Why did my Thinkspeak channel suddenly stop receiving data?

I've been uploading data from a set of moisture sensors to 6 channels on thingspeak (4 in one account and 2 in another). I am using free versions. I will be uploading less that 1000 messages a day, and there are large intervals inbetween the channels. This system worked fine for the past three weeks or so, but on the 24th of April, the data simply stopped uploading. I first tried to change the API key, then I tried to delete a channel and try again. I even tried sending sample data with no real values using a simplified code. Nothing seems to work. Any idea what may have happened? I am sending the code I've used for reference.

//****************************Connections*****************************//
//D0 ----------> EN   (Mux)

//D1 ----------> SCL  (Screen)
//D2 ----------> SDA  (Screen)
//D3 ----------> Temp Data   (DS18B20)
//D4 ----------> S0   (Mux)
//D5 ----------> S1   (Mux)
//D6 ----------> S2   (Mux)

//D7 ----------> S3   (Mux)
//D8 ----------> Relay
//A0 ----------> Z    (Mux)
//********************************************************************//

//******************************DS18B20******************************//
#include <OneWire.h>
#include <DallasTemperature.h>
#define ONE_WIRE_BUS 0
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
DeviceAddress sensor1 =  {0x28, 0x90, 0x7F, 0xC7, 0x1F, 0x13, 0x1, 0xE0 }; //34
DeviceAddress sensor2 = { 0x28, 0xAA, 0x5E, 0x50, 0x19, 0x13, 0x2, 0xA3 }; //04
DeviceAddress sensor3 = { 0x28, 0x60, 0xF4, 0xB8, 0x1F, 0x13, 0x1, 0x1B }; //05
DeviceAddress sensor4 = { 0x28, 0xAA, 0xA2, 0xC, 0x19, 0x13, 0x2, 0xEE }; //03
DeviceAddress sensor5 = { 0x28, 0xAA, 0x9B, 0xF, 0x19, 0x13, 0x2, 0x11 }; //01
DeviceAddress sensor6 = { 0x28, 0xAA, 0x89, 0xF, 0x19, 0x13, 0x2, 0xEE }; //30
DeviceAddress sensor7 = { 0x28, 0xAA, 0xA8, 0xBB, 0x18, 0x13, 0x2, 0xEF }; //02
DeviceAddress sensor8 = { 0x28, 0xAA, 0xC5, 0x5D, 0x19, 0x13, 0x2, 0xF9 }; //32
DeviceAddress sensor9 = { 0x28, 0x36, 0x74, 0x45, 0x92, 0x18, 0x2, 0x13 }; //22
DeviceAddress sensor10 = { 0x28, 0x4F, 0xD2, 0x3C, 0x2F, 0x14, 0x1, 0x8A }; //31
DeviceAddress sensor11 = { 0x28, 0x2, 0x92, 0x45, 0x92, 0x18, 0x2, 0x64 }; //21
DeviceAddress sensor12 = { 0x28, 0xAA, 0x1D, 0x0, 0x19, 0x13, 0x2, 0xDC }; //33
DeviceAddress sensor13 = { 0x28, 0x7B, 0x1B, 0x45, 0x92, 0x5, 0x2, 0x37 }; //28
DeviceAddress sensor14 = { 0x28, 0xB6, 0x0, 0x45, 0x92, 0x11, 0x2, 0x39 }; //14
//********************************************************************//

//******************************74HC4067******************************//
#include "MUX74HC4067.h"
//********************************************************************//

//*******************************SCREEN*******************************//
//SCL ----------> D1
//SDA ----------> D2

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     LED_BUILTIN //4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
//********************************************************************//

//******************************74HC4067******************************//
// Creates a MUX74HC4067 instance
// 1st argument is the Arduino PIN to which the EN pin connects
// 2nd-5th arguments are the Arduino PINs to which the S0-S3 pins connect
//MUX74HC4067 mux(7, 8, 9, 10, 11); //Arduino
MUX74HC4067 mux(16, 2, 14, 12, 13);    //NodeMCU
//********************************************************************//

