RPi GPIO Input Inverting

[rlno...@gmail.com]

I am using the rpi gpio pins to monitor some normally closed switch contacts (doors). But with the door closed, a 1 is sent from the input pin.

My application requires the input to be inverted so a closed door sends 0 and open sends 1.

I have not been able to find an inverting node to do this. What is the proper code to use in a function node to do the same thing?

[Julian Knight]

I'm afraid most of us far too easily fall back on function nodes and I'm sure there are other way. But a really simple way would be to use a function node with the following code - assuming your data is on the payload and can only be a numeric 0 or 1:

msg.payload = ! msg.payload;
return msg;

Check if it comes out as text though, in which case you may have to force it back to a number. Also make sure it can't be anything other than 0 or 1, if it can, you need to do additional error checks.

[rlno...@gmail.com]

Yes that works but it is in text.  How do I "force" it back to a number? Noob here.

[Julian Knight]

No problem.

Try something like 

msg.payload = ! parsInt(msg.payload);
return msg;

https://www.w3schools.com/jsref

https://developer.mozilla.org/en-US/docs/Web/JavaScript

[Dave C-J]

That should be

   parseInt

With an e

   

--

Sent from phone.

[Colin Law]

I generally use Number(msg.payload) as that does its best to make
sense of anything you send to it. If it cannot make sense of it then
it returns NaN. Parseint will fail if you give it a number rather
than a string, I think. So I tend to sloppily stick in Number()
whenever I think there is any doubt about the format. Probably that is
reprehensible behaviour on my part.

Colin

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[rlno...@gmail.com]

I added the missing letter E but still get a true or false instead of 0 or 1.

[Dave C-J]

Ooops, maybe

   msg.payload = (msg.payload == 1) ? 0 : 1;

   return msg;

--

Sent from phone.

[rlno...@gmail.com]

Yup! That was it!  Thanks guys. One problem solved.  If there are more problems, I know where to find the experts.

Thanks again!

[Lasse Klein]

This works if you move the ! inside the paranthesis: 

msg.payload = Number(! msg.payload);