derived from http://thierrydphotographe.free.fr/index.php/2023/03/13/thermal-camera-for-android-diy-do-it-yourself/

Arduino_Thermal_Camera_nolcd.ino

//Version 1.02

#include <WiFi.h>
#include <Adafruit_MLX90640.h>
Adafruit_MLX90640 mlx;
//#include <U8g2lib.h>

/*
#define SDA_PIN 41
#define SCL_PIN 40
*/
//U8G2_SSD1306_72X40_ER_F_SW_I2C u8g2(U8G2_R0, /* SCL=*/ SCL_PIN, /* SDA=*/ SDA_PIN, /* reset=*/ U8X8_PIN_NONE);


float frame[769];
float frameForSerial[769];
float frameTemp [768];
float Emissivity = 0.95F;

TaskHandle_t xHandleUpdateFrame ;
bool SerialInProgress = false;
bool CaptureFrameInProgress = false;



void WriteDisplay(String Str1, String Str2) {
  /*
  char buf1[30];
  char buf2[30];
  Str1.toCharArray(buf1,Str1.length() + 1);
  Str2.toCharArray(buf2,Str2.length() + 1);
  u8g2.clearBuffer();
  u8g2.drawStr( 0, 0, buf1);
  u8g2.drawStr( 0, 22, buf2);
  u8g2.sendBuffer();
  */
  Serial.print(Str1);
  Serial.print(" ");
  Serial.println(Str2);

}



void setup() {
  /*
  u8g2.begin();
  u8g2.setFont(u8g2_font_6x10_tf);
  u8g2.setFontRefHeightExtendedText();
  u8g2.setFontDirection(0);
  u8g2.setDrawColor(1);
  u8g2.setFontPosTop();
  */

  //Serial.setTxBufferSize (3076);  // removed?
  Serial.setRxBufferSize(20);
  Serial.begin(115200);
  
  WriteDisplay("Create a", "first array");
  float Temp = 20.18;
  for (uint8_t h=0; h<24; h++) {
    Temp++;
    for (uint8_t w=0; w<32; w++) { frame[h*32 + w] = Temp; }
  }
  copyArray(frame, frameForSerial,769);
 
  WriteDisplay("Disable", "WIFI");
  WiFi.mode(WIFI_OFF);
  WriteDisplay("INIT", "Serial");

  WriteDisplay("INIT", "MLX90640");
  xTaskCreatePinnedToCore( TaskUpdateFrame,  "TaskUpdateFrame", 10000, NULL, 1, &xHandleUpdateFrame, 0);          /* pin task to core 0 */

  WriteDisplay("INIT", "finish");
}



void loop() {
  if (Serial.available()) {
    String Data = "";
    while (Serial.available()) {
      char Temp = Serial.read();
      Data = Data + Temp;
    }
    Serial.flush();
    if (Data.startsWith("SENDDATA")) {
      while (CaptureFrameInProgress == true) {delay(1);}
      SerialInProgress = true;
      Serial.write((byte *) &frameForSerial, 3076);
      SerialInProgress = false;
    }
    else if (Data.startsWith("EMISSIVITY")) {
      Emissivity = Data.substring(Data.indexOf("|") + 1, Data.indexOf("²") - Data.indexOf("|") - 1).toFloat();
      mlx.setEmissivity(Emissivity);
    }
    else if (Data.startsWith("GETEMISSIVITY")) { Serial.print("EMISSIVITY|" + FloatToString(Emissivity, 2) + "²"); }
    else if (Data.startsWith("CHANGE4")) { mlx.setRefreshRate(MLX90640_4_HZ); }
    else if (Data.startsWith("CHANGE8")) { mlx.setRefreshRate(MLX90640_8_HZ); }
    else if (Data.startsWith("CHANGE16")) { mlx.setRefreshRate(MLX90640_16_HZ); }
    else if (Data.startsWith("HELLO4")) { mlx.setRefreshRate(MLX90640_4_HZ); Serial.print(Data); }
    else if (Data.startsWith("HELLO8")) { mlx.setRefreshRate(MLX90640_8_HZ); Serial.print(Data); }
    else if (Data.startsWith("HELLO16")) { mlx.setRefreshRate(MLX90640_16_HZ); Serial.print(Data); }
    else if (Data.startsWith("HELLO")) { mlx.setRefreshRate(MLX90640_8_HZ); Serial.print(Data); }
  }
  delay(5);
}





void TaskUpdateFrame( void *pvParameters ) {
  Wire.begin(6,7);  // init i2C using SDA=pin6, SCL=pin7
  Wire.setClock(800000L);

  if (! mlx.begin(MLX90640_I2CADDR_DEFAULT, &Wire)) {
    WriteDisplay("MLX90640", "not found!");
    while (1) {delay(1000); WriteDisplay("MLX90640", "not found!");}
  } else {
    WriteDisplay("MLX90640", "init correct");
  }
  mlx.setMode(MLX90640_INTERLEAVED);
  mlx.setResolution(MLX90640_ADC_18BIT);
  mlx.setRefreshRate(MLX90640_8_HZ);
  for( ;; )
  {
    mlx.getFrame(frameTemp);
    copyArray(frameTemp, frame,768);
    float TA = mlx.getTA();
    Emissivity = mlx.getEmissivity();
    frame[768] = TA;
    while (SerialInProgress == true) {delay(1);}
    CaptureFrameInProgress = true;
    copyArray(frame, frameForSerial,769);
    CaptureFrameInProgress = false;
    vTaskDelay( pdMS_TO_TICKS( 13 ) );
  }
}



void copyArray(float* src, float* dst, int len) {
    for (int i = 0; i < len; i++) { *dst++ = *src++; }
}


String FloatToString(float Val, byte decimal) {
  String Str = "";
  long Tmp = 0;
  if (Val < 0){Str = "-"; Val = -Val;}
  Val = (float)Val + (float)(0.5 / pow(10, decimal));
  Tmp = (long)Val;
  Str = Str + (String)Tmp;
  Val = (float)Val - (float)Tmp;
  if (decimal > 0){Str = Str + ".";}
  for (int i=0; i<decimal; i++) {
    Val = (float)Val * (float)10;
    Tmp = (long)Val;
    Str = Str + (String)Tmp;
    Val = (float)Val - (float)Tmp;
  }
  return Str;
}