The document discusses interfacing an analog to digital converter (ADC) chip, specifically the 0804 and 0808 chips, with a microcontroller. It explains that the ADC converts an analog voltage to an 8-bit digital value representing voltages from 0 to 255. It provides the initialization and timing steps to start a conversion by writing to the chip and read the digital output by reading from the chip once conversion is complete.

1. Interfacing ADC

2. What is ADC? ADC – analog to digital conversion It converts the given analog value to a digital value There are lot of digital ICs available to convert analog to digital In microcontroller interfacing the frequently used ICs are 0804 and 0808

3. 0804 – an ADC

4. Interfacing ADC

5. Working of ADC For every interfacing initialization is needed, For ADC the initial values are INTR=1; // interrupt for completion of ADC process rd=1; // read from 0804 wr=1; // start conversion write..

6. Working of ADC contd. Next step is to start the process of converting analog voltage to digital data By changing the state of the write pin – a transition from 0 to 1 will start the conversion. End of conversion will be acknowledged by a change in the INTR state… See the timing diagram of the conversion starts

7. Timing diagram of START Conv.

8. Reading the data To read the data from 0804 the read pin state must be ‘0’. After reading the data read pin must be change back into ‘1’ The data obtained from the 0804 will be from ‘0’ to ‘255’ , since the ADC is a 8 bit adc and obtained value will be inbetween 2 0 to 2 8 .

9. Timing diagram of reading from 0804

10. Assignment Convert analog and display in LCD Find the room temperature and display the degree Celsius value in LCD.