Specifications

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Figure 3.1-2: Signal flow summary of the base/control unit. Small arrows indicate
flow into the microcontroller, and large arrows indicate output from the
microcontroller.
3.2 Microcontroller Interface
The microcontroller acts as the centerpiece for the entire system design process,
as its function is to receive and process all input data, then return a relevant
result both as a sensory output to the user and a relevant system message to its
counterpart in the opposing hardware unit. As such, there must be defined
specifications for how the microprocessor will communicate with all of these
system devices. The components selected for use in both the hand held unit
design as well as the automobile control box will utilize manufacturer provided
application programming interfaces and industry standard communication
protocols in order to exchange information.
3.2.1 Inter-Integrated Circuit (I²C)
Developed by NXP Semi, now known as Phillips, I²C is a two line serial
communications bus, designed for communications between multiple devices on
the same lines, using a master-slave configuration. This is based on that idea
that most systems have at least one central arbiter or controller, whose job is to
interpret and relay different system device communications between a multitude
of system “slave” devices. In our system design, the I²C bus is offered by the TI
MSP430 microcontroller as a standard for device communications, and as such