Specifications

 Design – This will be most important feature. In the beginning the

developer has to lay down the outline of how the design will flow. Which

ways would be simpler, reduce memory, CPU Utilization, etc. Should the

developer use flash memory, or another type of volatile memory. This

should be well thought out and planned before coding starts. This will

allow the code to be more efficient and proficient.

Within the software aspect of the design, the programmers should follow the

steps mentioned above in order to produce a concise, easily read, and highly

effective set of software routines. The MSP430 software will be written using a C

Language compiler provided by the microcontroller manufacturer. The MSP430

requires software routines customized for communications with different devices.

The devices that will interface with the MSP430 specifically shall use standard

communications and signaling protocols over the integrated hardware. Time

continuous voltage readings from sensors that act as system input will be

decoded by the integrated analog-to-digital converter, while input push buttons

will trigger microprocessor interrupts to be service by the software.

There are two different systems, one being the hand held unit and the other the

control box unit. The hand held unit should be able to take in input from the user,

and provide meaningful feedback in the form of visual and audio output. The

inputs that are connecting to the MSP430 are the alcohol sensor, the push

buttons, and the airflow detection sensor. The MSP430 will drive the output blood

alcohol calculations or status messages to the integrated display device. The

software design is illustrated in the diagram in Figure 2.6.1.1. When the a push

button is depressed, the software must be able to determine the current system

state and act accordingly. Depending on which button is pressed, and the

duration over which it is held, this will involve activating and priming the sensors

for accurately reading the user’s breath sample, preparing a message to be sent

to the control box unit for authentication, enabling or disabling the integrated

display unit, or turning off the hand held unit.