Build your own Adjustable Electronic DC Load using Arduino

#include <SPI.h>
#include <LiquidCrystal.h>
#define SS_PIN 10
#define MAX_VOLT 5.0
#define load_resistor 0.1
#define opamp_gain 6
#define average 10
const int slaveSelectPin = 10;
int number = 0;
int increase = A2;
int decrease = A3;
int current_sense = A0;
int voltage_sense = A1;
int state1 = 0;
int state2 = 0;
int Set = 0;
float volt = 0;
float load_current = 0.0;
float load_voltage = 0.0;
float current = 0.0;
float voltage = 0.0;
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
void setup() {
  // set the slaveSelectPin as an output:
  pinMode(slaveSelectPin, OUTPUT);
  pinMode(increase, INPUT);  // declare LED as output
  pinMode(decrease, INPUT);    // declare pushbutton as input
  pinMode(current_sense, INPUT);  // 
  pinMode(voltage_sense, INPUT);    // 
  // initialize SPI:
  SPI.begin();
  //set up the LCD's number of columns and rows:
    lcd.begin(16, 2);
  // Print a message to the LCD.
    lcd.print("Digital Load");
    lcd.setCursor(0, 1);
    lcd.print("Circuit Digest");
    delay (2000); 
}
void convert_DAC(unsigned int value)
{
   /*Step Size = 2^n, Therefore 12bit 2^12 = 4096
     For 5V reference, the step will be 5/4095 = 0.0012210012210012V or 1mV (approx)*/
  unsigned int container ;
  unsigned int MSB;
  unsigned int LSB;
  /*Step: 1, stored the 12 bit data into the container
   Suppose the data is 4095, in binary 1111 1111 1111*/
  container = value;    
  /*Step: 2 Creating Dummy 8 bit. So, by dividing 256, upper 4 bits are captured in LSB
   LSB = 0000 1111*/
  LSB = container/256;
  /*Step: 3 Sending the configuration with punching the 4 bit data. 
   LSB = 0011 0000 OR 0000 1111. Result is 0011 1111 */
  LSB = (0x30) | LSB;
  /*Step:4 Container still has the 21bit value. Extracting the lower 8 bits.
   1111 1111 AND 1111 1111 1111. Result is 1111 1111 which is MSB*/  
  MSB = 0xFF & container;    
 /*Step:4 Sending the 16bits data by dividing into two bytes. */
    digitalWrite(slaveSelectPin, LOW);
    delay(100);      
    SPI.transfer(LSB);
    SPI.transfer(MSB);    
    delay(100);
    // take the SS pin high to de-select the chip:
    digitalWrite(slaveSelectPin, HIGH);             
}
float read_current (void){
          load_current = 0;          
          for (int a = 0; a < average; a++){
          load_current = load_current + analogRead(current_sense);                
        }
        load_current = load_current / average;
        load_current = (load_current* MAX_VOLT) / 1024;
        load_current = (load_current / opamp_gain) / load_resistor; 
        return load_current;
}
float read_voltage (void){
          load_voltage = 0;          
          for (int a = 0; a < average; a++){
          load_voltage = load_voltage + analogRead(voltage_sense);                
        }
        load_voltage = load_voltage / average;
        load_voltage = ((load_voltage * MAX_VOLT)/1024.0)*6;
        return load_voltage;
}
void loop () {
        state1 = analogRead(increase);
        if (state1 > 500){
          delay(50);
           state1 = analogRead(increase);
           if (state1 > 500){
              volt = volt+0.02;
           }                    
        }
         state2 = analogRead(decrease);
        if (state2 > 500){
          delay(50);
           state2 = analogRead(decrease);
           if (state2 > 500){
              if (volt == 0){
                volt = 0;
              }
            else{
                volt = volt-0.02;
            }              
           }
        }
        number = volt / 0.0012210012210012;
        convert_DAC (number);        
        voltage = read_voltage();
        current = read_current();       
         lcd.setCursor(0, 0);
         lcd.print("Set Value");      
        lcd.print("=");
        Set = (volt/2)*10000; 
        lcd.print(Set);       
        lcd.print("mA    ");
        lcd.setCursor(0, 1);        
        lcd.print("I");      
        lcd.print("="); 
        lcd.print(current);       
        lcd.print("A ");
        lcd.print(" V");  
        lcd.print("=");
        lcd.print(voltage);       
        lcd.print("V");               
       // lcd.print(load_voltage);
        //lcd.print("mA    ");
       // delay(1000);
        //lcd.clear();
}