 Welcome to all of you. Myself Ravindra Chauhan from Department of Electronics Engineering, Walsh Chandrista of Technology, Swalapur. Today we will discuss how to interface the ADC with the microcontroller 8051. Now after discussion, you will be able to apply the concept of this ADC interfacing in any controller based system design. Now the flow of our discussion will be like this. First we will see the signals of ADC 08008. Then we will discuss how to interface this ADC with the microcontroller 8051. And then we will see how to write the program for analog to digital conversion by using the ADC. Now we will see ADC 08008 signals. Now ADC 08008 is called the 8-bit ADC because it is producing the 8-bit digital output on the pin D0 to D7. Now Ion 0 to Ion 7, these are the 8 analog input channels through which one can apply the analog signal to the ADC. Now to select one of these 8 analog channels, 3 channel select lines are provided that is CHS0 to CHS2. Using these 3 channel select lines, one can select the appropriate analog input channels. Next pin is called the ALE address latch enable. This latch enable signal is used to latch the address of the selected analog input channel. There is need to send the high pulse on the ALE. Means ALE is the input signal to the ADC. To the program there is need to generate the high pulse on the ALE pin of the ADC. Now once the input is applied, channel is selected, then next step is to start the conversion. So there is need to send the command start of conversion to the ADC. Now this start of conversion is again the input to the ADC and ADC required high pulse to start the conversion. After receiving the start of conversion signal, ADC will start the conversion of analog input to the digital one and when it completes the conversion, ADC is generating one output called the end of conversion. This output is a low pulse type signal. So to check whether the conversion is completed or not, there is need to monitor the status of the EOC signal. When we find EOC low, then it indicates that the conversion is completed. Once the conversion is completed, the next step is to read the digital output produced by the ADC. Now to read the digital output, which is available on D0 to D7, for that there is need to send the signal called output enable signal. Now this is high type signal. Now this signal is required to enable the data pins D0 to D7, V reference plus and V reference minus these two are called the reference voltages. Is for example, if V reference plus is connected to plus 5 volt and V reference minus is connected to the ground, then for the 0 volt input, the ADC will produce the 00 as output and for plus 5 volt, the ADC will produce the FF as a digital output. VCC and ground are the required power supply pins of the ADC and clock is the input signal required for the ADC and in synchronization with this clock, all the internal operations will take place. Now as we have seen, there are eight analog input channels from Ion 0 to Ion 7 and their addresses are shown like this. If all these three channel select lines are 00, so input channel 0 will get selected. For 001, the input channel 1 will get selected and if all these three lines are 111, then the input channel 7 will get selected. Now on ALE it required high pulse to latch the address of the input channel. To start the conversion, there is need to send the high pulse on SOC. After conversion, ADC will generate the low pulse on EOC. Then there is need to send high pulse on OEPIN to enable the digital output pins. Next we will see how to interface the ADC to the 8051 microcontroller. So you can use any available ports of the 8051. Here we have used port 1 for the digital output from the ADC. That's why here it is shown P1.0 to P1.7 means port 1 is connected to the D0 to D7 pins of the ADC. Now to select one of the input channel, the pins from the port 2 are used. So P2.0 to P2.2 is connected to the three channel select pins of the ADC. Similarly, the P2.4 from the 8051 is connected to the ALE pin, P2.5 is connected to the start of conversion pin of ADC. Since to start the conversion, there is need to send the high pulse on P2.5. After conversion, the ADC will send the EOC signal which we can read through the P2.6. And to enable the digital outputs, there is need to send the high pulse on OE. So P2.7 is connected to the OE pin of ADC. V reference plus is connected to the plus 5-hole, V reference minus is connected to the ground. So that our input voltage will vary from 0 to plus 5-hole. Means for input 0-hole, the digital output will be 00H. And for plus 5-hole, the digital output should be FFH. Now next is how will you write the program for the ADC conversion. So for that, first we have to decide which input channel should be used. So this ADC is having 8 analog input channels. So physically there is need to connect the analog input to one of these input channels. Once this physical connection is happens, then through the program you have to write the instruction to select the particular input channel. So there is need to send the respective address on channel select lines. Next step is output the high pulse on P2.4 to send the ELE signal to ADC. Now you just think how to generate the high pulse. Pause the video and write your answer. The answer of this question is to send the high pulse on P2.4, first set the P2.4 pin. Then call a delay of few microseconds and reset the pin P2.4. So then next step is output the high pulse on P2.5 to send the SOC signal to ADC. Wait for low pulse on P2.6 for EOC signal. Now to read the digital output make P2.7 high. Next read the digital output on port 1 and repeat the steps 3 to 7 for the next conversion. Now take the assignment like this, write a program to convert analog voltage to digital value, references used are microcontroller by Ajay Deshmukh and 8051 and embedded C programming by Majidi and Majidi. Thank you.