//******************************Internet******************************//
#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ThingSpeak.h>
const char* ssid = "SSID";
const char* password = "PASSWORD";
WiFiClient client;
unsigned long Channel1 = censored;  //2021 Moisture Set 1
const char * myWriteAPIKey1 = "censored";
unsigned long Channel2 = censored; //2021 Moisture Set 2
const char * myWriteAPIKey2 = "censored";
unsigned long Channel3 = censored;  //2021 Moisture Set 3
const char * myWriteAPIKey3 = "censored";
unsigned long Channel4 = censored; //2021 Temperature Set 1
const char * myWriteAPIKey4 = "censored";
unsigned long Channel5 = censored; //2021 Temperature Set 2
const char * myWriteAPIKey5 = "censored";
//********************************************************************//

//*****************************Constants******************************//
int timeBetweenReadings  = 60000; //1 minute
//int delayForNewReadingCycle = 900000; //15 minutes
//int delayForNewReadingCycle = 1800000; //30 minutes
int delayForNewReadingCycle = 2400000; //40 minutes
int MuxValues[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
//********************************************************************//

//**************************Important pins****************************//
#define relayPin 15
//********************************************************************//

void startup()
{
  Serial.println(".");
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");
  // Print the IP address
  Serial.println(WiFi.localIP());
  ThingSpeak.begin(client);
  delay(3000);
}
//********************************************************************//

void readMuxVal(int x) {
  int data = 0;
  int mPerc = 0;
  data = mux.read(x);   // Reads from channel i. Returns a value from 0 to 1023
  mPerc=(-0.000000001219500040736946*(pow(data,4)))+(0.000002433251912455929*(pow(data,3)))+(-0.001531281295811*(pow(data,2)))+(0.227285203001156*(data))+(102.9068673556674);
  Serial.print("Potentiometer at channel ");
  Serial.print(x);
  Serial.print(" is at ");
  Serial.print(data);
  Serial.print(" (");
  Serial.print((double)(data) * 100 / 1023);
  Serial.print("%%");
  Serial.println(")");

  display.setTextSize(1);             // Normal 1:1 pixel scale
  display.setTextColor(WHITE);        // Draw white text
  if (x >= 0 && x <= 4) display.setCursor(10, ((8 * x) + 17));
  if (x >= 5 && x <= 7) display.setCursor(70, ((8 * x) - 23));
  if (x >= 8 && x <= 11) display.setCursor(10, ((8 * x) - 47));
  if (x >= 12 && x <= 15) display.setCursor(70, ((8 * x) - 79));
  display.print("Y");
  display.print(x);
  display.print(":");
  display.print(mPerc);
  display.print("%");
  if (x >= 0 && x <= 3) 
  {
    ThingSpeak.writeField(Channel1, (x+1), mPerc, myWriteAPIKey1);
    delay (40000);
    ThingSpeak.writeField(Channel1, (x+5), data, myWriteAPIKey1);
  }
  if (x >= 4  && x <= 7) 
  {
    ThingSpeak.writeField(Channel2, (x-3), mPerc, myWriteAPIKey2);
    delay (40000);
    ThingSpeak.writeField(Channel2, (x+1), data, myWriteAPIKey2);
  }
  if (x >= 8 && x <= 11) 
  {
    ThingSpeak.writeField(Channel3, (x-7), mPerc, myWriteAPIKey3);
    delay (40000);
    ThingSpeak.writeField(Channel3, (x-3), data, myWriteAPIKey3);
  }
 
  display.display();
  MuxValues[x] = mPerc;
  delay (timeBetweenReadings);
}


void setup()
{
  //******************************74HC4067******************************//
  Serial.begin(9600);  // Initializes serial port
  // Waits for serial port to connect. Needed for Leonardo only
  while ( !Serial ) ;

  // Configures how the SIG pin will be interfaced
  // e.g. The SIG pin connects to PIN A0 on the Arduino,
  //      and PIN A0 is a analog input
  mux.signalPin(A0, INPUT, ANALOG);
  //********************************************************************//

  //*******************************SCREEN*******************************//
  // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println("SSD1306 allocation failed");
    for (;;); // Don't proceed, loop forever
  }
  //********************************************************************//

  //*******************************RELAY********************************//
  pinMode(relayPin, OUTPUT);
  //********************************************************************//

