Simple step through outputs on trigger

General
1

Hi,
I have what I think should be really simple challenge, but am struggling.

I want to setup a flow where each time the flow is triggered it triggers the next output in a sequence

I can do with a complex if then else in a function node, but it is not very elegant.

The use case is using a single button to trigger different radio channels to be played.
so each time you press, it switches to the next channel in a set list and when it gets to the last it restarts.

I'm sure there must be cone neat way to achieve this.

Any suggestions?

2

If your list of channels is in an array, you just need to increment a counter (and reset it when it points to a nonexistant array element)

Probably use a flow context variable for the counter.

3

Thanks, I could lok at that, i'm surprised that there isn't a state machine module that works like this.

4

Solved it with a function variable followed by a switch node.

if (flow.get("channel") == 6){
    flow.set("channel",4);
}else if (flow.get("channel") == 4){
    flow.set("channel",3);
}else if(flow.get("channel") == 3){
    flow.set("channel",6);
}
else{
    flow.set("channel",6);
}  
return msg;
5

There are several state machine nodes in the node-red flows library.

6

I know, but cant get my head around how I would achieve this functionality

7

Use the button trigger to step you through the states in whatever machine you are using. Personally I would just use a Function node, I think it is easier than using a state machine node.

const channels = [6, 4, 3]
let currentIndex = context.get("currentIndex") || 0
currentIndex = currentIndex + 1
if (currentIndex >= channels.length) {
    currentIndex = 0
}
msg.payload = channels[currentIndex]
node.status( `Channel ${msg.payload}` )
context.set("currentIndex", currentIndex)
return msg;

[{"id":"804aa6bce11220c3","type":"inject","z":"bdd7be38.d3b55","name":"Button simulator","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":180,"y":3280,"wires":[["a1d8ae260177640c"]]},{"id":"a1d8ae260177640c","type":"function","z":"bdd7be38.d3b55","name":"Cycle channels","func":"const channels = [6, 4, 3]\nlet currentIndex = context.get(\"currentIndex\") || 0\ncurrentIndex = currentIndex + 1\nif (currentIndex >= channels.length) {\n    currentIndex = 0\n}\nmsg.payload = channels[currentIndex]\nnode.status( `Channel ${msg.payload}` )\ncontext.set(\"currentIndex\", currentIndex)\nreturn msg;","outputs":1,"timeout":0,"noerr":0,"initialize":"","finalize":"","libs":[],"x":420,"y":3280,"wires":[["8b1f2296c8b345b7"]]},{"id":"8b1f2296c8b345b7","type":"debug","z":"bdd7be38.d3b55","name":"debug 106","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":630,"y":3280,"wires":[]}]

What did you need a Switch node for?

1 Like
8

I think using a state machine would be an overkill since you are just incrementing or decrementing by unity.

9

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