ESP32 with ESPnow - slave sending back to master

[wupperpi]

Hallo,
I'm struggling to get an ESP32-slave send data back to an ESP32-master (this works fine with an ESP8266). Master-Code ist basic-master-example-code from Arduino-IDE with an addinitonal callback function for receiving.

Code: Select all

// callback when data is sent from Slave To Master
void onDataRecv(const uint8_t *mac_addr, const uint8_t *r_data, int data_len) {
  char macStr[18];
  uint8_t inData;  
  //MAC Adresse slave as info
  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(&inData, r_data, sizeof(inData));
  Serial.print  ("received : ");
  Serial.println(inData);
}
}

Slave-Code ist basic-slave-example-code from Arduino-IDE with addinitonal code for responding

Code: Select all

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

#define CHANNEL 1

uint8_t data = 0;

// Init ESP Now with fallback
void InitESPNow() {
//  WiFi.disconnect();
  if (esp_now_init() == ESP_OK) {
    Serial.println("ESPNow Init Success");
  }
  else {
    Serial.println("ESPNow Init Failed");
    // Retry InitESPNow, add a counte and then restart?
    // InitESPNow();
    // or Simply Restart
    ESP.restart();
  }
}

// config AP SSID
void configDeviceAP() {
  const char *SSID = "Slave_1";
  bool result = WiFi.softAP(SSID, "Slave_1_Password", CHANNEL, 0);
  if (!result) {
    Serial.println("AP Config failed.");
  } else {
    Serial.println("AP Config Success. Broadcasting with AP: " + String(SSID));
  }
}

void setup() {
  Serial.begin(115200);
  Serial.println("ESPNow/Basic/Slave Example");
  //Set device in AP mode to begin with
  WiFi.mode(WIFI_AP);
  // configure device AP mode
  configDeviceAP();
  
  // This is the mac address of the Slave in AP Mode
  Serial.print("AP MAC: "); Serial.println(WiFi.softAPmacAddress());
  Serial.print("STA MAC: "); Serial.println(WiFi.macAddress());
   // Init ESPNow with a fallback logic
  InitESPNow();
  // Once ESPNow is successfully Init, we will register for recv CB to
  // get recv packer info.
  esp_now_register_recv_cb(OnDataRecv);
}

// callback when data is recv from Master
void OnDataRecv(const uint8_t *mac_addr, const uint8_t *r_data, int data_len) {
  char macStr[18];
  uint8_t inData;    
  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.print("Last Packet Recv from: "); Serial.println(macStr);
  Serial.print("Last Packet Recv Data: "); Serial.println(*r_data);

  data++;
  int ret = esp_now_send(mac_addr, &data, sizeof(data)); 
  if (ret != ESP_OK ){
    Serial.print ("Error sending message!! ");
    if (ret == ESP_ERR_ESPNOW_NOT_INIT) Serial.println("ESPNOW is not initialized");
    if (ret == ESP_ERR_ESPNOW_ARG) Serial.println("invalid argument");
    if (ret == ESP_ERR_ESPNOW_INTERNAL) Serial.println("internal error");
    if (ret == ESP_ERR_ESPNOW_NO_MEM) Serial.println("out of memory");
    if (ret == ESP_ERR_ESPNOW_NOT_FOUND) Serial.println("peer is not found");
    if (ret == ESP_ERR_ESPNOW_IF) Serial.println("current WiFi interface doesn’t match that of peer");
  } else {
    Serial.print  ("send back :");
    Serial.println(data); 
  }     
  Serial.println("");
}

void loop() {

  delay(1500);
}

The slave-output ist

Last Packet Recv from: 3c:71:bf:9d:dd:ec
Last Packet Recv Data: 69
Error sending message!! peer is not found

Last Packet Recv from: 3c:71:bf:9d:dd:ec
Last Packet Recv Data: 70
Error sending message!! peer is not found

The code for ESP8266 - working fine - is:

Code: Select all

#include <ESP8266WiFi.h>
extern "C"{
#include <espnow.h>
}

#define CHANNEL 1

uint8_t data = 0;
void on_receive_data(uint8_t *mac, uint8_t *r_data, uint8_t len) {
    char MACmaster[6];
    uint8_t inData;      
    sprintf(MACmaster, "%02X:%02X:%02X:%02X:%02X:%02X",mac[0],mac[1],mac[2],mac[3],mac[4],mac[5]);
    Serial.print  ("received from MAC: ");
    Serial.println(MACmaster);
    memcpy(&inData, r_data, sizeof(inData));
    Serial.print  ("received : ");
    Serial.println(inData);

    data++;
    esp_now_send(mac, &data, sizeof(data));
    Serial.print  ("send back :");
    Serial.println(data); 
    Serial.println();       
  };
 

void setup() {
  Serial.begin(115200); Serial.println();
  WiFi.mode(WIFI_AP);
  char* SSID = "Slave_1";
  bool ret = WiFi.softAP(SSID, "Slave_1_Password", CHANNEL, 0);
  if (!ret) {
    Serial.println("AP Config failed.");
  } else {
    Serial.println("AP Config Success. Broadcasting with AP: " + String(SSID));
  }
  if (esp_now_init()!=0) {
    Serial.println("not initialized...");
    ESP.restart();
    delay(1);
  }
   Serial.print("AP MAC : " + String (WiFi.softAPmacAddress()) );
  Serial.print("STA MAC: " + String (WiFi.macAddress()) );
  esp_now_set_self_role(2); 
  esp_now_register_recv_cb(on_receive_data);   
}

void loop() {

  delay(1500);  
}

What am I doing wrong? How do I get ESP32 to work as a responding slave?

Thank you so much
wupperpi

[wupperpi]

solved it after a lond and dark night; need to pair the slave like this:

Code: Select all

uint8_t masterMac [] = {0x3C, 0x71, 0xBF, 0x9D, 0xDD, 0xEC};
esp_now_peer_info_t master;
const esp_now_peer_info_t *masterNode = &master;
const byte maxDataFrameSize = 250;
uint8_t dataToSend [maxDataFrameSize];
memcpy (&master.peer_addr, &masterMac, 6);
master.channel = CHANNEL;
master.ifidx = ESP_IF_WIFI_AP;
esp_now_add_peer (masterNode);

Have some fun