Increase or decrease const byte value inside the code with a push button

Question

I'm kind of new in the Arduino world. I decided to make a self learning project with an Arduino where it controls a conveyor that simply moves from right to left and back again. There is a start and stop button. On each end of the conveyor are inductive sensors to stop the motor when it reaches the end position. After a delay, the conveyer starts again the opposite direction. Inside the code I have a cycle counter that stops the conveyer after a certain number of cycles. Now my question is, how could I change the value of the cycle counter using two push buttons. One to increase the other to decrease.

If there is somebody who could help I would appreciate. Thanks already

const byte sensorLinksEnd  =  2;
const byte sensorRechtsEnd =  3;
const byte startPin        =  4;
const byte stopPin         =  5;
const byte relaisLinks     =  6;
const byte relaisRechts    =  7;

enum {relaisAn, relaisAus};
enum {warten, on, rechts, haltrechts, links, haltlinks, off};
byte schritt = warten;
byte zyklus = 20; //cycles
const byte maxzyklus = 20; //max cycles

void setup() {
  Serial.begin(115200);
  Serial.println(F("Start...."));
  pinMode(sensorLinksEnd, INPUT);
  pinMode(sensorRechtsEnd, INPUT);
  pinMode(startPin, INPUT);
  pinMode(stopPin,  INPUT);
  pinMode(relaisLinks, OUTPUT);
  digitalWrite(relaisLinks, relaisAus);
  pinMode(relaisRechts, OUTPUT);
  digitalWrite(relaisRechts, relaisAus);
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);
}

void loop() {
  schrittkette();
}

void schrittkette()
{
  static unsigned long lastmillis;
  const unsigned long pauseZeit = 5000; // in ms
  if (digitalRead(stopPin))
  {
    schritt = off;
  }
  switch (schritt)
  {
    case warten:
      if (digitalRead(startPin))
      {
        zyklus = 0;
        schritt = on;
      }
      digitalWrite(relaisRechts, relaisAus);
      digitalWrite(relaisLinks, relaisAus);
      break;
    case on:
      digitalWrite(LED_BUILTIN, HIGH);
      schritt = rechts;
      break;
    case rechts:
      digitalWrite(relaisRechts, relaisAn);
      if (digitalRead(sensorRechtsEnd))
      {
        digitalWrite(relaisRechts, relaisAus);
        schritt = haltrechts;
        lastmillis = millis();
      }
      break;
    case haltrechts:
      digitalWrite(relaisRechts, relaisAus);
      digitalWrite(relaisLinks, relaisAus);
      if (millis() - lastmillis > pauseZeit)
      {
        schritt = links;
      }
      break;
    case links:
      digitalWrite(relaisRechts, relaisAus);
      digitalWrite(relaisLinks, relaisAn);
      if (digitalRead(sensorLinksEnd))
      {
        digitalWrite(relaisLinks, relaisAus);
        schritt = haltlinks;
        lastmillis = millis();
      }
      break;
    case haltlinks:
      digitalWrite(relaisRechts, relaisAus);
      digitalWrite(relaisLinks, relaisAus);
      if (millis() - lastmillis > pauseZeit)
      {
        if (zyklus == maxzyklus)
        {
          schritt = off;
        }
        else
        {
          zyklus++; 
          schritt = rechts;
        }
      }
      break;
    case off:
      digitalWrite(LED_BUILTIN, LOW);
      schritt = warten;
      break;
  }
}

Answer 1

The const keyword tells the C/C++ compiler that the variable is a constant and cannot be changed in your code anymore.

Simply remove const and you can modify maxzyklus by using 2 digital inputs.

byte maxzyklus = 20; //max cycles