概要

ESP32 的 OTA（Over-The-Air）升級(jí)功能允許通過(guò)無(wú)線網(wǎng)絡(luò)Wi-Fi遠(yuǎn)程更新設(shè)備固件程序，無(wú)需物理連接（如 USB/UART）。比如ESP32設(shè)備在機(jī)殼內(nèi)部不好拆卸，人離設(shè)備比較遠(yuǎn)，不好接線的環(huán)境可用到OTA方式給ESP32設(shè)備下載程序。為實(shí)現(xiàn)此功能每次更新程序的時(shí)候都要在代碼里面加入OTA的相關(guān)代碼。

創(chuàng)建ESP32-OTA無(wú)線局域網(wǎng)網(wǎng)頁(yè)版遠(yuǎn)程升級(jí)入口

打開(kāi)Arduino IDE中自帶ESP32—OTAWebUpdater示例

#include < WiFi.h >
#include < WiFiClient.h >
#include < WebServer.h >
#include < ESPmDNS.h >
#include < Update.h >

const char* host = "esp32";
const char* ssid = "YXDZ1";
const char* password = "YXDZ#2023#1";

WebServer server(80);

/*
 * Login page
 */

const char* loginIndex =
 "< form name='loginForm' >"
    "< table width='20%' bgcolor='A09F9F' align='center' >"
        "< tr >"
            "< td colspan=2 >"
                "< center >< font size=4 >ESP32 Login Page< /font >< /center >"
                "
"
            "< /td >"
            "
"
            "
"
        "< /tr >"
        "< tr >"
             "< td >Username:< /td >"
             "< td >< input type='text' size=25 name='userid' >
< /td >"
        "< /tr >"
        "
"
        "
"
        "< tr >"
            "< td >Password:< /td >"
            "< td >< input type='Password' size=25 name='pwd' >
< /td >"
            "
"
            "
"
        "< /tr >"
        "< tr >"
            "< td >< input type='submit' onclick='check(this.form)' value='Login' >< /td >"
        "< /tr >"
    "< /table >"
"< /form >"
"< script >"
    "function check(form)"
    "{"
    "if(form.userid.value=='ESP32-OTA' && form.pwd.value=='ESP32-OTA')"
    "{"
    "window.open('/serverIndex')"
    "}"
    "else"
    "{"
    " alert('Error Password or Username')/*displays error message*/"
    "}"
    "}"
"< /script >";

/*
 * Server Index Page
 */

const char* serverIndex =
"< script src='http://www.makelele.cn/images/chaijie_default.png' >< /script >"
"< form method='POST' action='#' enctype='multipart/form-data' id='upload_form' >"
   "< input type='file' name='update' >"
        "< input type='submit' value='Update' >"
    "< /form >"
 "progress: 0%"
 "< script >"
  "$('form').submit(function(e){"
  "e.preventDefault();"
  "var form = $('#upload_form')[0];"
  "var data = new FormData(form);"
  " $.ajax({"
  "url: '/update',"
  "type: 'POST',"
  "data: data,"
  "contentType: false,"
  "processData:false,"
  "xhr: function() {"
  "var xhr = new window.XMLHttpRequest();"
  "xhr.upload.addEventListener('progress', function(evt) {"
  "if (evt.lengthComputable) {"
  "var per = evt.loaded / evt.total;"
  "$('#prg').html('progress: ' + Math.round(per*100) + '%');"
  "}"
  "}, false);"
  "return xhr;"
  "},"
  "success:function(d, s) {"
  "console.log('success!')"
 "},"
 "error: function (a, b, c) {"
 "}"
 "});"
 "});"
 "< /script >";

/*
 * setup function
 */
void setup(void) {
  Serial.begin(115200);

  // Connect to WiFi network
  WiFi.begin(ssid, password);
  Serial.println("");

  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());

  /*use mdns for host name resolution*/
  if (!MDNS.begin(host)) { //http://esp32.local
    Serial.println("Error setting up MDNS responder!");
    while (1) {
      delay(1000);
    }
  }
  Serial.println("mDNS responder started");
  /*return index page which is stored in serverIndex */
  server.on("/", HTTP_GET, []() {
    server.sendHeader("Connection", "close");
    server.send(200, "text/html", loginIndex);
  });
  server.on("/serverIndex", HTTP_GET, []() {
    server.sendHeader("Connection", "close");
    server.send(200, "text/html", serverIndex);
  });
  /*handling uploading firmware file */
  server.on("/update", HTTP_POST, []() {
    server.sendHeader("Connection", "close");
    server.send(200, "text/plain", (Update.hasError()) ? "FAIL" : "OK");
    ESP.restart();
  }, []() {
    HTTPUpload& upload = server.upload();
    if (upload.status == UPLOAD_FILE_START) {
      Serial.printf("Update: %sn", upload.filename.c_str());
      if (!Update.begin(UPDATE_SIZE_UNKNOWN)) { //start with max available size
        Update.printError(Serial);
      }
    } else if (upload.status == UPLOAD_FILE_WRITE) {
      /* flashing firmware to ESP*/
      if (Update.write(upload.buf, upload.currentSize) != upload.currentSize) {
        Update.printError(Serial);
      }
    } else if (upload.status == UPLOAD_FILE_END) {
      if (Update.end(true)) { //true to set the size to the current progress
        Serial.printf("Update Success: %unRebooting...n", upload.totalSize);
      } else {
        Update.printError(Serial);
      }
    }
  });
  server.begin();
}

