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ESP-NOW with ESP8266 - Two way communication test done

2025.04.11 05:20

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ESP-NOW with ESP8266 - Two way communication test done with my own data type transmitted back and force.

 

esp-now_2way_comm_succeed.jpg

 

Test coding done : 

===========================================================

/* Original code is from Rui Santos' humidity & temperature sensor monitor code
  His original source is at https://RandomNerdTutorials.com/esp-now-two-way-communication-esp8266-nodemcu/
 
  My code is simplified version to fit my own purpose.
  In this code, the sensor section is yet done
*/
 
#include <ESP8266WiFi.h>
#include <espnow.h>
 
// #include <Adafruit_Sensor.h>
 
// REPLACE WITH THE MAC Address of your receiver (My Net Module attached to PC)
//uint8_t broadcastAddress[] = {0xEC, 0xFA, 0xBC, 0xA7, 0xAB, 0x6D}; // NETWORK'S MAC Address
uint8_t broadcastAddress[] = {0xEC, 0xFA, 0xBC, 0xA7, 0xAE, 0xBF}; // COROLLA'S MAC Address
//COROLLA'S MAC Address:  EC:FA:BC:A7:AE:BF
//HONDA'S MAC Address:    3C:71:BF:3A:D1:3D
//CAMRY'S MAC Address:    
//NETWORK'S MAC Address:  EC:FA:BC:A7:AB:6D
 
// Digital pin connected to the relay to turn on/off 12V LED
#define BLINKING_12V_LED 2
 
// Which auto station is this code will be uploaded to  (Sender's Station ID) :
#define STATION_ID 0  // NETWORK NODE
//#define STATION_ID 1  // MY TOYOTA COROLLA
// #define STATION_ID 2  // MY HONDA PILOT
// #define STATION_ID 3  // MY TOYOTA CAMRY
 
#define STATE_OK  1000 //  Peaceful  
#define STATE_HOOD_OPEN  1001 // Car's front panel is open
#define STATE_TILTED  1002  // Car is lifted from one side (Possibly Tire or CAT Robbery)
#define STATE_SHAKING  1003 // Car is violently shaking from one side
#define STATE_TILTED_SHAKING  1004 // Tire or CAT Robbery Situation
 
// Define variables to store incoming readings
int incomingStation;
int incomingStatus;
 
// message sending every 1 seconds
const long interval = 1000;
unsigned long previousMillis = 0;    // will store last time message was updated
 
// Previous Built-in LED blining status
bool prevBuiltInLED = 0;
 
// Variable to store if sending data was successful
String success;
 
//Structure example to send data must match the receiver structure
typedef struct struct_message {
    int station;
    int status;
} struct_message;
 
// Create a struct_message called StatusReading to hold car status reading
struct_message StatusReading;
 
// Create a struct_message to hold incoming car status reading
struct_message incomingReadings;
 
// Callback when data is sent
void OnDataSent(uint8_t *mac_addr, uint8_t sendStatus) {
  Serial.print("Last Packet Send Status: ");
  if (sendStatus == 0){
    Serial.println("Delivery success");
  }
  else{
    Serial.println("Delivery fail");
  }
}
 
// Callback when data is received
void OnDataRecv(uint8_t * mac, uint8_t *incomingData, uint8_t len) {
  memcpy(&incomingReadings, incomingData, sizeof(incomingReadings));
  Serial.print("Bytes received: ");
  Serial.println(len);
 
  if (len > 0) {  // if there was any data received, reverse built-in LED (Blink)
     if (prevBuiltInLED == 0) {
        prevBuiltInLED = 1;
        digitalWrite(LED_BUILTIN, LOW);
     } else {
        prevBuiltInLED = 0;
        digitalWrite(LED_BUILTIN, HIGH);
     };    
  };
 
  incomingStation = incomingReadings.station;
  incomingStatus = incomingReadings.status;
}
 
void getReadings(){
  // Do your sensor reading and analysis here.
  // Build up the data.
}
 
void printIncomingReadings(){
  // Display Readings in Serial Monitor
  Serial.println("INCOMING READINGS");
  Serial.print("Station: ");
  Serial.print(incomingStation);
 
  Serial.print("    Status: ");
  Serial.println(incomingStatus);
}
 
void setup() {
  // Init Serial Monitor
  Serial.begin(115200);
 
  // Initialize the LED_BUILTIN pin as a debug output
  pinMode(LED_BUILTIN, OUTPUT);  
  pinMode(BLINKING_12V_LED, OUTPUT);  
 
  // Set device as a Wi-Fi Station
  WiFi.mode(WIFI_STA);
  WiFi.disconnect();
 
  // Init ESP-NOW
  if (esp_now_init() != 0) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }
 
  // Set ESP-NOW Role
  esp_now_set_self_role(ESP_NOW_ROLE_COMBO);
 
  // 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_add_peer(broadcastAddress, ESP_NOW_ROLE_COMBO, 1, NULL, 0);
 
  // Register for a callback function that will be called when data is received
  esp_now_register_recv_cb(OnDataRecv);
}
 
void loop() {
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    // save the last time you updated the Status values
    previousMillis = currentMillis;
 
    getReadings();  // Now it doesn't do anything (No sensor code is done yet)
 
    //Set values to send
    StatusReading.station = STATION_ID;
    StatusReading.status = STATE_OK;  // for now it is fixed, no sensor is yet attached
 
    // Send message via ESP-NOW
    esp_now_send(broadcastAddress, (uint8_t *) &StatusReading, sizeof(StatusReading));
 
    // Print incoming readings
    printIncomingReadings();
  }
}

 

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