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Microcontroller Programming and Interfacing Texas Instruments MSP430 by Daniel J. Pack, Steven F. Barrett

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241
CHAPTER 8
Analog Peripherals
Objectives: After reading this chapter, the reader should be able to
Describe the function of an analog-to-digital converter (ADC) and a digital-to-analog con-
verter (DAC)
Explain the methods used to perform conversions in the MSP430 microcontroller
Configure the MSP430 microcontroller to accept analog signals and convert them into digital
forms
Configure the MSP430 microcontroller to convert digital signals into appropriate analog
signals
Use interrupts associated with the MSP430 microcontroller’s ADC and DAC systems
Interface the MSP430 microcontroller with compatible Texas Instruments analog devices
A microcontroller would have limited capability if it was not able to interact with its environ-
ment. In this chapter, we discuss the subsystems that allow the microcontroller to input and output
analog signals, typically needed to interact with the environment. In Chapter A.5, we presented the
input and output interfaces of MSP430 microcontroller, concentrating on the digital interface. In
this chapter, we introduce the MSP430’s analog-to-digital converter (ADC) and digital-to-analog
converter (DAC) systems.
The importance of the two converter systems are clear as the controller must work with analog
signals of the world in which we live. Consider a simple example of your voice signal. To process,
store,and transmit a voice signal using a digital system, such as the MSP430 controller, a system must
have a means to convert analog signals to their equivalent digital forms and also to convert back to
a useful analog forms. The analog-to-digital converter and the digital-to-analog converter perform
these required tasks. With both the digital and analog interfaces, the MSP430 microcontroller truly
reflects its name as a Mixed Signal Processor (MSP).
8.1 MOTIVAT ION
We live in an analog world. That means when we represent physical phenomena as signals over
time, the signal can take any of the infinite number of values at each time. For example, take the
case of your voice. If we display your voice over time, it will be a continuous signal whose pitch

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