void loop(void) {
  server.handleClient();
  delay(1);
}

并對(duì)其中的代碼做如下更改：
給ESP32開(kāi)發(fā)板連接到自己電腦所在的局域網(wǎng)的路由器WIFI上，填上WIFI名稱(chēng)ssis和密碼password

const char* host = "esp32";
const char* ssid = "YXDZ1";
const char* password = "YXDZ#2023#1";

host為ESP32作為Web服務(wù)器時(shí)，將ESP32以易記的主機(jī)名（如esp32.local）廣播到局域網(wǎng)，其他設(shè)備可直接通過(guò)該名稱(chēng)訪問(wèn)，用戶(hù)可通過(guò)http://esp32.local直接訪問(wèn)，無(wú)需記憶IP地址

const char* host = "esp32";

  /*use mdns for host name resolution*/
  if (!MDNS.begin(host)) { //http://esp32.local
    Serial.println("Error setting up MDNS responder!");
    while (1) {
      delay(1000);
    }
  }

更改好OTA無(wú)線局域網(wǎng)網(wǎng)頁(yè)版入口的用戶(hù)名和密碼，這里都更改為ESP32-OTA

"if(form.userid.value=='ESP32-OTA' && form.pwd.value=='ESP32-OTA')"

通過(guò)有線方式連接電腦和ESP32開(kāi)發(fā)板，并把代碼編譯通過(guò)先通過(guò)有線方式下載到ESP32開(kāi)發(fā)板，讓開(kāi)發(fā)板創(chuàng)建無(wú)線OTA遠(yuǎn)程升級(jí)網(wǎng)頁(yè)版入口
打開(kāi)串口助手，按下ESP32開(kāi)發(fā)板復(fù)位，會(huì)顯示出所連接的局域網(wǎng)的IP地址，mDNS域名訪問(wèn)創(chuàng)建成功。

在瀏覽器輸入IP地址或創(chuàng)建的http://esp32.local域名即可跳轉(zhuǎn)到OTA遠(yuǎn)程升級(jí)網(wǎng)頁(yè)版入口，輸入創(chuàng)建好的用戶(hù)名和密碼并登錄

此時(shí)再跳轉(zhuǎn)到程序下載界面，選擇編譯好的程序文件并上傳到開(kāi)發(fā)板內(nèi)

創(chuàng)建一個(gè)ESP32開(kāi)發(fā)板進(jìn)行OTA升級(jí)應(yīng)用程序示例

若要每次都要對(duì)ESP32開(kāi)發(fā)板進(jìn)行OTA升級(jí)，新的應(yīng)用程序中都要加入上述OTA無(wú)線局域網(wǎng)網(wǎng)頁(yè)版遠(yuǎn)程升級(jí)入口的相關(guān)代碼。下面為一個(gè)ESP32開(kāi)發(fā)板GPIO2引腳上的閃燈程序的代碼，并加入了OTA的相關(guān)代碼，然后對(duì)OTA部分的代碼進(jìn)行上述一樣的更改。

#include < WiFi.h >
#include < WiFiClient.h >
#include < WebServer.h >
#include < ESPmDNS.h >
#include < Update.h >

const char* host = "esp32";
const char* ssid = "YXDZ1";
const char* password = "YXDZ#2023#1";

//variabls to blink without delay:
const int led = 2;
unsigned long previousMillis = 0;        // will store last time LED was updated
const long interval = 1000;           // interval at which to blink (milliseconds)
int ledState = LOW;             // ledState used to set the LED

WebServer server(80);

