ThingSpeak Communication Library for Arduino

This example demonstrates how to connect an ESP8266 to WiFi and write an incrementing integer to a specific field in a ThingSpeak channel every 20 seconds.

#include <ESP8266WiFi.h>
#include "secrets.h"
#include "ThingSpeak.h"

char ssid[] = SECRET_SSID;
char pass[] = SECRET_PASS;
WiFiClient  client;

unsigned long myChannelNumber = SECRET_CH_ID;
const char * myWriteAPIKey = SECRET_WRITE_APIKEY;

int number = 0;

void setup() {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA); 
  ThingSpeak.begin(client);
}

void loop() {
  if(WiFi.status() != WL_CONNECTED){
    WiFi.begin(ssid, pass);
    while(WiFi.status() != WL_CONNECTED){
      delay(5000);
    }
  }
  
  int x = ThingSpeak.writeField(myChannelNumber, 1, number, myWriteAPIKey);
  if(x == 200){
    Serial.println("Channel update successful.");
  } else {
    Serial.println("Problem updating channel. HTTP error code " + String(x));
  }

  number++;
  if(number > 99) number = 0;
  delay(20000);
}

This example demonstrates reading from both a public channel (using field number) and a private channel (requiring a Read API Key) using an ESP8266.

#include <ESP8266WiFi.h>
#include "secrets.h"
#include "ThingSpeak.h"

char ssid[] = SECRET_SSID;
char pass[] = SECRET_PASS;
WiFiClient  client;

unsigned long weatherStationChannelNumber = SECRET_CH_ID_WEATHER_STATION;
unsigned int temperatureFieldNumber = 4;

unsigned long counterChannelNumber = SECRET_CH_ID_COUNTER;
const char * myCounterReadAPIKey = SECRET_READ_APIKEY_COUNTER;
unsigned int counterFieldNumber = 1; 

void setup() {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA); 
  ThingSpeak.begin(client);
}

void loop() {
  if(WiFi.status() != WL_CONNECTED){
    WiFi.begin(ssid, pass);
    while(WiFi.status() != WL_CONNECTED){
      delay(5000);
    }
  }

  // Read public channel
  float temperatureInF = ThingSpeak.readFloatField(weatherStationChannelNumber, temperatureFieldNumber);
  if(ThingSpeak.getLastReadStatus() == 200){
    Serial.println("Temperature: " + String(temperatureInF));
  }
  
  delay(15000);

  // Read private channel
  long count = ThingSpeak.readLongField(counterChannelNumber, counterFieldNumber, myCounterReadAPIKey);
  if(ThingSpeak.getLastReadStatus() == 200){
    Serial.println("Counter: " + String(count));
  }
  
  delay(15000);
}

Use the read*Field methods to retrieve the latest data from a specific field in a channel. For private channels, you must provide the readAPIKey.

Return Values & Behavior:

• readStringField(): Returns the value as a String. Returns an empty string on error.
• readFloatField(): Returns a float. Returns 0 if the field is text or an error occurs. Note that NAN, INFINITY, and -INFINITY are valid results. Use getLastReadStatus() for error details.
• readLongField(): Returns a long. Returns 0 if the field is text or an error occurs.
• readIntField(): Returns an int. Returns 0 if the field is text or an error occurs. If the value is out of range for an int, the result is undefined.
• readStatus(): Returns the channel status as a String.
• readCreatedAt(): Returns the latest update's timestamp as a String.

String readStringField (channelNumber, field, readAPIKey)
float readFloatField (channelNumber, field, readAPIKey)
long readLongField (channelNumber, field, readAPIKey)
int readIntField (channelNumber, field, readAPIKey)
String readStatus (channelNumber, readAPIKey)
String readCreatedAt (channelNumber, readAPIKey)

After calling readMultipleFields(), use these functions to fetch the locally stored values for a specific field (1-8).

Note: These functions are not available on Arduino Uno due to memory constraints.

• getFieldAsString(field): Returns the value as a String. Returns an empty string on error.
• getFieldAsFloat(field): Returns the value as a float. Returns 0 if the field is text or an error occurs. Note that NAN, INFINITY, and -INFINITY are valid results.
• getFieldAsLong(field): Returns the value as a long. Returns 0 on error.
• getFieldAsInt(field): Returns the value as an int. Returns 0 on error.

If called before readMultipleFields(), these functions return the previously read (old) value.

// Example workflow
int status = readMultipleFields(myChannel, myKey);
if (status == 200) {
    float val = getFieldAsFloat(1);
    int valInt = getFieldAsInt(2);
    String valStr = getFieldAsString(3);
}

Use writeField() to send a single piece of data to a specific field in a ThingSpeak channel.

Signature: int writeField(channelNumber, field, value, writeAPIKey)

Parameters:

• channelNumber (unsigned long): The ID of your ThingSpeak channel.
• field (unsigned int): The field number (1-8) within the channel.
• value: The data to write. Supported types:
  • int (-32,768 to 32,767)
  • long (-2,147,483,648 to 2,147,483,647)
  • float (-999,999,000,000 to 999,999,000,000)
  • String or const char * (UTF8 string, max 255 bytes)
• writeAPIKey (const char *): The Write API Key for your channel.

Returns:

• Returns the HTTP status code. A value of 200 indicates success.

// Example: Writing an integer to field 1
int x = ThingSpeak.writeField(myChannelNumber, 1, number, myWriteAPIKey);
if(x == 200) {
  Serial.println("Channel update successful.");
}