aLec22_ADC - Introduction to Embedded Microcomputer Systems...

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Introduction to Embedded Microcomputer Systems Lecture 22.1 Jonathan W. Valvano Recap Output compare interrupts Metrowerks Codewarrior Overview Analog to Digital Convertor Transducer: mechanical, electrical Using output compare interrupts to establish sampling Range(volts) = Precision(alternatives) • Resolution(volts) Time (s) 0 4 8 12 16 20 24 28 32 01234567891 0 Continuous analog signal Discrete digital signal Figure 11.1. An analog signal is represented in the digital domain as discrete samples. 10-bit Analog to digital Converter Analog input 0 V in +5 Digital output 0 ATD0DR0 1023 Digital Output is about 1024*V in /5 or Digital Output is about 1023*V in /5 Analog signal (volts) 0 32 64 96 128 160 192 224 256 01234 5 zoomed in ADC Digital Outputs Analog Input DAC Digital Input Analog Output Analog signal (volts) 0 128 256 384 512 640 768 896 1024 5 zoomed in ADC Digital Outputs Analog Input DAC Digital Input Analog Output Figure 11.2. Input/output functions of a DAC and an ADC. 8-bit Analog to digital Converter Analog input 0 V in +5 Digital output 0 ATD0DR0 255 Digital Output is about 256*V in /5
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Introduction to Embedded Microcomputer Systems Lecture 22.2 Jonathan W. Valvano or Digital Output is about 255*V in /5 Find the 16 analog inputs on the 9S12DG128 Figure 4.18. Block diagram of a Freescale 9S12DP512. 9S12DG128 has less RAM/ROM and CAN ports ATD0CTL2=$80; set bit 7 to enable ADC ATD0CTL3=$08; sequence length=1 ATD0CTL4 bit 7=0 for 10-bit, =1 for 8-bit ADC Bits 4-0 internal clock (how fast the ADC runs) Let m be the bottom 5 bits of ATD0CTL4
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This note was uploaded on 03/28/2011 for the course EE 16345 taught by Professor Yerraballi during the Spring '11 term at University of Texas at Austin.

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aLec22_ADC - Introduction to Embedded Microcomputer Systems...

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