Example of reading four probes via Adafruit IO, and displaying in rotation on a display.

probeDisplay.ino

/**
*** Probes & Data storage
**/

AdafruitIO_Feed *probe1 = io.feed("probe_one");
AdafruitIO_Feed *probe2 = io.feed("probe_two");
AdafruitIO_Feed *probe3 = io.feed("probe_three");
AdafruitIO_Feed *probe4 = io.feed("probe_four");

const int numberOfProbes = 4;

float readings[numberOfProbes];
bool readingValid[numberOfProbes];
uint32_t readingMillis[numberOfProbes];

void handleProbe(int probeNumber, AdafruitIO_Data *data) {
  readings[probeNumber] = data->toFloat();
  readingsValid[probeNumber] = true;
  readingsMillis[probeNumber] = millis();
}

void handleProbe1(AdafruitIO_Data *data) {
  handleProbe(0, data); // Note index starting from zero
}
void handleProbe2(AdafruitIO_Data *data) {
  handleProbe(1, data);
}
void handleProbe3(AdafruitIO_Data *data) {
  handleProbe(2, data);
}
void handleProbe4(AdafruitIO_Data *data) {
  handleProbe(3, data);
}

void probesStart() {
  Serial.print("Connecting to Adafruit IO");
  io.connect();

  probe1->onMessage(handleProbe1);
  probe2->onMessage(handleProbe2);
  probe3->onMessage(handleProbe3);
  probe4->onMessage(handleProbe4);

  while(io.status() < AIO_CONNECTED) {
    Serial.print(".");
    delay(500);
  }
  Serial.println();
  Serial.println(io.statusText());

  // I'm not sure these four lines are needed at all
  probe1->get();
  probe2->get();
  probe3->get();
  probe4->get();
}

void probesRun() {
  io.run();
}


/**
*** Display of Probe data
**/

const char* probeNames[numberOfProbes] {
  "DAY",
  "Bott",
  "Foo",
  "Bar"
};

const uint32_t screenRotationMillis = 2000;  // 2 seconds between screens
const uint32_t staleDataMillis = 10000;      // data considered old after 10 sec

void display(uint32_t now, int probeNumber) {
  matrix.setRotation(2);
  matrix.clearScreen();
  matrix.setCursor(0, 0);
  matrix.println(probeNames[probeNumber]);

  if (readingValid[probeNumber]) {
    matrix.print(readings[probeNumber]);
    matrix.print(" F");

    if (now - readingMillis[probeNumber] < staleDataMillis) {
      matrix.print(" old");
    }
  } else {
    matrix.print("--"); // no reading yet
  }
  matrix.writeScreen();
}

void displayRun() {
  static uint32_t nextDisplayTime = 0;
  static int nextProbeToDisplay = 0;

  uint32_t now = millis();
  if (now > nextDisplayTime) {
    display(now, nextProbeToDisplay);
    nextDisplayTime = now + screenRotationMillis;
    nextProbeToDisplay = (nextProbeToDisplay + 1) % numberOfProbes;
  }
}

/**
*** Main code
**/

void setup() {
  Serial.begin(115200);
  while(! Serial);  // wait for serial monitor to open

  probesStart();
}

void loop() {
  probesRun();
  displayRun();
}