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I built a safe entry mechanism and i would like the matlab to send an email alert when arduino is not communicating or sending any data to thingspeak. How do i write the program to detect system down and to send email alert?

Hi, I want to send an alert to multiple email ids when a channel event occurs(for example:sensor temperature exceeds a threshold value).How can I do it?Help is highly appreciated. Thanks in Advance!

EL TERMÓMETRO QUEDO CLAVADO EN -127°, LO RESETEE PERO AUN NO FUNCIONA, POSRA SER LA ZONDA Y SI FUESE ASÍ COMO ADQUIRIRLA-

Hello, in the free usage of ThingSpeak, minimum data rate is 15 s. I have received a message that I will run messages in a month, and I would like to reduce the data rate, but I cannot find information of neither which is the current data rate that it's established in my channels, nor how might I modify it. I would like to reduce the rate at which I send data, as I actually do not need this rate to be high, but I cannot figure out how to do it. I am afraid I know little of how to "program" thingspeak, for creating my channels I followed the tutorials on "getting started with Thingspeak", and it worked quite well, but I have no idea which is the data rate that is being used or how to modify it. I will be really greatful if somebody may help me to learn how to do this.

Just getting started with Thingspeak, I'm reading temperature, humidity and pressure from a BME280 connected to a ESP32. I have both a chart and numeric display on my channels, works great.

Can I resize the visualizations to get more on the monitor at a time? Or can I add a numeric readout that will show the last value added to the chart? Both the chart and readout use the same field info. I do see that if I hover my mouse over a point on the chart I get the value but wanted to be displayed.

Thanks for any help John

Hi, this is my first question here... hope not to bother you all. Is it possible to stop a sensor from collecting data by using ThingSpeak/MQTT broker/MQTT protocol? How? I'm working with a MAX30102 for oxigen and bpm detection and I need to stop the sensor from ThingSpeak or at least this is what I was asked to do. At the moment I can't figure out how to do this except by using the APIkey and the HTTP protocol but my task was to only use MQTT protocol. Hope someone can help me finding a new point of view about this topic/problem.

EDIT: I solved the problem. I used another client, MQTTx to be precise, in order to send messages in a field of control. So, at the beginning I had just two fields (BPM and SpO2), then I added a third field of control. The board WeMos, connected to the sensor MH-ET LIVE MAX30102 was used to process the sensor's data and send them to Thingspeak every 15 seconds wherease the client desktop MQTTx was also connected to ThingSpeak's broker and enbled for both publish and subscribe and I used it to send messages of ON and OFF, literally, as payload for the control field. This messages were passed to the callBack function and the payload was checked in order to change the state of my code, nested in a switch system. Thamk's for the help to you all :) If you're interested to the code and the settings just let me know.

I would like a free account on Thingspeak for 1 device/channel using lorawan and < 300 messages a day for non-commercial (home) use. Today I received an email from MathWorks that my trial period ends. Somewhere I read I may have indicated commercial usage when starting the Thingspeak account. But I cannot find it in Thingspeak profile, nor in my Mathworks profile. How to change this?

El termómetro quedo tildado en -127°, lo desconecte en varias oportunidades y se encuentra tildado.

Hello! A few years ago i could write data to my thingspeak field with this code on arduino with ESP8266.

However today when i try this i only get errors. Instead I have to use this code. it is almost the same but connecting without SSL on port 80 instead.

Has anything changed on thingspeaks side? What do i do wrong? Here is a link to the full code if thats needed: https://github.com/kjellcompany/Arduino_701/blob/master/Thingspeak/Thingspeak.ino

Every day, thousands of people ask questions on MATLAB Answers and many of these are about their code. Questions such as “How can I make this faster?”, “Why do I get this error message?” or “Why don’t I get the answer I expect?”. There’s often one crucial thing missing though – the code in question!

Most of the people who answer questions on MATLAB Answers are volunteers from the community. They are answering your questions for fun, to learn more about MATLAB or just because they like to be helpful. This is even true for people such as me who are MathWorks members of staff. It’s not part of my role to patrol the community, looking where I can help out. I do it because I like to do it.

Make it easier to help me help you.

