Uno based GM 4 wire IAC controller

// GM IAT Controller JKW 2021
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Stepper.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#define ONE_WIRE_BUS 2
#define BACKLIGHT_PIN     3
const int stepsPerRevolution = 255; 
Stepper myStepper(stepsPerRevolution, 4, 5, 6, 7);
int stepCount = 0;         
int Step = 0;
int MinSteps = 3;
int prog = 0;
int istep = 0;
int maxtmp = 180;
int potpin = 0;
unsigned long myTime;
LiquidCrystal_I2C lcd(0x27,16,2);  // set the LCD address to 0x27 for a 16 chars and 2 line display 0X26 for 20 by 4 lcd.
OneWire oneWire(ONE_WIRE_BUS); 
DallasTemperature sensors(&oneWire);


void iprog() {
istep = map(stepCount,0,255,15,0);
lcd.setCursor(0,0);
lcd.print("Initializing!");
lcd.setCursor(0,1);
switch (istep) {
    case 1: 
      lcd.print("=>              ");
      break;
    case 2:
      lcd.print("==>             ");
      break;
    case 3: 
      lcd.print("===>            ");
      break;
    case 4: 
      lcd.print("====>           ");
      break;
    case 5: 
      lcd.print("=====>          ");
      break;
    case 6: 
      lcd.print("======>         ");
      break;
    case 7: 
      lcd.print("=======>        ");
      break;
    case 8: 
      lcd.print("========>       ");
      break;
    case 9: 
      lcd.print("=========>      ");
      break;
    case 10: 
      lcd.print("==========>     ");
      break;
    case 11: 
      lcd.print("===========>    ");
      break;
    case 12: 
      lcd.print("============>   ");
      break;
    case 13: 
      lcd.print("=============>  ");
      break;
    case 14: 
      lcd.print("==============> ");
      break;
    case 15: 
      lcd.print("===============>");
      break;
    }
 }

void homeit() {
  maxtmp = analogRead(potpin);
  lcd.clear();
  lcd.setBacklight(HIGH);
  stepCount = 0;
  while (stepCount < 255) {
  iprog();
  myStepper.step(1);
  Serial.print("steps:");
  Serial.println(stepCount);
  stepCount++;
}  
}

void setup() {
  Serial.begin(9600);
  Wire.begin();
  lcd.begin (16,2); //  <<-----  LCD 16x2
  lcd.clear();
  sensors.begin();
  delay(2000);
  homeit();
  lcd.setBacklight(HIGH);
  myTime = millis();
}

void progressBar() {
prog = map(Step,0,255,6,1);
lcd.setCursor(9,1);
switch (prog) {
    case 1: 
      lcd.print("=>     ");
      break;
    case 2:
      lcd.print("==>    ");
      break;
    case 3: 
      lcd.print("===>   ");
      break;
    case 4: 
      lcd.print("====>  ");
      break;
    case 5: 
      lcd.print("=====> ");
      break;
    case 6: 
      lcd.print("======>");
      break;
    }
}

void dhtwork() {
  sensors.requestTemperatures();
  float f = sensors.getTempFByIndex(0);
  if (isnan(f)) {
    Serial.println(F("Failed to read from DHT sensor!"));
    return;
  }  
  maxtmp = analogRead(potpin);
  maxtmp = map(maxtmp, 1, 1022, 20, 180);
  Step = constrain(map(f, -20, maxtmp, 255, 0), 0, 255);
  Serial.print(F("MaxTemp:  "));
  Serial.print(maxtmp);
  Serial.print(F("   Temperature: "));
  Serial.print(f);
  Serial.print(" ");
  lcd.setCursor(0,0);
  lcd.print("T:");
  lcd.print(f);
  lcd.print("  ");
  lcd.setCursor(9,0);
  lcd.print("Max:");
  lcd.print(maxtmp);
  lcd.print(" ");
}

void loop() {
dhtwork();
setit();
delay(25);
if ( millis() > myTime + 125000 ) {
 lcd.setBacklight(LOW);  
}
 
}

void disableStepper() {
digitalWrite(4, LOW);
digitalWrite(5, LOW);
digitalWrite(6, LOW);
digitalWrite(7, LOW);
}

void setit() {
  // added some histerysis, so were looking for at leats 3 degrees before a change.
  if (Step > stepCount + MinSteps ) {
    lcd.setBacklight(HIGH);
    myTime = millis();
    openit();
  }
  if (Step < stepCount - MinSteps ) {
    lcd.setBacklight(HIGH);
    myTime = millis();
    closeit();
  }
  Serial.print("Calculated step:");
  Serial.println(Step);
  lcd.setCursor(0,1);
  lcd.print("Step ");
  lcd.print(Step);
  if ( Step >= 100 ) {
  lcd.print(" ");  
  } else {
  lcd.print("  ");
  }
  delay(5);
  progressBar();  
}

void openit() {
  while (stepCount - MinSteps < Step) {
  myStepper.step(1);
  stepCount++;
  delay(5);
  disableStepper(); // only for locking style iac, if power is needed to prevent it moving comment out.
}
}

void closeit() {
  while (stepCount + MinSteps > Step) {
  myStepper.step(-1);
  stepCount--;
  delay(5);
  disableStepper();
}
}