Specifications

29
output rating. This component is not included in the following diagram, but will be
discussed in detail in the relays section of this paper.
Figure 8 shows the interfacing within the main control unit. It also specifies the
type of connection used and the number of wires required for each connection
type.
Main Control Unit Interfacing
Figure 8 Main Control Unit interfacing
The dsPIC33FJ256GP710A can connect to 2 UART, 2 I
2
C, and 2 SPI modules.
As the diagram shows, both the ZigBee and the 802.11b chips connect via SPI,
the SHT21 temperature and humidity sensor connects via I
2
C, and the 7”
Evervision LCD touch screen connects via Serial interface that will consume one
of the two UART connections. After considering all of the necessary
connections, we see that both of the I
2
C connections will be used, one of the two
SPI connections will be used, and one of the two UART connections will be used.
There will be one SPI and one UART connections left floating in the design of the
main control unit. The dsPIC33FJ256GP710A will be programmed in the C high
level language using the MPLAB C Compiler from MicroChip.