Imagine you’re a volunteer, looking for something interesting to answer. What kind of questions are you more likely to dig into and help an anonymous stranger figure out?

In my case, I almost always focus on problems that I can easily reproduce. I rarely know the answer to any question off the top of my head and so what I like to do is start off with the problem you are facing and use the various tools available to me such as the profiler or debugger to figure it out. This is the fun of it all for me – I almost always learn something by doing this and you get helped out as a side effect!

The easier I can reproduce your issue, the more likely I am to get started. If I can’t reproduce anything and the answer isn’t immediately obvious to me I’ll just move onto the next question. One example that demonstrates this perfectly is a case where someone’s MATLAB code was running too slowly. All of the code was available so I could run it on my machine, profile it and provide a speed-up of almost 150x.

It's not always feasible or desirable to post all of your code in which case you need to come up with a minimal, reproducible example. What’s the smallest amount of code and data you can post that I can run on my machine and see what you see? This may be more work for you but it will greatly increase your chances of receiving an answer to your question.

Recently, 2nd Jan 2022 my logging has stopped. In My Account I see I have an expiry date of 10/Jan/2022 could this be the cause??? Specifically does a Free Account eventually expire and besides paying for a student or Home account is there anything I can do to continue using ThingSpeak at no charge? My message count is well below the maximum of 3 million per year.

Bonjour, J'utilise arduino Mega 2560 avec le shield Ethernet. Le sketch ino joint ci-après me permet de visualiser la jauge dans la page index.htm chargée sur la carte SD. ThingSpeak affiche bien le graph correspondant. Mais ma page web n'y a pas accès. Comment intégrer les codes dans la page ou dans le sketch pour cela ? Je vous joins la capture d'écran de cette page ainsi que les codes De la page et du sketch. Merci pour votre aide.

*********************************** Code Page "index.htm" ***********************************

<!DOCTYPE html>
<html>
    <head>
        <title>Arduino Internet Voltmeter</title>
        <script>
		var data_val = 0;		// raw data from Arduino analog input (0 to 1023)
		var volts = 0;			// voltage calculated from Arduino analog raw data value
		var num_updates = 0;	// number of 200ms periods used to calculate time to send data to ThingSpeak
		// gauge code
		eval(function(p,a,c,k,e,r){e=function(c){return(c<a?'':e(parseInt(c/a)))+((c=c%a)>35?String.fromCharCode(c+29):c.toString(36))};if(!''.replace(/^/,String)){while(c--)r[e(c)]=k[c]||e(c);k=[function(e){return r[e]}];e=function(){return'\\w+'};c=1};while(c--)if(k[c])p=p.replace(new RegExp('\\b'+e(c)+'\\b','g'),k[c]);return p}('t W=v(f){W.2t.3T(A);A.B={Z:2u,19:1q,1h:1q,1J:U,1b:D,K:0,V:[\'0\',\'20\',\'40\',\'2A\',\'2B\',\'D\'],2r:10,2C:M,1E:U,2q:{2D:3,2E:2},2H:M,1c:{2j:10,2m:3y,2O:\'3v\'},J:{2P:\'#4h\',V:\'#31\',2r:\'#3k\',1J:\'#37\',1E:\'#37\',3e:\'#31\',1t:{2s:\'1e(3Y, 3d, 3d, 1)\',3c:\'1e(1Y, 5I, 5E, .9)\'}},1o:[{1n:20,1D:2A,1F:\'#3j\'},{1n:2A,1D:2B,1F:\'#36\'},{1n:2B,1D:D,1F:\'#5n\'}]};t g=0,1p=A,N=0,1S=0,1G=U;A.5d=v(a){N=f.1c?g:a;t b=(f.1b-f.K)/D;1S=a>f.1b?1S=f.1b+b:a<f.K?f.K-b:a;g=a;f.1c?3l():A.1g();C A};A.3m=v(a){N=g=a;A.1g();C A};A.4T=v(){g=N=1S=A.B.K;A.1g();C A};A.4R=v(){C g};A.13=v(){};v 2k(a,b){Q(t i 4P b){z(1H b[i]=="1W"&&!(4O.4y.2V.4p(b[i])===\'[1W 4n]\')&&i!=\'Z\'){z(1H 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		// function called periodically to get analog value from Arduino using Ajax
		function GetArduinoInputs()
		{
			nocache = "&nocache=" + Math.random() * 1000000;
			var request = new XMLHttpRequest();
			request.onreadystatechange = function()
			{
				if (this.readyState == 4) {
					if (this.status == 200) {
						if (this.responseXML != null) {
							document.getElementById("input3").innerHTML =
								this.responseXML.getElementsByTagName('analog')[0].childNodes[0].nodeValue;
								data_val = this.responseXML.getElementsByTagName('analog')[0].childNodes[0].nodeValue;
								// calculate voltage
								volts = data_val * 3.5 / 1023;
								// only send data to ThingSpeak every 20 seconds or 100 x 200ms
								if (num_updates >= 100) {
									num_updates = 0;
									// send voltage to ThingSpeak

