAcceleration(0, ps.maximumAcceleration);
ps.setTargetVelocity(0, ps.maximumVelocity);
// Makes the motor move
ps.setTargetPosition(0, 200);
// Triggered when the target position is reached
ps.once("target", function(e, data) {
ps.setTargetPosition(0, 0);
});
}
ps.open();
The PhidgetStepper object adds 5 events to the basic ones inherited by all Phidgets.
They are:
position: triggered each time the motor's position changesstart: triggered when a motor starts movingstop: triggered when a motor stops movingtarget: triggered when the motor has reached its target positioninput: triggered when a digital input changes (not available on all boards)
This object extends the Phidget object which itself extends Node.js'
events.EventEmitter object.
See that object's documentation for more inherited methods and properties.
Constructor
PhidgetStepper
()
Item Index
Methods
Properties
Methods
_forceBetween
-
value -
min -
max
Returns the value after making sure it falls between min and max.
Parameters:
-
valueInt | NumberThe value to check
-
minIntThe minimum value desired
-
maxIntThe maximum value desired
Returns:
int
_handleData
-
chunk
This function is called each time data is received from the Phidget WebSerice. It adds
the data to the input buffer and checks if full lines (separated by '\n') can be
reconstructed. If full lines are found they are handed over to the _parseLineInput()
method for processing.
Parameters:
-
chunkStringA chunk of utf8 encoded text to parse
_makePckString
-
keyword -
[index]
Returns a /PCK string built from the specified parameters. PCK strings are the keys sent out to control the board.
Parameters:
-
keywordStringThe operation keyword to use
-
[index]Int optionalThe index of the output to use
_parseLineInput
-
line
Parses a single line of data typically received from the Phidget WebService. If the
line is a report line, the function hands it off to the _parsePskKey() method.
Otherwise, it deals with it locally.
Parameters:
-
lineStringA non-terminated line of utf8 text
_parsePhidgetSpecificData
-
data
Parses Phidget-specific data received from the Phidget WebService. This function is meant to be overridden by subclasses.
Parameters:
-
dataObjectAn object containing the received data
-
deviceStringThe device identifier (e.g. PhidgetInterfaceKey, PhidgetLED, etc.).
-
labelStringThe custom label set for the device.
-
serialIntThe serial number of the device.
-
keywordStringA keyword identifying the type of information conveyed. It could be 'Input', 'Version', 'DataRate', etc.
-
indexIntThe numerical index (for indexed keys only)
-
valueStringThe actual value.
-
statusStringThe status of the key. It could be: 'added', 'changed', 'removing', etc.
-
_sendLine
-
line
Sends a line of data to the webservice
Parameters:
-
lineStringA non-terminated line of data to send
_sendPck
-
key -
value -
[persistent=false]
Sends the /PCK string (with attached value) to the webservice.
_setPhidgetSpecificInitialState
()
protected
Sets phidget-specific state before the 'opened' event is triggered. This is a good place for subclasses to assign initial values to the board. This is meant to be overridden by subclasses.
addListener
-
event -
listener
This is an alias for the on() method.
close
()
Phidget
chainable
Closes a previously opened connection to a Phidget device.
Returns:
Returns the Phidget to allow method chaining.
engageMotor
-
index -
value
Starts or stops power from being sent to the motor connected to a specific output (or array of outputs). By default, outputs do not power connected motors. Before moving the motor, you must therefore engage the motor first.
To reduce the motor's power consumption, you can disengage it once it's reached its target position. If you are concerned about keeping accurate track of position, the motor should not be disengaged until the motor is stopped.
Parameters:
Returns:
Returns the PhidgetStepper object to allow method chaining.
on
-
event -
listener
Adds a listener to the end of the listeners array for the specified event. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of event and listener will result in the listener being added multiple times.
This method is inherited from Node.js'
events.EventEmitter object.
See that object's documentation for more details methods.
once
-
event -
listener
Adds a one time listener for the event. This listener is invoked only the next time the event is fired, after which it is removed.
This method is inherited from Node.js'
events.EventEmitter object.
See that object's documentation for more details methods.
open
-
[options={}]
Opens a connection to a Phidget device. Opening a connection is a two-step process. First, a connection to the Phidget WebService (which must be running) is established. Then, a session to the specified device (which must be plugged in) is opened.
