INTERFACING OF MICRO-CONTROLLER 8051 TO ADC (ADC 0804)

 INTERFACING OF MICRO-CONTROLLER 8051 TO ADC (ADC 0804)

Micro-controller 8051 does not has in-built ADC. So, we are using external ADC 0804. It is an 8-bit ADC so, resolution = 8-bit.

ADC 0804 Pin Details:

                            

DB7 - DB0 – Are 8 Data Pin which hold Converted Digital data.

CS - It is an Active low signal usually we can ground it, or use a pin from microcontroller to control it by passing high to low pulse in the pin.

RD – It is an Active low signal it use to read data from ADC0804 Data line (DB7-DB0).

WR - It is an Active low signal. When low to high signal is passed in that pin the adc conversion start.

INTR - It is an Active low signal. It is used to Check for End of Conversion.

Vref/2 – It is the References voltage is given to ADC for Step sizes Calculation of conversion.

AGND – Analog Ground.

DGND – Digital Ground.

Important Note:

Resolution of this ADC is 8bit, so that means the Steps ranges from (0-255)

Formula:

            Step sizes = Vref/(2ⁿ -1);              n = 8(Resolution of ADC).

                            = Vref/(256 - 1);

                                   =  Vref/255;  

• To convert and display the data into LCD we use a formula to convert it to ascii.

                                      if data = 125  

     for unit place data the formula is

•         (data%10) = 5 => now or with 30h we get ascii value i.e.( 5|0x30 ) = 35

                               35 in ascii means 5 numeric.

     for tenth place data the formula is

•          ((data/10)%10) = 2 => now or with 30h we get ascii value i.e.( 2|0x30 ) = 32

                               32 in ascii means 2 numeric.

     for send data the formula is

•        ((data/100)%10) = 1 => now or with 30h we get ascii value i.e.( 1|0x30 ) = 31

                               31 in ascii means 1 numeric.

• To convert the data into LCD in Hex format using lookup table
•  first Mask the low bits using 0xF0 and shift higher 4bit data to lower 4 bit and        get the equal data from lookup table.
•  then, mask the Higher bits using 0x0F and compare it with lookup table and          display it.

                 Ex:

              Higher bits = (data & 0xF0)>>4;

              Lower bits = (data & 0x0F);

• To Convert the Digital data to analog we have formula ie;

                       

                        D_out = V_in/step sizes;

                        So, when we alter it we get

                        V_in = D_{out *} Step size;

                        V_in = D_out * (Vref/2ⁿ-1);

Apply this formula we get input voltage;

Thus we have done the Coding for Interfacing of ADC to 8051. 


Program for ADC:click for code

Video on above Example: Click for videos