/*
 * Login page
 */

const char* loginIndex = 
 "< form name='loginForm' >"
    "< table width='20%' bgcolor='A09F9F' align='center' >"
        "< tr >"
            "< td colspan=2 >"
                "< center >< font size=4 >ESP32 Login Page< /font >< /center >"
                "
"
            "< /td >"
            "
"
            "
"
        "< /tr >"
        "< td >Username:< /td >"
        "< td >< input type='text' size=25 name='userid' >
< /td >"
        "< /tr >"
        "
"
        "
"
        "< tr >"
            "< td >Password:< /td >"
            "< td >< input type='Password' size=25 name='pwd' >
< /td >"
            "
"
            "
"
        "< /tr >"
        "< tr >"
            "< td >< input type='submit' onclick='check(this.form)' value='Login' >< /td >"
        "< /tr >"
    "< /table >"
"< /form >"
"< script >"
    "function check(form)"
    "{"
    "if(form.userid.value=='ESP32-OTA' && form.pwd.value=='ESP32-OTA')"
    "{"
    "window.open('/serverIndex')"
    "}"
    "else"
    "{"
    " alert('Error Password or Username')/*displays error message*/"
    "}"
    "}"
"< /script >";
 
/*
 * Server Index Page
 */
 
const char* serverIndex = 
"< script src='http://www.makelele.cn/images/chaijie_default.png' >< /script >"
"< form method='POST' action='#' enctype='multipart/form-data' id='upload_form' >"
   "< input type='file' name='update' >"
        "< input type='submit' value='Update' >"
    "< /form >"
 "progress: 0%"
 "< script >"
  "$('form').submit(function(e){"
  "e.preventDefault();"
  "var form = $('#upload_form')[0];"
  "var data = new FormData(form);"
  " $.ajax({"
  "url: '/update',"
  "type: 'POST',"
  "data: data,"
  "contentType: false,"
  "processData:false,"
  "xhr: function() {"
  "var xhr = new window.XMLHttpRequest();"
  "xhr.upload.addEventListener('progress', function(evt) {"
  "if (evt.lengthComputable) {"
  "var per = evt.loaded / evt.total;"
  "$('#prg').html('progress: ' + Math.round(per*100) + '%');"
  "}"
  "}, false);"
  "return xhr;"
  "},"
  "success:function(d, s) {"
  "console.log('success!')" 
 "},"
 "error: function (a, b, c) {"
 "}"
 "});"
 "});"
 "< /script >";

/*
 * setup function
 */
void setup(void) {
  pinMode(led, OUTPUT);
  
  Serial.begin(115200);

  // Connect to WiFi network
  WiFi.begin(ssid, password);
  Serial.println("");

  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());

  /*use mdns for host name resolution*/
  if (!MDNS.begin(host)) { //http://esp32.local
    Serial.println("Error setting up MDNS responder!");
    while (1) {
      delay(1000);
    }
  }
  Serial.println("mDNS responder started");
  /*return index page which is stored in serverIndex */
  server.on("/", HTTP_GET, []() {
    server.sendHeader("Connection", "close");
    server.send(200, "text/html", loginIndex);
  });
  server.on("/serverIndex", HTTP_GET, []() {
    server.sendHeader("Connection", "close");
    server.send(200, "text/html", serverIndex);
  });
  /*handling uploading firmware file */
  server.on("/update", HTTP_POST, []() {
    server.sendHeader("Connection", "close");
    server.send(200, "text/plain", (Update.hasError()) ? "FAIL" : "OK");
    ESP.restart();
  }, []() {
    HTTPUpload& upload = server.upload();
    if (upload.status == UPLOAD_FILE_START) {
      Serial.printf("Update: %sn", upload.filename.c_str());
      if (!Update.begin(UPDATE_SIZE_UNKNOWN)) { //start with max available size
        Update.printError(Serial);
      }
    } else if (upload.status == UPLOAD_FILE_WRITE) {
      /* flashing firmware to ESP*/
      if (Update.write(upload.buf, upload.currentSize) != upload.currentSize) {
        Update.printError(Serial);
      }
    } else if (upload.status == UPLOAD_FILE_END) {
      if (Update.end(true)) { //true to set the size to the current progress
        Serial.printf("Update Success: %unRebooting...n", upload.totalSize);
      } else {
        Update.printError(Serial);
      }
    }
  });
  server.begin();
}

void loop(void) {
  server.handleClient();
  delay(1);

  //loop to blink without delay
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // if the LED is off turn it on and vice-versa:
    ledState = not(ledState);

    // set the LED with the ledState of the variable:
    digitalWrite(led, ledState);
  }
}

ESP32開(kāi)發(fā)板OTA升級(jí)下載應(yīng)用程序

編譯并導(dǎo)出可供OTA升級(jí)下載的二進(jìn)制bin應(yīng)用程序文件

在項(xiàng)目文件夾下的build文件夾里可看到可供下載的bin應(yīng)用程序文件

進(jìn)入OTA無(wú)線局域網(wǎng)網(wǎng)頁(yè)版遠(yuǎn)程升級(jí)入口，打開(kāi)應(yīng)用程序bin文件，并對(duì)ESP32開(kāi)發(fā)板進(jìn)行遠(yuǎn)程下載程序