ChApTEr 2 ■ hArdwArE for IoT SoluTIonSThere is one drawback, and it depends on how you will use the shield. Like some of the Arduino
Ethernet shield clones (see the “A Warning About Ethernet Shield Variants” sidebar), it does not use the
Ethernet library. You must download a new library to use it (http://arduino.cc/en/Reference/WiFi101).
This may not be an issue if you have only a few nodes, but if you want to use the shield with existing sketches
or sketches written for the Ethernet library, you may need to make some modifications to get it to work.
Fortunately, the new library has many examples you can use to write your sketches. I have not used the
shield in my projects yet, but initial experimentation shows the new library is similar to the Ethernet library
and thus should not be difficult to use in place of an Arduino Ethernet shield.
Arduino WiFi Shield
The Arduino WiFi shield is the older version of the newest 101 shield. It supports only simple authentication
(no crypto features) but comes complete with a MicroSD card reader. What I like most about the shield is it
is 100 percent compatible with the Ethernet library, making it easy to use the same core code in sketches for
both the Arduino Ethernet and WiFi shields. There is a bit of a different startup code, but all your calls to the
Ethernet library and its classes remain unchanged. Figure 2-19 shows the Arduino Ethernet shield.
Figure 2-18. Arduino WiFi shield 101