Send Data Wirelessly Between ESP32 Using ESPNow.

ESPNow1MLX90614.ino

/*
  Tutorial: Build Your Own Portable Contactless Temperature Reader
  Hardware:
  - TTGO T-Display ESP32
    https://my.cytron.io/p-ttgo-t-display-esp32-1.14-display-module-presolder-header?tracking=idris
  - MLX90614 Non-Contact Infrared Temperature Sensor
    https://my.cytron.io/p-mlx90614-non-contact-infrared-temperature-sensor?tracking=idris
  
  External libraries:
  - TFT_eSPI by Bodmer Version 1.4.20
  - Adafruit MLX90614 Library by Adafruit Version 1.0.1
  
  Created by:
  24 Mar 2020    Idris Zainal Abidin, Cytron Technologies
*/

#include <esp_now.h>
#include <WiFi.h>
#include <TFT_eSPI.h>
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_MLX90614.h>

const byte broadcastAddress[] = {0x30, 0xAE, 0xA4, 0xF6, 0xCD, 0xB8}; // Replace with your ESP board MAC Address

#define ADC_PIN 34
#define VREF    1100
#define BUTTON1 35
#define BUTTON2 0

#define FF17 &FreeSans9pt7b
#define FF21 &FreeSansBold9pt7b
#define ROW1 0,16
#define ROW2 0,38
#define ROW3 0,60
#define ROW4 0,82
#define ROW5 0,104
#define ROW6 0,126

TFT_eSPI tft = TFT_eSPI();

Adafruit_MLX90614 mlx = Adafruit_MLX90614();

float ambientCelsius = 0.0;
float objectCelsius = 0.0;
float objectCelsiusTotal = 0.0;
long prevMillis = 0;
int interval = 1000;

// callback when data is sent
void OnDataSent(const byte *mac_addr, esp_now_send_status_t status)
{
  Serial.print("\r\nLast Packet Send Status:\t");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "Delivery Success" : "Delivery Fail");
}

void setup()
{
  pinMode(BUTTON1, INPUT_PULLUP);
  pinMode(BUTTON2, INPUT_PULLUP);
  
  Serial.begin(115200);
  Serial.println();
  Serial.println("Build your own Portable Contactless Temperature Reader for Covid-19");
  Serial.println();

  WiFi.mode(WIFI_STA);

  // Init ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }

  // Once ESPNow is successfully Init, we will register for Send CB to
  // get the status of Trasnmitted packet
  esp_now_register_send_cb(OnDataSent);
  
  // Register peer
  esp_now_peer_info_t peerInfo;
  memcpy(peerInfo.peer_addr, broadcastAddress, 6);
  peerInfo.channel = 0;  
  peerInfo.encrypt = false;
  
  // Add peer        
  if (esp_now_add_peer(&peerInfo) != ESP_OK){
    Serial.println("Failed to add peer");
    return;
  }

  tft.init();
  tft.setRotation(1);
  tft.fillScreen(TFT_BLACK);
  tft.fillRect(0, 0, 240, 43, TFT_DARKGREY);
  tft.setFreeFont(FF21);
  tft.setTextColor(TFT_BLACK);
  tft.setCursor(ROW1);
  tft.print("      Portable Contactless");
  tft.setCursor(0, 35); // Row 2
  tft.print("      Temperature Reader");
  tft.setTextColor(TFT_WHITE);
  tft.setCursor(ROW3);
  tft.print("         Battery:");
  tft.setTextColor(TFT_CYAN);
  tft.setCursor(ROW4);
  tft.print("   < Press button to read >");
  tft.setTextColor(TFT_WHITE);
  tft.setCursor(ROW5);
  tft.print("         Celsius:");
  tft.fillRect(0, 112, 240, 23, TFT_MAROON);
  tft.setTextColor(TFT_BLACK);
  tft.setCursor(0, 128); // Row 6
  tft.print("   #Covid19             by Idris");

  mlx.begin();
}

void loop()
{
  if (millis() - prevMillis > interval) {

    int adc = analogRead(ADC_PIN);
    float batteryVoltage = ((float)adc/4095.0)*2.0*3.3*(VREF/1000.0);
    tft.fillRect(140, 48, 100, 20, TFT_BLACK);
    if (batteryVoltage > 4.2) {
      tft.setTextColor(TFT_BLUE);
      tft.setCursor(140, 60);
      tft.print("Charge");
    }
    else {
      batteryVoltage = constrain(batteryVoltage, 3, 4); 
      float batteryPercent = ((batteryVoltage - 3) / 1) * 100;
      if (batteryPercent < 50) {
        tft.setTextColor(TFT_RED);
      }
      else if (batteryPercent < 80) {
        tft.setTextColor(TFT_YELLOW);
      }
      else {
        tft.setTextColor(TFT_GREEN);
      }
      tft.setCursor(150, 60);
      tft.print((int)batteryPercent);
      tft.print(" %");
    }
    
    prevMillis = millis();
  }

  if (digitalRead(BUTTON2) == LOW) {

    objectCelsiusTotal = 0.0;
    for (int i = 0; i < 20; i++) {
//      ambientCelsius = mlx.readAmbientTempC();
      objectCelsius = mlx.readObjectTempC();
      objectCelsiusTotal += objectCelsius;
      delay(50);
    }
    objectCelsius = objectCelsiusTotal / 20;
    int celsius = objectCelsius;
    
    tft.fillRect(140, 92, 100, 14, TFT_BLACK);
    tft.setTextColor(TFT_GREEN);
    tft.setCursor(150, 104);
    tft.print(objectCelsius);

    esp_err_t result = esp_now_send(broadcastAddress, (uint8_t *) &celsius, sizeof(celsius));

    if (result == ESP_OK) {
      Serial.println("Sent with success");
    }
    else {
      Serial.println("Error sending the data");
    }
  }
}