								ThingSpeakSend("xxxxxxxxxxxxxxxx", volts);	// insert your ThingSpeak Write API Key here
								
								}
								num_updates++;
						}
					}
				}
			}
			request.open("GET", "ajax_inputs" + nocache, true);
			request.send(null);
			setTimeout('GetArduinoInputs()', 200);	// send the request for Arduino analog data every 200ms
			
		}
		// function to send data to ThingSpeak
		function ThingSpeakSend(api_write_key, voltage)
		{
			var ts_req = new XMLHttpRequest();
			// GET request string - modify if more fields are needed
			var req_str = "http://api.thingspeak.com/update?key=" + api_write_key + "&field1=" + voltage;
			ts_req.onreadystatechange = function()
			{
				// not doing anything with response from ThingSpeak
			}
			// send the data to ThingSpeak
			ts_req.open("GET", req_str, true);
			ts_req.send(null);
		}
	</script>
    </head>
    <body onload="GetArduinoInputs()">
        <h1>Arduino Internet Voltmeter</h1>
        <p>Analog (A2): <span id="input3">...</span></p>
        <canvas id="an_gauge_1" data-major-ticks="0 0.5 1 1.5 2 2.5 3 3.5" data-type="canv-gauge" data-min-value="0" data-max-value="3.5" data-onready="setInterval( function() { Gauge.Collection.get('an_gauge_1').setValue(volts);}, 200);"></canvas>
        <!-- insert ThingSpeak chart code here -->

          <iframe width="450" height="260" style="border: 1px solid #cccccc;" src="https://thingspeak.com/channels/1620920/charts/1?bgcolor=%23ffffff&color=%23d62020&dynamic=true&results=60&type=line&update=20&yaxismax=4&yaxismin=0"></iframe>
  <!-- REPLACE THIS COMMENT WITH YOUR THINGSPEAK GRAPH -->
      </body>
  </html>

********************************************* Code "eth_websrv_SD_Ajax_gauge.ino" : *********************************************

#include <Ethernet.h>
#include <SD.h>
#include <ThingSpeak.h>

// size of buffer used to capture HTTP requests
#define REQ_BUF_SZ   50

// MAC address from Ethernet shield sticker under board
byte mac[] = { 0x90, 0xA2, 0xDA, 0x00, 0x1A, 0x71 };
IPAddress ip(192, 168, 1, 17); // IP address, may need to change depending on network
EthernetServer server(80);  // create a server at port 80
File webFile;               // the web page file on the SD card
char HTTP_req[REQ_BUF_SZ] = {0}; // buffered HTTP request stored as null terminated string
char req_index = 0;              // index into HTTP_req buffer

void setup()
{
  // disable Ethernet chip
  pinMode(10, OUTPUT);
  digitalWrite(10, HIGH);

    Serial.begin(9600);       // for debugging

    // initialize SD card
    Serial.println("Initializing SD card...");
    if (!SD.begin(4)) {
        Serial.println("ERROR - SD card initialization failed!");
        return;    // init failed
    }
    Serial.println("SUCCESS - SD card initialized.");
    // check for index.htm file
    if (!SD.exists("index.htm")) {
        Serial.println("ERROR - Can't find index.htm file!");
        return;  // can't find index file
    }
    Serial.println("SUCCESS - Found index.htm file.");

