int pin                 = 5;     //      D7 D7 D7
const int MIDDLE        = pin++; //    D6         D8
const int TOP_LEFT      = pin++; //    D6         D8
const int TOP           = pin++; //    D6         D8
const int TOP_RIGHT     = pin++; //       D5 D5 D5
const int BOTTOM_LEFT   = pin++; //    D9         D11
const int BOTTOM        = pin++; //    D9         D11
const int BOTTOM_RIGHT  = pin++; //    D9         D11
const int DOT           = pin++; //     D10 D10 D10    D12


void setup() {
  int pin = MIDDLE;
  pinMode( pin++, OUTPUT );
  pinMode( pin++, OUTPUT );
  pinMode( pin++, OUTPUT );
  pinMode( pin++, OUTPUT );
  pinMode( pin++, OUTPUT );
  pinMode( pin++, OUTPUT );
  pinMode( pin++, OUTPUT );
  pinMode( pin++, OUTPUT );

  // ground pins
  pinMode( A0, OUTPUT ); // 10s digit
  pinMode( A1, OUTPUT ); // 1s digit 

}


void loop() {
  
  int dwell = 100; // max 100ms avoids flicker on wokwi

  select10s(); // apply ground to unit 0
  draw2();
  delay( dwell );

  select1s(); // apply ground to unit 1
  draw3();
  delay( dwell );
}

// connect the ground circuit for only unit 1 - disabling unit 0
void select1s() {
  blank();
  digitalWrite( A0, HIGH ); // turn off unit 0
  digitalWrite( A1, LOW );  // turn on unit 1
}

// connect the ground circuit for only unit 0 - disabling unit 1
void select10s() {
  blank();
  digitalWrite( A1, HIGH ); // turn off unit 1
  digitalWrite( A0, LOW );  // turn on unit 0
}

// cut power to all eight segments of all displays
void blank() {
  pin = MIDDLE;
  digitalWrite( pin, LOW );
  digitalWrite( ++pin, LOW );
  digitalWrite( ++pin, LOW );
  digitalWrite( ++pin, LOW );
  digitalWrite( ++pin, LOW );
  digitalWrite( ++pin, LOW );
  digitalWrite( ++pin, LOW );
  digitalWrite( ++pin, LOW );
}

// draw a 0 figure in the active display(s)
void draw0() {
  digitalWrite( MIDDLE,       LOW );
  digitalWrite( TOP_LEFT,     HIGH );
  digitalWrite( TOP,          HIGH );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  HIGH );
  digitalWrite( BOTTOM,       HIGH );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}

// draw a right-justified 1 figure in the active display(s)
void draw1() {
  digitalWrite( MIDDLE,       LOW );
  digitalWrite( TOP_LEFT,     LOW );
  digitalWrite( TOP,          LOW );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  LOW );
  digitalWrite( BOTTOM,       LOW );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}

// draw a 2 figure in the active display(s)
void draw2() {
  digitalWrite( MIDDLE,       HIGH );
  digitalWrite( TOP_LEFT,     LOW );
  digitalWrite( TOP,          HIGH );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  HIGH );
  digitalWrite( BOTTOM,       HIGH );
  digitalWrite( BOTTOM_RIGHT, LOW );
  digitalWrite( DOT,          LOW );
}

// draw a 3 figure in the active display(s)
void draw3() {
  digitalWrite( MIDDLE,       HIGH );
  digitalWrite( TOP_LEFT,     LOW );
  digitalWrite( TOP,          HIGH );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  LOW );
  digitalWrite( BOTTOM,       HIGH );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}

// draw a 4 figure in the active display(s)
void draw4() {
  digitalWrite( MIDDLE,       HIGH );
  digitalWrite( TOP_LEFT,     HIGH );
  digitalWrite( TOP,          LOW );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  LOW );
  digitalWrite( BOTTOM,       LOW );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}

// draw a 5 figure in the active display(s)
void draw5() {
  digitalWrite( MIDDLE,       HIGH );
  digitalWrite( TOP_LEFT,     HIGH );
  digitalWrite( TOP,          HIGH );
  digitalWrite( TOP_RIGHT,    LOW );
  digitalWrite( BOTTOM_LEFT,  LOW );
  digitalWrite( BOTTOM,       HIGH );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}

// draw a 6 figure in the active display(s)
void draw6() {
  digitalWrite( MIDDLE,       HIGH );
  digitalWrite( TOP_LEFT,     LOW );
  digitalWrite( TOP,          HIGH );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  HIGH );
  digitalWrite( BOTTOM,       HIGH );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}

// draw a 7 figure in the active display(s)
void draw7() {
  digitalWrite( MIDDLE,       LOW );
  digitalWrite( TOP_LEFT,     LOW );
  digitalWrite( TOP,          HIGH );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  LOW );
  digitalWrite( BOTTOM,       LOW );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}

// draw an 8 figure in the active display(s)
void draw8() {
  digitalWrite( TOP_LEFT, HIGH );
  digitalWrite( TOP, HIGH );
  digitalWrite( TOP_RIGHT, HIGH );
  digitalWrite( MIDDLE, HIGH );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( BOTTOM, HIGH );
  digitalWrite( BOTTOM_LEFT, HIGH );

  digitalWrite( MIDDLE,       HIGH );
  digitalWrite( TOP_LEFT,     HIGH );
  digitalWrite( TOP,          HIGH );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  HIGH );
  digitalWrite( BOTTOM,       HIGH );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}

// draw a 9 figure in the active display(s)
void draw9() {
  digitalWrite( MIDDLE,       HIGH );
  digitalWrite( TOP_LEFT,     HIGH );
  digitalWrite( TOP,          HIGH );
  digitalWrite( TOP_RIGHT,    HIGH );
  digitalWrite( BOTTOM_LEFT,  LOW );
  digitalWrite( BOTTOM,       HIGH );
  digitalWrite( BOTTOM_RIGHT, HIGH );
  digitalWrite( DOT,          LOW );
}