ESPNow2DotMatrix.ino

/*
  Project: Wireless Display with ESPNow
  Board: ESP32 Dev Module
  Mac Address: 30:AE:A4:F6:CD:B8

  Hardware:
  - Node32 Lite
    https://my.cytron.io/p-node32-lite-wifi-and-bluetooth-development-kit?tracking=idris
  - 4 In 1 MAX7219 Dot Matrix Display Module
    https://my.cytron.io/p-4-in-1-max7219-dot-matrix-display-module?tracking=idris
  
  Connections:
  ESP32 | Dot Matrix
    RAW - VCC
    GND - GND
     27 - DIN
     26 - CS
     25 - CLK
  
  External libraries:
  - MD_MAX72XX by majicDesigns Version 3.2.1 (Manager)
  - MD_Parola by majicDesigns Version 3.3.0 (Manager)

  Created by:
  24 Mar 2020    Idris Zainal Abidin, Cytron Technologies
 */

#include <esp_now.h>
#include <WiFi.h>

#include <MD_Parola.h>
#include <MD_MAX72xx.h>
#include <SPI.h>

#define HARDWARE_TYPE MD_MAX72XX::FC16_HW
//#define HARDWARE_TYPE MD_MAX72XX::ICSTATION_HW
#define MAX_DEVICES 4
#define CLK_PIN   25 // 18 or 25
#define DATA_PIN  27 // 16 or 27
#define CS_PIN    26 // 17 or 26

MD_Parola DotMatrix = MD_Parola(HARDWARE_TYPE, DATA_PIN, CLK_PIN, CS_PIN, MAX_DEVICES);

#define BUZZER  23

#define NOTE_C4  262
#define NOTE_D4  294
#define NOTE_G4  392
#define NOTE_A4  440

#define playReadyMelody() playTone(melody1, melody1Dur, 2)
#define playNote1() playTone(melody2, melody2Dur, 1)
#define playNote2() playTone(melody3, melody3Dur, 1)
#define playBatteryWeak() playTone(melody4, melody1Dur, 2)

int melody1[] = {NOTE_C4, NOTE_G4};
int melody1Dur[] = {12, 8};
int melody2[] = {NOTE_A4};
int melody2Dur[] = {8};
int melody3[] = {NOTE_D4};
int melody3Dur[] = {8};
int melody4[] = {NOTE_G4, NOTE_C4};
int melody4Dur[] = {12, 8};

int celsius;
char textDotMatrix[6];

// callback when data is recv from Master
void OnDataRecv(const uint8_t *mac_addr, const uint8_t *incomingData, int data_len) {
  char macStr[18];
  snprintf(macStr, sizeof(macStr), "%02x:%02x:%02x:%02x:%02x:%02x",
           mac_addr[0], mac_addr[1], mac_addr[2], mac_addr[3], mac_addr[4], mac_addr[5]);
  
  memcpy(&celsius, incomingData, sizeof(celsius));
  String text = String(celsius) + " °C";
  
  Serial.print("Last Packet Recv from: "); Serial.println(macStr);
  Serial.print("Last Packet Recv Data: "); Serial.println(text);
  Serial.println(" °C");

  sprintf(textDotMatrix, "%d\x90""C", (int)celsius);
  DotMatrix.write(textDotMatrix);

  playNote1();
}

void setup()
{
  Serial.begin(115200);

  DotMatrix.begin();
  DotMatrix.setIntensity(1);

  DotMatrix.setTextAlignment(PA_CENTER);
  DotMatrix.print("...");

  WiFi.mode(WIFI_STA);

  // Init ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }

  DotMatrix.setTextAlignment(PA_CENTER);
  DotMatrix.print("Ready");
  
  // Once ESPNow is successfully Init, we will register for recv CB to
  // get recv packer info
  esp_now_register_recv_cb(OnDataRecv);

  playReadyMelody();
}

void loop()
{
  
}

const int FREQUENCY = 2000;
const int CHANNEL = 0;
const int RESOLUTION = 8;
void playTone(int *melody, int *melodyDur, int notesLength)
{
  for (int i = 0; i < notesLength; i++) {
    ledcAttachPin(BUZZER, CHANNEL);
    int noteDuration = 1000 / melodyDur[i];
    ledcWriteTone(CHANNEL, melody[i]);
    int pauseBetweenNotes = noteDuration * 1.30;
    delay(pauseBetweenNotes);
    ledcDetachPin(BUZZER);
    ledcWrite(CHANNEL, 0);
  }
}