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    Interfacing - ADC & DAC: ADC (Analog To Digital Converter)

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    Jagan V
    This document discusses interfacing an 8-bit analog-to-digital converter (ADC 0804) and digital-to-analog converter (DAC 0808) with an 8051 microcontroller. It describes how the ADC works and the steps to read an analog input value and convert it to digital. It also explains how the DAC converts a digital value to an analog output using R/2R ladder method. Circuit diagrams are provided to show how the ADC and DAC are connected to the microcontroller and other components to convert between analog and digital signals.

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    Interfacing - ADC & DAC: ADC (Analog To Digital Converter)

    Uploaded by

    Jagan V
    15 views8 pages
    This document discusses interfacing an 8-bit analog-to-digital converter (ADC 0804) and digital-to-analog converter (DAC 0808) with an 8051 microcontroller. It describes how the ADC works and the steps to read an analog input value and convert it to digital. It also explains how the DAC converts a digital value to an analog output using R/2R ladder method. Circuit diagrams are provided to show how the ADC and DAC are connected to the microcontroller and other components to convert between analog and digital signals.

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    1585982511

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    This document discusses interfacing an 8-bit analog-to-digital converter (ADC 0804) and digital-to-analog converter (DAC 0808) with an 8051 microcontroller. It describes how the ADC works and the steps to read an analog input value and convert it to digital. It also explains how the DAC converts a digital value to an analog output using R/2R ladder method. Circuit diagrams are provided to show how the ADC and DAC are connected to the microcontroller and other components to convert between analog and digital signals.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    15 views8 pages

    Interfacing - ADC & DAC: ADC (Analog To Digital Converter)

    Uploaded by

    Jagan V
    This document discusses interfacing an 8-bit analog-to-digital converter (ADC 0804) and digital-to-analog converter (DAC 0808) with an 8051 microcontroller. It describes how the ADC works and the steps to read an analog input value and convert it to digital. It also explains how the DAC converts a digital value to an analog output using R/2R ladder method. Circuit diagrams are provided to show how the ADC and DAC are connected to the microcontroller and other components to convert between analog and digital signals.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 8

    Interfacing - ADC & DAC

    ADC (Analog to digital converter)


    ➢ forms a very essential part in many embedded projects and this article is
    about interfacing an ADC to 8051 embedded controller.
    ➢ ADC 0804 is the ADC used here and before going through the
    interfacing procedure, we must neatly understand how the ADC 0804
    works.
    ➢ ADC0804 is an 8 bit successive approximation analogue to digital
    converter from National semiconductors.
    ➢ The features of ADC0804 are differential analogue voltage inputs, 0-5V
    input voltage range, no zero adjustment, built in clock generator, reference
    voltage can be externally adjusted to convert smaller analogue voltage
    span to 8 bit resolution et

    16EC242 - Microprocessor and Microcontroller Dr.B.Sivasankari/ASP/ECE 1


    Interfacing - ADC & DAC

    Pin diagram of ADC


    ➢ The voltage at Vref/2 (pin9) of ADC0804 can be externally adjusted to convert
    smaller input voltage spans to full 8 bit resolution. Vref/2 (pin9) left open means
    input voltage span is 0-5V and step size is 5/255=19.6V.

    16EC242 - Microprocessor and Microcontroller Dr.B.Sivasankari/ASP/ECE 2


    Interfacing - ADC

    Interfacing – ADC with 8051


    Steps for converting the analogue input and reading the output from ADC0804.
    ➢ Make CS=0 and send a low to high pulse to WR pin to start the conversion.
    ➢ Now keep checking the INTR pin. INTR will be 1 if conversion is not finished and
    INTR will be 0 if conversion is finished.
    ➢ If conversion is not finished (INTR=1) , poll until it is finished.
    ➢ If conversion is finished (INTR=0), go to the next step.
    ➢ Make CS=0 and send a high to low pulse to RD pin to read the data from the ADC.

    16EC242 - Microprocessor and Microcontroller Dr.B.Sivasankari/ASP/ECE 3


    Interfacing – ADC (circuit Diagram)

    16EC242 - Microprocessor and Microcontroller Dr.B.Sivasankari/ASP/ECE 4


    Interfacing - ADC (circuit operation)

    ➢ The circuit initiates the ADC to convert a given analogue input , then accepts the
    corresponding digital data and displays it on the LED array connected at P0.
    ➢ Eg. if the analogue input voltage Vin is 5V then all LEDs will glow indicating
    11111111 in binary which is the equivalent of 255 in decimal.
    ➢ AT89s51 is the microcontroller used here. Data out pins (D0 to D7) of the
    ADC0804 are connected to the port pins P1.0 to P1.7 respectively.
    ➢ LEDs D1 to D8 are connected to the port pins P0.0 to P0.7 respectively. Resistors
    R1 to R8 are current limiting resistors.
    ➢ In simple words P1 of the microcontroller is the input port and P0 is the output
    port. Control signals for the ADC (INTR, WR, RD and CS) are available at port pins
    P3.4 to P3.7 respectively.

    16EC242 - Microprocessor and Microcontroller Dr.B.Sivasankari/ASP/ECE


    Interfacing - ADC (circuit operation)

    ➢ Resistor R9 and capacitor C1 are associated with the internal clock circuitry of the
    ADC. Preset resistor R10 forms a voltage divider which can be used to apply a
    particular input analogue voltage to the ADC.
    ➢ Push button S1, resistor R11 and capacitor C4 forms a debouncing reset
    mechanism.
    ➢ Crystal X1 and capacitors C2,C3 are associated with the clock circuitry of the
    microcontroller.

    16EC242 - Microprocessor and Microcontroller Dr.B.Sivasankari/ASP/ECE 6


    Interfacing - DAC with 8051

    ➢ Digital to Analog converter (DAC)


    ➢ is a device, that is widely used for converting digital pulses to analog signals. There
    are two methods of converting digital signals to analog signals.
    ➢ These two methods are binary weighted method and R/2R ladder method. In this
    article we will use the MC1408 (DAC0808) Digital to Analog Converter.
    ➢ This chip uses R/2R ladder method. This method can achieve a much higher
    degree of precision. DACs are judged by its resolution.
    ➢ The resolution is a function of the number of binary inputs. The most common
    input counts are 8, 10, 12 etc.
    ➢ Number of data inputs decides the resolution of DAC. So if there are n digital input
    pin, there are 2n analog levels. So 8 input DAC has 256 discrete voltage levels

    16EC242 - Microprocessor and Microcontroller Dr.B.Sivasankari/ASP/ECE 7


    Interfacing - DAC with 8051(circuit diagram)

    16EC242 - Microprocessor and Microcontroller Dr.B.Sivasankari/ASP/ECE 8

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