1) Master Microcontroller: The functionality of the WIU is
based on the microcontroller, which is programmed to perform
diverse tasks, as is shown in Fig. 7. The first task of the
program is to download from a web server the date and time
through the GPRS module. The WIU is ready to transmit
via XBee the date and time for each WSU once powered.
Then, the microcontroller receives the information package
transmitted by each WSU that conform the WSN.