Parameters:
-
[options={}]Object optionalOptions
Returns:
Returns the Phidget to allow method chaining.
removeAllListeners
-
[event]
Removes all listeners, or those of the specified event.
This method is inherited from Node.js'
events.EventEmitter object.
See that object's documentation for more details methods.
Parameters:
-
[event]String optionalThe event to remove the listeners for.
removeListener
-
[event] -
listener
Removes a listener from the listener array for the specified event. removeListener()
will remove, at most, one instance of a listener from the listener array. If any single
listener has been added multiple times to the listener array for the specified event,
then removeListener() must be called multiple times to remove each instance.
This method is inherited from Node.js'
events.EventEmitter object.
See that object's documentation for more details methods.
setAcceleration
-
index -
[value]
Sets the acceleration for the motor connected to the specified output. The motor will both accelerate and decelarate at this rate. For the 1062 board, this is specified in half-steps.
The minimum and maximum acceleration values can be viewed in the minimumAcceleration
and maximumAcceleration properties.
The acceleration should be explicitely set as part of initialization because otherwise it will remain unknown.
Parameters:
Returns:
Returns the PhidgetStepper to allow method chaining.
setCurrentLimit
-
index -
value
Sets the upper current limit for the motor connected to the specified output. Note that not all stepper controllers support current limiting.
Parameters:
Returns:
Returns the PhidgetStepper to allow method chaining.
setPosition
-
index -
[value]
Sets the current position of the motor connected to the specified output (or array of outputs). Setting the position does not actually move the motor, it merely sets the reference that will be used when moving to a target position.
Parameters:
Returns:
Returns the PhidgetStepper to allow method chaining.
setTargetPosition
-
index -
[value=1000]
Sets a new target position for the motor connected to the specified output. The motor will immediately start moving towards this position.
Note that calling setTargetPosition() will override a previous call to
setTargetPosition() and the motor will begin tracking to the new position
immediately. The velocity of the motor will be ramped appropriately.
Parameters:
Returns:
Returns the PhidgetStepper to allow method chaining.
setTargetVelocity
-
index -
[value]
Sets the target speed (velocity) for the motor connected to the specified output (or
array of outputs). If the targetVelocity is set to 0, the motor will not move.
Note that this is not necessarily the speed that the motor is being turned at. The motor is accelerated towards the target velocity and then decelerated as it approaches the target position. If the target position is close enough, it may never reach the target velocity.
Parameters:
Returns:
Returns the PhidgetStepper to allow method chaining.
Properties
inputs
Object
[read-only] An object containing information about the digital inputs of the
PhidgetStepper board. If PhidgetStepper.inputs.count equals 0, it simply means that
your board does not have any digital inputs.
PhidgetStepper.inputs[0].value // Digital input 0's boolean value
PhidgetStepper.outputs.count // Number of digital inputs on the deviceSub-properties:
-
countIntThe total number of digital inputs on the device.
-
outputs[int].valueBooleanThe current boolean value of the input.
interReportPeriod
Int
The delay (in milliseconds) between report updates sent from the webservice.
Default: 8
label
String
The unique label of the device. The label must have a maximum length of 10 characters. If you try to set a longer label, the remainder will be truncated. Labels are supported only on newer devices and are remembered even when the device is unplugged. A label can only be set after a Phidget has been 'opened'. Trying to set the label before that will fail silently.
Default: undefined
maximumCurrent
Number
[Read-only] The maximum current that an output can be set to. Current limits are not supported by all stepper controllers.
minimumCurrent
Number
[Read-only] The minimum current that an output can be set to. Current limits are not supported by all stepper controllers.
name
String
[read-only] Human-readable version of the board's name (i.e. "Phidget InterfaceKit 8/8/8". This information is only available some time after the connection has been successfully opened.
Default: undefined
outputs
Object
[read-only] An object containing information about the motor outputs of the device. Here are a few examples of how to retrieve information in that object:
PhidgetStepper.outputs[5].currentPosition // Motor 5's current position
PhidgetStepper.outputs[5].stopped // Is motor 5 stopped?
PhidgetStepper.outputs.count // Total number of outputs on the deviceSub-properties:
-
countIntThe total number of outputs on the device.
-
outputs[int].positionNumberThe position of the motor hooked up to that output. This value remains between sessions. It is used when calculating the movement needed to reach the target position. It can be manually set with
setPosition(). -
outputs[int].targetPositionNumberThe last set target position.