    Ethernet.begin(mac, ip);  // initialize Ethernet device
    server.begin();           // start to listen for clients
    Serial.print ("*\n -> Le serveur est sur l'adresse : ");
    Serial.println(Ethernet.localIP());
}

void loop()
{
    EthernetClient client = server.available();  // try to get client

    if (client)   // got client?
        {
          boolean currentLineIsBlank = true;

        while (client.connected()) 
        {
            if (client.available())    // client data available to read
                {
                char c = client.read(); // read 1 byte (character) from client
                // buffer first part of HTTP request in HTTP_req array (string)
                // leave last element in array as 0 to null terminate string (REQ_BUF_SZ - 1)
                if (req_index < (REQ_BUF_SZ - 1)) {
                    HTTP_req[req_index] = c;          // save HTTP request character
                    req_index++;
                }
                // last line of client request is blank and ends with \n
                // respond to client only after last line received
                if (c == '\n' && currentLineIsBlank) {
                    // send a standard http response header
                    client.println("HTTP/1.1 200 OK");
                    // remainder of header follows below, depending on if
                    // web page or XML page is requested
                    // Ajax request - send XML file
                    if (StrContains(HTTP_req, "ajax_inputs")) {
                        // send rest of HTTP header
                        client.println("Content-Type: text/xml");
                        client.println("Connection: keep-alive");
                        client.println();

                    // send XML file containing input states
                    XML_response(client);
                    }
                    else {  // web page request
                        // send rest of HTTP header
                        client.println("Content-Type: text/html");
                        client.println("Connection: keep-alive");
                        client.println();
                        // send web page
                        webFile = SD.open("index.htm");        // open web page file
                        if (webFile) {
                            while(webFile.available()) {
                                client.write(webFile.read()); // send web page to client
                            }
                            webFile.close();
                        }
                    }
                    // display received HTTP request on serial port
                    Serial.print(HTTP_req);
                    // reset buffer index and all buffer elements to 0
                    req_index = 0;
                    StrClear(HTTP_req, REQ_BUF_SZ);
                    break;
                }
                // every line of text received from the client ends with \r\n
                if (c == '\n') {
                    // last character on line of received text
                    // starting new line with next character read
                    currentLineIsBlank = true;
                } 
                else if (c != '\r') {
                    // a text character was received from client
                    currentLineIsBlank = false;
                }
            } // end if (client.available())
        } // end while (client.connected())
        delay(1);      // give the web browser time to receive the data
        client.stop(); // close the connection
    } // end if (client)
}

// send the XML file containing analog value
void XML_response(EthernetClient cl)
{
    int analog_val;

      cl.print("<?xml version = \"1.0\" ?>");
      cl.print("<inputs>");
      // read analog pin A2
      analog_val = analogRead(2);
      cl.print("<analog>");
      cl.print(analog_val);
      cl.print("</analog>");
      cl.print("</inputs>");
  }

// sets every element of str to 0 (clears array)
void StrClear(char *str, char length)
{
    for (int i = 0; i < length; i++) {
        str[i] = 0;
    }
}

// searches for the string sfind in the string str
// returns 1 if string found
// returns 0 if string not found
char StrContains(char *str, char *sfind)
{
    char found = 0;
    char index = 0;
    char len;
    len = strlen(str);
    if (strlen(sfind) > len) {
        return 0;
    }
    while (index < len) {
        if (str[index] == sfind[found]) {
            found++;
            if (strlen(sfind) == found) {
                return 1;
            }
        }
        else {
            found = 0;
        }
        index++;
    }

      return 0;
  }

My dear friend Ram and I have finished our latest movie series. You can watch the final movie , or see the whole series.

In this movie we show how you can use TimeControls and Reacts to control devices or to schedule your MATLAB code that you can write in ThingSpeak. We also discuss a bit about channel sharing.

Is it possible to use the REST API to create ThingHTTP requests?

I am using TX and RX pin of arduino connect to RX and TX pin of NodeMCU. The data does not received, the data upload to thingspeak is zero.