  //******************************DS18B20******************************//
  sensors.begin();
  //********************************************************************//


}

// Reads the 16 channels and reports on the serial monitor
// the corresponding value read by the A/D converter
void loop()
{
  digitalWrite(relayPin, LOW);
  
  display.clearDisplay();
  display.setTextSize(2);             // Normal 1:1 pixel scale
  display.setTextColor(WHITE);        // Draw white text
  display.setCursor(0,20);             // Start at top-left corner
  display.print("Connecting...");
  display.print(ssid);
  display.display();

  startup();

  if (WiFi.status() != WL_CONNECTED)
  {
    Serial.println("WiFi disconnected, reconnecting now.");
    startup();
  }

  float data = 0;

  display.clearDisplay();
  display.setTextSize(1);             // Normal 1:1 pixel scale
  display.setTextColor(WHITE);        // Draw white text
  display.setCursor(0, 0);            // Start at top-left corner
  display.println("Connected to");
  display.print(ssid);

  digitalWrite(relayPin, HIGH);
  readMuxVal(0);
  readMuxVal(1);
  readMuxVal(2);
  readMuxVal(3);
  readMuxVal(4);
  readMuxVal(5);
  readMuxVal(6);
  readMuxVal(7);

  display.clearDisplay();
  display.setTextSize(1);             // Normal 1:1 pixel scale
  display.setTextColor(WHITE);        // Draw white text
  display.setCursor(0, 0);            // Start at top-left corner
  display.println("Connected to");
  display.print(ssid);
  
  readMuxVal(8);
  readMuxVal(9);
  readMuxVal(10);
  readMuxVal(11);

  display.clearDisplay();
  display.setTextSize(1);             // Normal 1:1 pixel scale
  display.setTextColor(WHITE);        // Draw white text
  display.setCursor(0, 0);            // Start at top-left corner
  display.println("Connected to");
  display.print(ssid);

  Serial.print("Requesting temperatures...");
  sensors.requestTemperatures(); // Send the command to get temperatures
  Serial.println("DONE");

  Serial.print("Sensor 1(*C): ");
  data = sensors.getTempC(sensor1);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel4, (1), data, myWriteAPIKey4);      
    }
  display.setCursor(10, 24);
  display.print("T1: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 2(*C): ");
  data = sensors.getTempC(sensor2);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel4, (2), data, myWriteAPIKey4);   
    }
  display.setCursor(10, 32);
  display.print("T2: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  digitalWrite(relayPin, LOW);  //RELAY PIN SWITCHES OFF HERE
  
  Serial.print("Sensor 3(*C): ");
  data = sensors.getTempC(sensor3);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel4, (3), data, myWriteAPIKey4);   
    }
  display.setCursor(10, 40);
  display.print("T3: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 4(*C): ");
  data = sensors.getTempC(sensor4);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel4, (4), data, myWriteAPIKey4);   
    }
  display.setCursor(10, 48);
  display.print("T4: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 5(*C): ");
  data = sensors.getTempC(sensor5);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel4, (5), data, myWriteAPIKey4);   
    }
  display.setCursor(10, 56);
  display.print("T5: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 6(*C): ");
  data = sensors.getTempC(sensor6);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel4, (6), data, myWriteAPIKey4);   
    }
  display.setCursor(70, 24);
  display.print("T6: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 7(*C): ");
  data = sensors.getTempC(sensor7);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel4, (7), data, myWriteAPIKey4);   
    }
  display.setCursor(70, 32);
  display.print("T7: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 8(*C): ");
  data = sensors.getTempC(sensor8);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel4, (8), data, myWriteAPIKey4);   
    }
  display.setCursor(70, 40);
  display.print("T8: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 9(*C): ");
  data = sensors.getTempC(sensor9);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel5, (1), data, myWriteAPIKey5);   
    }
  display.setCursor(70, 48);
  display.print("T9: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 10(*C): ");
  data = sensors.getTempC(sensor10);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel5, (2), data, myWriteAPIKey5); 
    }
  display.setCursor(70, 56);
  display.print("T10: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  display.clearDisplay();
  display.setTextSize(1);             // Normal 1:1 pixel scale
  display.setTextColor(WHITE);        // Draw white text
  display.setCursor(0, 0);            // Start at top-left corner
  //display.print("Readings");
  display.println("Connected to");
  display.print(ssid);

