uint8_t flag3;          //button's flag
const uint16_t p = 300;     //delay eliminates button rattling
uint32_t t;                 //time of button's counter
const uint8_t btm = A1;     // button's pin
bool btmStatus;
const uint8_t signPin =13;      // indicator of testing start and correct test

float r2 = 100;                 //resistance of current's shunt in ohms
uint16_t i_test = 12;            //test current in mA
uint16_t u_op;                       //reference voltage in mV
uint8_t pwmVal;                   //value PWM apropriate reference voltage
const uint8_t pwmPin = 9;        //pin numbers
const uint8_t akkum_pin = A4;     //controls akkum voltage
const uint8_t u_r2_pin = A5;      //controls current's shunt voltage
const uint16_t akkumVmin = 3000;    // in mV
const uint16_t tContAkk = 30000;   // period of monitoring akkum voltage (ms)
const uint32_t tContr = 30000;   // period of monitoring voltage controlling points (ms)
const uint8_t pwmToV  = 51;     // pwm to one volt

uint16_t volt;                  // voltage on monitoring pin in mV
bool flag = 1;            // flag test's finish
bool flag2 =1;            //flag correct test
uint8_t voltTol = 50;         // Tolerance of shunt's voltage in mV

const uint8_t stcp = 4;   //The pins connected to  74HC595
const uint8_t shcp = 7;
const uint8_t ds = 8;
const uint8_t numbs[] = {
  0b11000000, 0b11111001, 0b10100100, 0b10110000,
  0b10011001, 0b10010010, 0b10000010,                        //The codes DEC numbers
  0b11111000, 0b10000000, 0b10010000                  
};  


void setup() {
  // put your setup code here, to run once:
  pinMode(stcp, OUTPUT);
  pinMode(shcp, OUTPUT);
  pinMode(ds, OUTPUT);
  pinMode(pwmPin, OUTPUT);
  pinMode(akkum_pin, INPUT);
  pinMode(u_r2_pin, INPUT);
  pinMode(btm, INPUT_PULLUP);
  pinMode(signPin, OUTPUT); 
  
  u_op = i_test * r2;                         //calculate reference voltage
  pwmVal = pwmToV  * (long)u_op / 1000;       
  analogWrite(pwmPin,pwmVal);
  digitalWrite(signPin, LOW);           // indicator of testing start
  
}
void loop() {
  // put your main code here, to run repeatedly:
  static uint16_t testDur = 0;
  static uint16_t *modeInd = &testDur;        //the mode displaing of information on indicator
  
  uint16_t akkum_v;
  static uint32_t timer_akkum = millis();                //check akkum voltage
  if (millis() - timer_akkum > tContAkk){
    akkum_v = readVoltage(akkum_pin);
    timer_akkum = millis();
    if(akkum_v < akkumVmin){
      analogWrite(pwmPin,0);
    digitalWrite(signPin, HIGH);
      flag = 0;
    }
  }
  
  static uint16_t dispPeriod = 1000;    // pirod of voltage monitoring 
  static uint32_t timeDisp = 0;
  
  // check shunt voltage value 
  if(millis() - timeDisp > dispPeriod){
    timeDisp = millis();
    volt = readVoltage(u_r2_pin);    
  }
  if((volt < (u_op - voltTol)| volt > (u_op + voltTol)) && millis() > 30000){
    flag2 = 0;
  } 
  if(!flag2 && flag){
    digitalWrite(signPin, (millis() / 500) % 2);     // a led blinks  if shunt voltage is incorrect
  }
  
    //checking button push and change mode displaing information
    if(millis() - t > p){
    btmStatus = digitalRead(btm);
    if(flag3 == 0 && !btmStatus){
    t = millis();
    flag3 = 1;
    }
    
    if(flag3 > 0 && !btmStatus && (millis() - t) > (p + 500)){
      modeInd = (modeInd == &testDur) ? &volt: &testDur;
      t = millis();
      flag3 += 2;
    }
    else if(flag3 ==1 && btmStatus && millis() - t > p) {
      modeInd = (modeInd == &testDur) ? &akkum_v: &testDur;
    }
    
    if(flag3 > 0 && btmStatus){
      t = millis();
      flag3 = 0;
    }
  }
  

// calls function displaying of indicator
  static uint32_t cTime = 0; 
  static uint8_t dur1num = 2;      // Duration of displaying one digit in dynamic indication
  

  if(millis() - cTime > dur1num){
    if(flag) testDur = millis() / 60000;
    
    cTime = millis();
    display4_7Ind(*modeInd);
  } 
}

void display4_7Ind(uint16_t val)    //function displaying of indicator
{
                       //  convert voltage value to 4-digit 7-segment display
    uint8_t values[4];                   
    values[0] = val / 1000;
    values[1] = val % 1000 / 100;
    values[2] = val % 100 / 10;
    values[3] = val % 10;
  static int8_t digit = 3;            //setting first digit fou indication
  if (--digit < 0) digit = 3;         
  static uint16_t currNumber;
  currNumber = (numbs[values[digit]] << 8) | (1 << digit);  //splicing a DEC numbers bit and digit's bit
  // trasmiting 16 bits to 74HC595
  uint8_t i = 16;  
  while(i > 0){
    i--;
    uint8_t tt = bitRead(currNumber, i);
    PORTB |= tt;
    PORTD |= (1 << 7);
    PORTD &= ~(1 << 7);
    PORTB &= 0b11111110;
  }
  PORTD |= (1 << 4);
  PORTD &= ~(1 << 4);
}

uint16_t readVoltage(uint8_t pinN)
{
  uint16_t av_V = 0;
  for(int8_t i = 0; i < 4; ++i){
    
    uint16_t v = analogRead(pinN) * 5000L / 1024;
    av_V += v;
  }
  av_V /= 4;
  return av_V;
}