我在ESP32上有一个Web服务器,在该服务器上有一个主页。我想每隔x秒自动更新一次主页上的传感器值(无需用户输入)。我无法访问文件系统。

传感器直接连接到ESP32。传感器值在我的C程序中,存储在变量中并定期更新。变量是全局变量,以便于使用。

我考虑过Ajax(我没有经验),但是我可以找到的所有示例和方法都使用文件从中加载数据(在XMLHttpRequest()。open(... url ....)的“url”部分中)。 )。我没有文件,只有字符串,可以在其中生成HTML和Javascript代码并将其发送给客户端。

我不知道如何更新自己的值(value)观,并希望有所帮助。

我曾考虑过尝试使用w3schools中的示例,但我不知道如何在其中获得值(value):

其他页面的示例(我不使用此代码-我无法使用文件!)

function loadDoc() {
  var xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      document.getElementById("demo").innerHTML = this.responseText;
    }
  };
  xhttp.open("GET", "ajax_info.txt", true);
  xhttp.send();
}

这是我在ESP上的C程序的一些代码:

HTML字符串:
String html_document() {
  String sHTML;
  sHTML = "<!doctype html>";
  sHTML +="<html>";
  sHTML +="<html lang=\"de\">";
  /***************** head ****************/
  sHTML +="<head>";
  /****** avoid favicon requests **  ** <link rel=\"shortcut icon\" href=\"data:image/x-icon;,\" type=\"image/x-icon\"> **/
  sHTML +="<link rel=\"icon\" href=\"data:;base64,iVBORw0KGgo=\"> ";
  sHTML +="<meta charset=\"utf-8\"><meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">";
  //Anpassung an Viewport für unterschiedliche Devices
  /***************** title ***************/
  sHTML +="<title>LetsgoING IoT</title>";
  sHTML +="<style>h1{display: flex; flex-flow: row wrap; justify-content: center;} </style>";
  sHTML +="<style>h1{ color: green;}</style>";
  sHTML +="<style>h2{display: flex; flex-flow: row wrap; justify-content: center;} </style>";
  sHTML +="<style>h2{ color: blue;}</style>";
  sHTML +="<style>h5{display: flex; flex-flow: row wrap; justify-content: center;} </style>";
  sHTML +="<style>p{display: flex; flex-flow: row wrap; justify-content: center; margin-bottom: 3%;} </style>";
  sHTML +="<style>p1{display: flex; flex-flow: row wrap; justify-content: center; margin-bottom: 0%;} </style>";
  sHTML +="<style>p2{display: flex; flex-flow: row wrap; justify-content: center; margin-bottom: 0%;} </style>";
  sHTML +="</head>";
  /***************** body ****************/
  sHTML+= "<body>";   //onload=\"window.setInterval(updateDiv, 15000);\"
  sHTML+= "<h1>LetsgoING</h1>";
  sHTML+= "<h2>Internet der Dinge</h2>";
  sHTML+= "<p1><a style=\"width:38%;\"></a><a style=\"width:20%;color: green\">LED ein</a> <a style=\"width:15%;\" href=\"LEDON\"><button> EIN </button></a> </a><a style=\"width:27%;\"> </a></p1>";
  sHTML+= "<p><a style=\"width:38%;\"></a><a style=\"width:20%;color: red\"  >LED aus</a> <a style=\"width:15%\"; href=\"LEDOFF\"><button>AUS</button></a><a style=\"width:27%;\"> </a></p>";
  sHTML+= "<h5>RGB-LED PWM-Werte</h5>";
  sHTML+= "<form><p2>";
  sHTML+= "<a style=\"width:38%;\"></a> <a style=\"width:20%;color: red\"> Rot</a>  <a style=\"width:15%;\" ><input name=\"rot\" type=\"number\" min=\"0\" max=\"255\" step=\"1\" value=\"80\" ></a><a style=\"width:27%;\"> </a>";
  sHTML+= "<a style=\"width:38%;\"></a> <a style=\"width:20%;color: green\">Grün</a><a style=\"width:15%;\" ><input name=\"gruen\" type=\"number\" min=\"0\" max=\"255\" step=\"1\" value=\"80\"></a><a style=\"width:27%;\"> </a>";
  sHTML+= "<a style=\"width:38%;\"></a> <a style=\"width:20%;color: blue\">Blau</a> <a style=\"width:15%;\" ><input name=\"blau\" type=\"number\" min=\"0\" max=\"255\" step=\"1\" value=\"80\"></a><a style=\"width:27%;\"> </a>";
  sHTML+= "</p2>";
  sHTML+= "<p><a style=\"width:38%;\"></a> <a style=\"width:20%;\">         </a>   <label style=\"width:15%;\" ><input type=\"submit\" value=\"senden\"></label><a style=\"width:27%;\"></a></p>";
  sHTML+= "</form>";
  sHTML+= "<h5>analoger Schwellwert</h5>";
  sHTML+= "<form><p2><a style=\"width:38%;\"></a> <a style=\"width:20%;\"> <input name=\"schwell\" type=\"number\" min=\"0\" max=\"1024\" step=\"10\" value=\"300\"> </a> <a style=\"width:15%;\"><input type=\"submit\" value=\"senden\"></a><a style=\"width:27%;\"> </a></p2>";
  //sHTML+= "<p><a style=\"width:28%;\"></a> <a style=\"width:30%;\">         </a>   <label style=\"width:15%;\" ><input type=\"submit\" value=\"senden\"></label><a style=\"width:27%;\"></a></p>";
  sHTML+= "</form>";
  sHTML+= "<h5>PWM-Wert</h5>";
  sHTML+= "<form><p2><a style=\"width:38%;\"></a> <a style=\"width:20%;\"> <input name=\"pwm\" type=\"number\" min=\"0\" max=\"255\" step=\"1\" value=\"0\"> </a> <a style=\"width:15%;\"><input type=\"submit\" value=\"senden\"></a><a style=\"width:27%;\"> </a></p2>";
  sHTML+= "</form>";
  sHTML+= "<h5>Messwerte</h5>";
  sHTML+="<p><a style=\"width:38%;\"></a> <p3 id=\"an1\"; style=\"width:20%;\" href=\"anlg1\">#-Wert-#</p3><a style=\"width:22%;\">Analoger Pin 36   </a><a style=\"width:20%;\"></a></p>";
  sHTML+="<p><a style=\"width:38%;\"></a> <p3 id=\"an2\"; style=\"width:20%;\">#-Wert-#</p3><a style=\"width:22%;\">Analoger Pin 39   </a><a style=\"width:20%;\"></a></p>";
  sHTML+="<p><a style=\"width:38%;\"></a> <p3 id=\"dig\"; style=\"width:20%;\">#-Wert-#</p3><a style=\"width:22%;\">Digitaler Pin 5   </a><a style=\"width:20%;\"></a></p>";
  sHTML+= "</body>";
  sHTML+= "</html>";
  return sHTML;
}

