I don't understand how this all works

[bko]

Hi @Bobzilla

The sample code does indeed work fine, you just didn't cut and paste all of it. Not a big deal. The relays are defined at the top of the sample:

int RELAY1 = D3;
int RELAY2 = D4;
int RELAY3 = D5;
int RELAY4 = D6;

An "exposed function" is something you declare using Particle.function(). It is a way of letting you use the Particle cloud to call a function remotely on your Photon or Electron. A Particle function always takes a String argument and returns and int that generally indicates success or failure of the call, but you can decide what it means.

Here is a link to a tutorial I wrote a long time ago using both functions and variables. Note that Spark.function is now Particle.function and a few other small changes.

Tutorial: Spark Variable and Function on One Web Page

Let’s say you have a Spark core with both a Spark variable and a Spark function. In my case, I have the world’s simplest servo control sketch, using the nice miniature servo in the Spark Maker Kit. Using these parts, we will build a servo that you can control from a web page anywhere and monitor the position of the servo too! Here’s a preview of the finished tutorial: [image] There is a coarse adjust slider, two fine adjust buttons, and the current position of the servo is displayed. That…

You will see that you don't need your own webserver to use any of this--any modern browser will work. If you do have a webserver, that can let you do more advanced things, but it is not required.