Analog to Digital Conversion

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Analog to Digital Conversion

• Abbreviated A/D, ADC
• Common peripheral on microcontrollers
• Very common need for embedded systems
• Goal
• Convert analog signals
• continuous time
• continuous amplitude
• to digital signals
• discrete time
• discrete amplitude
• Must interpolate

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Parallel Interface
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Serial Interface
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Digital to Analog

• DAC or D/A
• Convert a digital value to a voltage
• Not supported by HC11 directly
• External devices

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DAC Techniques

• Pulse-width modulation similar to what you have
  been doing to control motor speed
• Summing Amplifier (binary weighted) sum current
  from various resistors
• R2R Ladder form of summing amplifier
• Segmented a resistor for each DAC value

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Summing Amplifier
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R2R
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Parallel DAC
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Serial DAC
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Lab Tomorrow

• Demo LCD
• Install line tracker

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Line Tracker

• Three digital outputs
• One for each sensor
• Where should we connect?
• What will our implementation be?
• ISR?
• Task?

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