循环:
void loop() {
  if (millis() - startTime >= 2000) {
    startTime = millis();
    /* Check if a client has connected */
    client = server.available();
    if (!client){
      return;
    }
    /*Wait for the client to send data */
    Serial.println("neuer Client verbunden------------------------------");
    /*Count requests: */
    request_counter ++;
    unsigned long clTimeout = millis()+250;
    while(!client.available() && (millis()<clTimeout) ) {
      delay(1);
    }
    /***  publish Homepage ***/
    client.print(html_document());
    /* Read the first line of the clients request string "sHTML" until carriage return \r */
    sHTMLRequest = client.readStringUntil('\r');
    #ifdef DEBUGMODE
    Serial.println("Antwort: ");
    Serial.println(sHTMLRequest);
    #endif
    client.flush();
    /* stop client, if request is empty */
    if(sHTMLRequest=="") {
      Serial.println("Leere Anfrage! - client gestoppt");
      client.stop();
      return;
    }
    #ifdef DEBUGMODE
    Serial.println("Antwort2: ");
    Serial.println(sHTMLRequest);
    Serial.println ("---------");
    Serial.print("DEBUG: Remote IP - Address : ");
    for (int i = 0; i < 3; i++) {
      Serial.print( client.remoteIP()[i]);
      Serial.print(".");
    }
    Serial.println(client.remoteIP()[3]);
    Serial.print("Seitenaufrufe: ");
    Serial.println(request_counter);
    Serial.println ("---------");
    #endif
    /**** call event handler **********/
    eventHandler();
    #ifdef DEBUGMODE
    Serial.println("Zugewiesene PWM-Werte");
    Serial.print("rot: ");
    Serial.println(rot);
    Serial.print("gruen: ");
    Serial.println(gruen);
    Serial.print("blau: ");
    Serial.println(blau);
    #endif
    /* write PWM values for colors to channels*/
    ledcWrite(1, rot);
    ledcWrite(2, gruen);
    ledcWrite(3, blau);
    #ifdef DEBUGMODE
    Serial.println(analog1);
    #endif
  }
  UpdateValues();
}