  Serial.print("Sensor 11(*C): ");
  data = sensors.getTempC(sensor11);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel5, (3), data, myWriteAPIKey5); 
    }
  display.setCursor(10, 24);
  display.print("T11: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 12(*C): ");
  data = sensors.getTempC(sensor12);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel5, (4), data, myWriteAPIKey5); 
    }
  display.setCursor(10, 32);
  display.print("T12: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 13(*C): ");
  data = sensors.getTempC(sensor13);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel5, (5), data, myWriteAPIKey5); 
    }
  display.setCursor(10, 40);
  display.print("T13: ");// Start at top-left corner
  display.print(data);
  display.display();
  delay (timeBetweenReadings);

  Serial.print("Sensor 14(*C): ");
  data = sensors.getTempC(sensor14);
  Serial.println(data);
  if (data != 85 || data != -127)
    {
      ThingSpeak.writeField(Channel5, (6), data, myWriteAPIKey5); 
    }
  display.setCursor(10, 48);
  display.print("T14: ");// Start at top-left corner
  display.print(data);
  display.display();

  delay (delayForNewReadingCycle);
}

[Christopher Stapels]

We are very happy to hear that you are getting a lot of use out of ThingSpeak, but I am concerned about your described use.

You should take a look at the licensing FAQ

2. May I sign-up for more than one free license?

No. You may only sign up for one free license even if you have multiple MathWorks Accounts.

I am not aware of any changes from our end on April 24. Can you look at the serial monitor and share the output? Is the device sucessfully connecting to the network? What response are you getting from the device when it attempts to write to ThingSpeak?

In your code, I would reccomend using the Thingspeak.setField() workflow for succesive writes to fields in the same channel. Your writes will have the same timestamp, and you will use fewer messages. In the library examples, there are examples for write multiple fields that will show you the correct syntax.

[Chamath Vithanawasam]

My apologies @Christopher Stapels, I have no intention to misuse the free license that Thingspeak offers. The two different accounts belong to me and one other researcher and we are using it for a joint project. The two accounts belong to two different people.

As for the serial monitor output, everything outputs as it did before 24/04/2021. It will first show that the device has connected to the WiFi, and then print each of the data values one by one. For eg.

Potentiometer at channel 1 is at [some value] ([something]%)

This is what really puzzles me, because the device connects to any WiFi I program it to connect and it displays the data on the serial monitor. But as of the 24th of April, absolutely nothing gets uploaded to Thingspeak. I cleared the channel, replaced the API key, created a new channel. Nothing seems to help.

[Christopher Stapels]

Thanks for the clarification, my apologies. The use you describe is acceptable for the license requirements: you are allowed to share a chanenl with a colleage if they provide the API key to you or share the channel privately.

Can you get the response from ThingSpeak?

try this syntax:

ThingSpeak.setField(1, number1);

ThingSpeak.setField(2, number2);

int x = ThingSpeak.writeFields(myChannelNumber, myWriteAPIKey);

if(x == 200){

Serial.println("Channel update successful.");

}

else{

Serial.println("Problem updating channel. HTTP error code " + String(x));

}

[Chamath Vithanawasam]

@Christopher Stapels I was not able to access the room with the setup described in my original post, so I tried your suggested syntax in a simple example, using my mobile phone as a hotspot. It worked and I got 'Channel update successful.'. Perhaps there was something wrong with the WiFi in that room.

May I know why an 'x==200' indicates that the data is succefully uploaded?

[Christopher Stapels]

HTTP communication has a standard list of communication codes. They let you know what the server did with the request you sent. You can see all of them here on wiki, and a ThingSpeak specific list for error codes.(200 not included).

the ThingSpeak library has extra codes in addition to the HTTP ones, they have a negative sign. For example, connectivity troubles may result in a -3XX error.

Here are all the ThingSpeak library return codes.

[Chamath Vithanawasam]

Noted, @Christopher Stapels. Thanks for all your help.