-
outputs[int].accelerationNumberThe last set acceleration value (also used as deceleration value). This property should be set as part of initialization because otherwise, it will remain unknown.
-
outputs[int].currentLimitNumberThe last set current limit. Current limit is not supported by all stepper controllers.
-
outputs[int].currentNumberThe actual current draw for the motor connected to that output. Current sense is not supported by all stepper controllers.
-
outputs[int].targetVelocityNumberThe desired velocity (speed) for the motor on that output. Sometimes referred to as the "velocity limit".
-
outputs[int].velocityNumberThe actual current velocity for the motor on that output.
-
outputs[int].engagedBooleanThe engaged state. This is whether or not the motor connected to the output is currently powered.
-
outputs[int].stoppedBooleanWhether the motor connected to that output is currently stopped. If this is true, it indicates that the motor is not moving, and there are no outstanding commands.
password
String
private
The password to connect to the WebService. If specified, it will be used when opening a new connection. As soon as connected the password property will be erased. THIS IS CURRENTLY SET TO PRIVATE BECAUSE IT'S NOT IMPLEMENTED YET!
Default: undefined
port
Int
The port of the Phidgets webservice to connect to.
Default: 5001
ready
Boolean
[read-only] Whether the device is ready for use or not. A device must be 'opened' before it can be used.
reopen
Boolean
Whether to try to automatically reopen the device if it gets remotely closed.
Default: true
serial
Int
The unique serial number of the device. If specified, it will be used to connect to the matching device.
Default: undefined
serverId
Int
[read-only] The unique ID of the Phidget WebService the device is currently connected to.
Default: undefined
updateInterval
Int
The duration (in milliseconds) between update notifications (must be multiple of 8). The shorter the interval is, the more frequent the updates will be sent by the device.
Default: 16
version
String
[read-only] This number distinguishes between revisions of a specific type of Phidget. It is only useful for debugging purposes. This information is only available some time after the connection has been successfully opened.
Default: undefined
Events
closed
Event emitted when the connection to a phidget has been remotely closed.
Event Payload:
-
emitterPhidgetThe actual object that emitted the event.
error
Event emitted when an error occurs while trying to open a phidget
input
Event emitted when digital input data is received.
Event Payload:
-
emitterPhidgetStepperThe actual PhidgetStepper object that emitted the event.
-
dataObjectAn object containing the input data and related information
-
indexIntThe input's index number
-
valueBooleanThe input's received value
-
opened
Event emitted when a phidget is successfully opened.
Event Payload:
-
emitterPhidgetThe actual Phidget object that emitted the event.
opening
Event emitted when an attempt to open a Phidget has been initiated.
Event Payload:
-
emitterPhidgetThe actual Phidget object that emitted the event.
position
Event emitted to report that the position of a motor connected to one of the board's outputs has changed.
Event Payload:
-
emitterPhidgetStepperThe actual PhidgetStepper object that emitted the event.
-
dataObjectAn object containing information about the event.
-
indexIntThe output's index number.
-
indexNumberThe motor's new position.
-
received
private
Event emitted when a new line of data has been received from the web service. This is mostly useful for debugging purposes (hence the @private denomination). It will let you view all data coming in.
reopening
Event emitted when an attempt to automatically re-open a closed Phidget is being carried on.
sent
private
Event emitted when a new line of data has been sent to the Phidget WebService. This is mostly useful for debugging purposes (hence the @private denomination). It will let you view all data going out.
start
Event emitted when a motor connected to one of the board's outputs starts moving.
Event Payload:
-
emitterPhidgetStepperThe actual PhidgetStepper object that emitted the event.
-
dataObjectAn object containing information about the event.
-
indexIntThe output's index number.
-
stop
Event emitted when a motor connected to one of the board's outputs stops moving.
Event Payload:
-
emitterPhidgetStepperThe actual PhidgetStepper object that emitted the event.
-
dataObjectAn object containing information about the event.
-
indexIntThe output's index number.
-
target
Event emitted when a motor connected to one of the board's outputs has reached its target position.
Event Payload:
-
emitterPhidgetStepperThe actual PhidgetStepper object that emitted the event.
-
dataObjectAn object containing information about the event.
-
indexIntThe output's index number.
-
positionIntThe motor's position
-
timeout
Event emitted when an attempt to open a Phidget times out.
Event Payload:
-
emitterPhidgetThe actual Phidget object that emitted the event.