ESP-NOW on 8266 with many to one setup

[pesti_r]

Hi all,

I have been using ESP-NOW for a while with one to one and one to many options. Now I decided to make a project with multiple 8266 boards and I would like to send different data from multiple boards to one receiver. I would like to separate the different incoming data on the receiver side.

I've read a lot about it, but I got stuck with it. It is working if I send the same data form all of the boards, but it isn't when I send different.

I use this tutorial to setup the ESP-NOW for many to one.
ESP-NOW: Receive Data from Multiple ESP8266 Boards (many-to-one) | Random Nerd Tutorials

The thing that I don't understand is in the receiver code, when it call the callback function.

It is from the tutorial, what should I change in the code in order to I could receive different types of data?

void OnDataRecv(uint8_t * mac_addr, uint8_t *incomingData, uint8_t len) {
  char macStr[18];
  Serial.print("Packet received from: ");
  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]);
  Serial.println(macStr);
  memcpy(&myData, incomingData, sizeof(myData));
  Serial.printf("Board ID %u: %u bytes\n", myData.id, len);
  // Update the structures with the new incoming data
  boardsStruct[myData.id-1].x = myData.x;
  boardsStruct[myData.id-1].y = myData.y;
  Serial.printf("x value: %d \n", boardsStruct[myData.id-1].x);
  Serial.printf("y value: %d \n", boardsStruct[myData.id-1].y);
  Serial.println();
}

I would like to make a network like in the picture.

Thank you for answers in advance!

[horace]

you need to have some means of identifing the different message types, e.g.

typedef struct struct_message {
  int type;
  float c;
} struct_message;
typedef struct struct_message2 {
  int type;
  String s;
} struct_message2;

// Create a struct_message called myData
struct_message myData;
struct_message2 myData2;

the structures start with an int called type which will be used to identify the message type, e.g. containing a float or a string
the transmitter would set up the type and the data float (type 0) or string (type 1), e.g.

void loop() {
  if ((millis() - lastTime) > timerDelay) {
    static int type = 0;
    if(type == 0) {
      // Set values to send
      myData.type = type; 
      myData.c = 1.2 + random(1,20); 
      type=1;
      // Send message via ESP-NOW
      esp_now_send(broadcastAddress, (uint8_t *) &myData, sizeof(myData));
    }
    else {  
      myData2.type = type; 
      Serial.print("Enter a string ? ");
      myData2.s = Serial.readStringUntil('\n');     // <<<< read string
      type=0;
      // Send message via ESP-NOW
      esp_now_send(broadcastAddress, (uint8_t *) &myData2, sizeof(myData2));
    }
    lastTime = millis();
  }
}

and the receiver when it received a message would look at the type and then extract data either float (type 0) or string (type 1)

// Callback function that will be executed when data is received
void OnDataRecv(uint8_t * mac, uint8_t *incomingData, uint8_t len) {
  Serial.print("Bytes received: ");
  Serial.println(len);
  int type;
  memcpy(&type, incomingData, sizeof(int));
  Serial.print("type: ");
  Serial.println(type);
  if(type == 0){
      memcpy(&myData, incomingData, sizeof(myData));
      Serial.print("Float: ");
      Serial.println(myData.c);
      Serial.println();
  }
  else {
      memcpy(&myData2, incomingData, sizeof(myData2));
      Serial.print("String: ");
      Serial.println(myData2.s);
      Serial.println();
  }
}

the transmitter alternates sending a float (type 0) then a string (type 1) etc etc in loop()
here is a run of the receiver

ESP-NOW initialised
Bytes received: 16
type: 1
String: hello joe


Bytes received: 8
type: 0
Float: 11.20

Bytes received: 16
type: 1
String: rrr


Bytes received: 8
type: 0
Float: 20.20

[pesti_r]

It's working in this way. Thanks a lot!