Page 120 - Programming the Photon Getting Started With the Internet of Things

Spark.function("led",ledToggle);

This is the code that sets up the function, giving it the name “led.” The second
parameter is the name of the function in the out program to run when the led function is
called over the Internet. Before we actually start turning the LED on or off, we need to

make sure that the LED is first in an off state, using the following command to write the
status to the LED:

digitalWrite(led1, LOW);

We keep the loop function part of the program empty because we have created a

separate function to catch the led command and we do not need to keep listening for it in
the loop function. When the ledToggle function is called as a result of receiving a
message from the Internet, it receives a string as a parameter. In the HTTP request that we

will send to the Photon board, we will make sure that we either turn the LED on or off
using the correct parameter. If the function received a value that is either on or off, it will
return 1 to indicate a successful command received. If the command sent is unsuccessful,
then it will return a value of −1, indicating it has failed the checking process.

Something to consider also is the security process of actually sending commands to the
Photon board. This is an important process, as you do not want your device open to
anyone on the Internet to start sending ghost commands to your Photon board. Certain
measures can take place when you send your commands to the Photon board. The Photon

board requires up to two tokens to help secure your device.

The first token is your device’s unique identifier—each of your devices will have this
unique token number to help identify your device, especially when you are using several
boards at the same time. You can find your device’s ID by checking your device in the

Particle build integrated development environment (IDE) and selecting your Particle
device, as shown in Figure 6.3.