/**** reads pin values **/
void UpdateValues() {
  analog1 = analogRead(pinAnalog1);
  analog2 = analogRead(pinAnalog2);
  DigiOut = digitalRead(LEDpin);
}

这是更新值并创建JSON字符串的函数:
void UpdateValues() {
  analog1 = analogRead(pinAnalog1);
  analog2 = analogRead(pinAnalog2);
  DigiOut = digitalRead(LEDpin);
  String strJson;
  strJson = "(200,\"application/json\",\"{\"pin36\": ";
  strJson+=analog1;
  strJson+=", \"pin39\":";
  strJson+= analog2;
  strJson+=", \"pin5\": ";
  strJson+=DigiOut;
  strJson+="}\")";
  server.print(strJson);
}

最佳答案

选项1 :

最简单的方法是要求页面每5秒刷新一次,方法是将其添加到<head>中:

sHTML +="<meta http-equiv=\"refresh\" content=\"5\">";

然后更改您的sHTML字符串以连接全局变量的值。每次页面刷新时,它将(应该)重建html并返回最新值。

选项2 :

您可以使用ajax来获取最新值,然后经常更新显示数据的网页的一小部分。

这里发生的是您将ESP32设置为提供第二个URL,该URL仅作为json对象返回最新值。然后将这些值注入(inject)页面,覆盖旧的页面。

首先在<head>中添加指向jQuery的链接:
sHTML +="<script src=\"https://code.jquery.com/jquery-3.2.1.min.js\"></script>";

<body>中添加带有ID的spans,以保存要更新的值。就像是:
sHTML+= "<h5>Messwerte</h5>";
sHTML+="<p>Analoger Pin 36</p>&nbsp;<span id='pin36'></span>";
sHTML+="<p>Analoger Pin 39</p>&nbsp;<span id='pin39'></span>";
sHTML+="<p>Analoger Pin 5</p>&nbsp;<span id='pin5'></span>";

为以下每5秒发出ajax请求的javascript创建sHTML,并在浏览器中更新最新值:

<script>
  $(function() {

    // request data every 5 seconds
    setInterval(requestData, 5000);

    function requestData() {

      // ajax request for latest sensor data
      $.get("/sensors")
        .done(function(data) {

          console.log(data);  // debugging - remove when satisfied

          if (data) { // if the returned data is not null, update the values
            $("#pin36").text(data.pin36);
            $("#pin39").text(data.pin39);
            $("#pin5").text(data.pin5);
          } else { // a problem occurred
            $("#pin36").text("?");
            $("#pin39").text("?");
            $("#pin5").text("?");
          }
        }).fail(function() {
          console.log("The was a problem retrieving the data.");
        });
    }

  });
</script>

当您在/sensors中检测到字符串sHTMLRequest时,您想要返回以下json格式:
{"pin36": 5.2, "pin39": 0.322, "pin5": 1}
在这一点上,我对您的设置了解不多,无法进一步建议,但是这些链接有望对C代码有所帮助:http://www.iotsharing.com/2017/05/how-to-turn-esp32-into-web-server.htmlhttp://randomnerdtutorials.com/esp32-web-server-arduino-ide/

如果您使用https://github.com/nhatuan84/esp32-webserver中的ESP32WebServer.h(有关更多详细信息,请参见http://www.iotsharing.com/2017/05/how-to-turn-esp32-into-web-server.html的后半部分),则可以使用以下方法:
server.on("/sensors", handleSensorData);


/* this callback will be invoked when user request "/sensors" */
void handleSensorData() {
  /* server responds 200 with a json payload */
  /* although preferably concatenate your real sensor data here */
  server.send(200, "application/json", "{\"pin36\": 5.2, \"pin39\": 0.322, \"pin5\": 1}");
}

07-28 02:24