簡介

本實驗通過ESP-NOW無線通信協議實現ESP32開發板向多個ESP32/ESP 8266開發板發送數據。

讀取ESP32/ESP8266接收方Receiver的MAC地址

讀取ESP32開發板的代碼

#include < WiFi.h >
#include < esp_wifi.h >

void readMacAddress(){
  uint8_t baseMac[6];
  esp_err_t ret = esp_wifi_get_mac(WIFI_IF_STA, baseMac);
  if (ret == ESP_OK) {
    Serial.printf("%02x:%02x:%02x:%02x:%02x:%02xn",
                  baseMac[0], baseMac[1], baseMac[2],
                  baseMac[3], baseMac[4], baseMac[5]);
  } else {
    Serial.println("Failed to read MAC address");
  }
}

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

  WiFi.mode(WIFI_STA);
  WiFi.STA.begin();

  Serial.print("[DEFAULT] ESP32 Board MAC Address: ");
  readMacAddress();
}
 
void loop(){

}

通過串口讀取到接收方ESP32開發板1的MAC地址為：

同樣的方式讀取到接收方ESP32開發板2的MAC地址為：

讀取ESP8266開發板的代碼

#include < ESP8266WiFi.h >

void setup(){
  Serial.begin(115200);
  Serial.println();
  Serial.print("ESP Board MAC Address:  ");
  Serial.println(WiFi.macAddress());
}
 
void loop(){

}

讀取到接收方ESP8266開發板的MAC地址為：

ESP32發送方Sender程序

把ESP32開發板1，ESP開發板2，ESP8266開發板的MAC地址分別填入到下列代碼的broadcastAddress1[ ]，broadcastAddress2[ ]，broadcastAddress3[ ]數組中

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

// REPLACE WITH YOUR ESP RECEIVER'S MAC ADDRESS
uint8_t broadcastAddress1[] = {0x54, 0x43, 0xb2, 0x7f, 0x00, 0x60};
uint8_t broadcastAddress2[] = {0x34, 0x5f, 0x45, 0xac, 0x16, 0xc0};
uint8_t broadcastAddress3[] = {0xdc, 0x4f, 0x22, 0x23, 0xca, 0x10};

typedef struct test_struct {
  int x;
  int y;
} test_struct;

esp_now_peer_info_t peerInfo;

void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
  char macStr[18];
  Serial.print("Packet to: ");
  // Copies the sender mac address to a string
  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(macStr);
  Serial.print(" send status:t");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "Delivery Success" : "Delivery Fail");
}
 
void setup() {
 
  Serial.begin(115200);
 
  WiFi.mode(WIFI_STA);
 
  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }

  esp_now_register_send_cb(OnDataSent);

  // register peer
  peerInfo.channel = 0;  
  peerInfo.encrypt = false;
    
  memcpy(peerInfo.peer_addr, broadcastAddress1, 6);
  if (esp_now_add_peer(&peerInfo) != ESP_OK){
    Serial.println("Failed to add peer");
    return;
  }
  
  memcpy(peerInfo.peer_addr, broadcastAddress2, 6);
  if (esp_now_add_peer(&peerInfo) != ESP_OK){
    Serial.println("Failed to add peer");
    return;
  }
  memcpy(peerInfo.peer_addr, broadcastAddress3, 6);
  if (esp_now_add_peer(&peerInfo) != ESP_OK){
    Serial.println("Failed to add peer");
    return;
  }
}
 
void loop() {
  test_struct test;
  test_struct test2;
  test_struct test3;
  test.x = random(0,20);
  test.y = random(0,20);
  test2.x = random(0,20);
  test2.y = random(0,20);
  test3.x = random(0,20);
  test3.y = random(0,20);
 
  esp_err_t result1 = esp_now_send(
    broadcastAddress1, 
    (uint8_t *) &test,
    sizeof(test_struct));
   
