Node Red State Machine

A finite state machine (FSM) implementation for node red. Displays also a graphical representation of the state machine.
!node-appearance

Installation

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* Via Manage Palette -> Search for "node-red-contrib-finite-statemachine"

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* go to the Node-RED installation folder, in OS X it's usually: ~/.node-red
* run npm install node-red-contrib-finite-statemachine

Usage

You can find detailed usage information in the Usage Manual.

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!node-settings

#### Basic FSM structure
The statemachine of finite state machine is defined by a JSON object within the line FSM (Finite State Machine):

- state holds the initial state. It shall contain a status field.
- transitions holds the possible states as keys (shown as upper case strings). As values it contains one or more key/value pairs, consisting of the transition string (lower case strings) and the resulting state.
- additional data fields are optional. (See Usage Manual)

``json
{
"state": {
"status": "IDLE"
},
"transitions": {
"IDLE": {
"run": "RUNNING"
},
"RUNNING": {
"stop": "IDLE",
"set": "RUNNING"
}
}
}
`

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The input topics of the finite state machine are defined by the transition table setup in the node configuration.

- sending a msg to the node containing a msg.topic set to a defined transition string triggers a state change.
- msg.control= reset sets the machine to its initial state ("state")
- msg.control= sync is used to set the state manually. Its payload needs to be a JSON object, containing a status field
- msg.control= query triggers a state query event and the current state is sent to the output of the state machine. The option Always send state change needs to be enabled for this.

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The output of finite state machine sends a msg whenever there is a valid transition.
Remark: This also may be a valid transition without any state change.

The payload contains:
- status: Outputs the state of the FSM.
- data: Outputs the data object of the FSM. Read more about the data object in the Usage Manual.




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Check Node-REDs info panel to see more information on how to configure the state machine.

Example

*
Remark: Example flows are present in the examples subdirectory. In Node-RED they can be imported via the import function and then selecting Examples in the vertical tab menue.
*

For more examples, read the Usage Manual.

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This example shows a state machine with two states. There is only one msg.topic ("toggleState") which toggles between the two states IDLE and RUNNING.


`json
{
"state": {
"status": "IDLE"
},
"transitions": {
"IDLE": {
"toggleState": "RUNNING"
},
"RUNNING": {
"toggleState": "IDLE"
}
}
}
`
!flow-minimal
MinimalStateMachineFlow.json

Changelog

Changelog.txt




Development

* run npm install
* install grunt npm install -g grunt-cli
* build with npm run build
* create link in node-red folder by running npm install ` within the node-red install directory