  if (result1 == ESP_OK) {
    Serial.println("Sent with success");
  }
  else {
    Serial.println("Error sending the data");
  }
  delay(500);
  esp_err_t result2 = esp_now_send(
    broadcastAddress2, 
    (uint8_t *) &test2,
    sizeof(test_struct));

  if (result2 == ESP_OK) {
    Serial.println("Sent with success");
  }
  else {
    Serial.println("Error sending the data");
  }
  
  delay(500);  
  esp_err_t result3 = esp_now_send(
    broadcastAddress3, 
    (uint8_t *) &test3,
    sizeof(test_struct));
   
  if (result3 == ESP_OK) {
    Serial.println("Sent with success");
  }
  else {
    Serial.println("Error sending the data");
  }
  delay(2000);
}

ESP32/ESP8266接收方Receiver程序

上傳代碼到ESP32開發板1和ESP3開發板2

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

//Structure example to receive data
//Must match the sender structure
typedef struct test_struct {
  int x;
  int y;
} test_struct;

//Create a struct_message called myData
test_struct myData;

//callback function that will be executed when data is received
void OnDataRecv(const uint8_t * mac, const uint8_t *incomingData, int len) {
  memcpy(&myData, incomingData, sizeof(myData));
  Serial.print("Bytes received: ");
  Serial.println(len);
  Serial.print("x: ");
  Serial.println(myData.x);
  Serial.print("y: ");
  Serial.println(myData.y);
  Serial.println();
}
 
void setup() {
  //Initialize Serial Monitor
  Serial.begin(115200);
  
  //Set device as a Wi-Fi Station
  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 recv CB to
  // get recv packer info
  esp_now_register_recv_cb(esp_now_recv_cb_t(OnDataRecv));
}
 
void loop() {

}

ESP8266開發板接收代碼

#include < ESP8266WiFi.h >
#include < espnow.h >

//Structure example to receive data
//Must match the sender structure
typedef struct test_struct {
  int x;
  int y;
} test_struct;

//Create a struct_message called myData
test_struct myData;

//callback function that will be executed when data is received
void OnDataRecv(uint8_t * mac, uint8_t *incomingData, uint8_t len) {
  memcpy(&myData, incomingData, sizeof(myData));
  Serial.print("Bytes received: ");
  Serial.println(len);
  Serial.print("x: ");
  Serial.println(myData.x);
  Serial.print("y: ");
  Serial.println(myData.y);
  Serial.println();
}
 
void setup() {
  //Initialize Serial Monitor
  Serial.begin(115200);
  
  //Set device as a Wi-Fi Station
  WiFi.mode(WIFI_STA);

  //Init ESP-NOW
  if (esp_now_init() != 0) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }
  
  // Once ESPNow is successfully Init, we will register for recv CB to
  // get recv packer info
  esp_now_set_self_role(ESP_NOW_ROLE_SLAVE);
  esp_now_register_recv_cb(OnDataRecv);
}
 
void loop() {

}

ESP-NOW通信驗證

同時給發送方ESP32開發板，接收方ESP32開發板1，接收方ESP32開發板2，接收方ESP8266開發板供電，并打開四個串口助手觀察四個開發板的數據收發情況
若接收方都收到數據，發送方ESP32開發板會收到應答信息，串口打印各個MAC地址的接收方數據分發成功：

若有接收方沒有收到數據，發送方ESP32開發板會收到應答信息，串口打印對應的MAC地址的接收方數據分發失敗：

接收方ESP32開發板1串口打印接收到發送方發過來的隨機數據

接收方ESP32開發板2串口打印接收到發送方發過來的隨機數據

接收方ESP8266開發板串口打印接收到發送方發過來的隨機數據

總結

通過以上例程驗證了ESP32/ESP開發板之間單向一對多的ESP-NOW無線通信，接下來的篇章將繼續驗證多個的ESP32開發板之間實現多對一的ESP-NOW無線通信。

審核編輯 黃宇