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README.md

ThingSpeak Communication Library for Arduino, ESP8266 and ESP32

This library enables an Arduino or other compatible hardware to write or read data to or from ThingSpeak, an open data platform for the Internet of Things with MATLAB analytics and visualization.

Hardware specific examples are found here. But to give you an idea of usage examples for writing and reading with an ESP8266 are shown below. Complete documentation in also shown below.

ThingSpeak offers free data storage and analysis of time-stamped numeric or alphanumeric data. Users can access ThingSpeak by visiting http://thingspeak.com and creating a ThingSpeak user account.

ThingSpeak stores data in channels. Channels support an unlimited number of timestamped observations (think of these as rows in a spreadsheet). Each channel has up to 8 fields (think of these as columns in a speadsheet). Check out this video for an overview.

Channels may be public, where anyone can see the data, or private, where only the owner and select users can read the data. Each channel has an associated Write API Key that is used to control who can write to a channel. In addition, private channels have one or more Read API Keys to control who can read from private channel. An API Key is not required to read from public channels. Each channel can have up to 8 fields. One field is created by default.

You can visualize and do online analytics of your data on ThingSpeak using the built in version of MATLAB, or use the desktop version of MATLAB to get deeper historical insight. Visit https://www.mathworks.com/hardware-support/thingspeak.html to learn more.

Libraries and examples for Particle devices can be found here: https://github.com/mathworks/thingspeak-particle

Installation

In the Arduino IDE, choose Sketch/Include Library/Manage Libraries. Click the ThingSpeak Library from the list, and click the Install button.

--- or ---

  1. Download the ZIP file (below) to your machine.
  2. In the Arduino IDE, choose Sketch/Include Library/Add Zip Library
  3. Navigate to the ZIP file, and click Open

Compatible Hardware:

  • Arduino/Genuino or compatible using a WiFi Shield
  • Arduino/Genuino or compatible using a WiFi Shield 101 (Use the WiFi101 library version 0.13.0 or older.)
  • Arduino/Genuino or compatible using an Ethernet Shield
  • Arduino/Genuino or compatible using a MKR ETH Shield
  • Arduino MKR1000
  • Arduino MKR1010
  • Arduino VIDOR 4000
  • Arduino GSM 14000
  • Arduino Uno WiFi Rev2
  • Arduino Yún (Rev1 and Rev2)
  • ESP8266 programming directly (tested with SparkFun ESP8266 Thing - Dev Board and NodeMCU 1.0 module)
  • ESP8266 via AT commands
  • ESP32 (tested with SparkFun ESP32 Thing)

Examples

The library includes several examples organized by board type to help you get started. These are accessible in Examples > ThingSpeak menu of the Arduino IDE.

  • ReadField: Reading from a public channel and a private channel on ThingSpeak.
  • WriteSingleField: Writing a value to a single field on ThingSpeak.
  • WriteMultipleFields: Writing values to multiple fields and status in one transaction with ThingSpeak.

Typical Write Example

In this case, write to a field with an ESP8266 with an incrementing number.

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

//----------------  Fill in your credentails   ---------------------
char ssid[] = "MySSID";             // your network SSID (name) 
char pass[] = "MyPassword";         // your network password
unsigned long myChannelNumber = 0;  // Replace the 0 with your channel number
const char * myWriteAPIKey = "";    // Paste your ThingSpeak Write API Key between the quotes 
//------------------------------------------------------------------

WiFiClient  client;

int number = 0;

void setup() {
  //Initialize serial and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  WiFi.mode(WIFI_STA);
  ThingSpeak.begin(client); 
}

void loop() {

  // Connect or reconnect to WiFi
  if(WiFi.status() != WL_CONNECTED){
    Serial.print("Attempting to connect to SSID: ");
    Serial.println(SECRET_SSID);
    while(WiFi.status() != WL_CONNECTED){
      WiFi.begin(ssid, pass);
      Serial.print(".");
      delay(5000);     
    } 
    Serial.println("\nConnected.");
  }
  
  // Write to ThingSpeak. There are up to 8 fields in a channel, allowing you to store up to 8 different
  // pieces of information in a channel.  Here, we write to field 1.
  int x = ThingSpeak.writeField(myChannelNumber, 1, number, myWriteAPIKey);
  
  // Check the return code
  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); // Wait 20 seconds before sending a new value
}

Typical Read Example

In this case, read from a public channel and a private channel with an ESP8266. The public channel is the temperature(F) at MathWorks headquarters. The private channel is a counter that increments.

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

//----------------  Fill in your credentails   ---------------------
char ssid[] = "MySSID";     // your network SSID (name) 
char pass[] = "MyPassword"; // your network password
//------------------------------------------------------------------

WiFiClient  client;

unsigned long weatherStationChannelNumber = 12397;
unsigned int temperatureFieldNumber = 4;

unsigned long counterChannelNumber = 298725;
const char * myCounterReadAPIKey = "SODG0O2UZVGKWAWG";
unsigned int counterFieldNumber = 1; 

void setup() {
 //Initialize serial and wait for port to open:
 Serial.begin(9600);
 while (!Serial) {
   ; // wait for serial port to connect. Needed for native USB port only
 }

 WiFi.mode(WIFI_STA);  
 ThingSpeak.begin(client);
}

void loop() {

 int statusCode = 0;
 
 // Connect or reconnect to WiFi
 if(WiFi.status() != WL_CONNECTED){
   Serial.print("Attempting to connect to SSID: ");
   Serial.println(SECRET_SSID);
   while(WiFi.status() != WL_CONNECTED){
     WiFi.begin(ssid, pass);
     Serial.print(".");
     delay(5000);     
   } 
   Serial.println("\nConnected");
 }

 // Read in field 4 of the public channel recording the temperature
 float temperatureInF = ThingSpeak.readFloatField(weatherStationChannelNumber, temperatureFieldNumber);  

 // Check the status of the read operation to see if it was successful
 statusCode = ThingSpeak.getLastReadStatus();
 if(statusCode == 200){
   Serial.println("Temperature at MathWorks HQ: " + String(temperatureInF) + " deg F");
 }
 else{
   Serial.println("Problem reading channel. HTTP error code " + String(statusCode)); 
 }
 
 delay(15000); // No need to read the temperature too often.

 // Read in field 1 of the private channel which is a counter  
 long count = ThingSpeak.readLongField(counterChannelNumber, counterFieldNumber, myCounterReadAPIKey);  

  // Check the status of the read operation to see if it was successful
 statusCode = ThingSpeak.getLastReadStatus();
 if(statusCode == 200){
   Serial.println("Counter: " + String(count));
 }
 else{
   Serial.println("Problem reading channel. HTTP error code " + String(statusCode)); 
 }
 
 delay(15000); // No need to read the counter too often.
 
}

Documentation

begin

Initializes the ThingSpeak library and network settings.

bool begin (client) // defaults to ThingSpeak.com
bool begin (client, port)
Parameter Type Description
client Client & TCPClient created earlier in the sketch
port unsigned int Port number to use with a custom install of ThingSpeak

Returns

Always returns true. This does not validate the information passed in, or generate any calls to ThingSpeak.

writeField

Write a value to a single field in a ThingSpeak channel.

int writeField(channelNumber, field, value, writeAPIKey)
Parameter Type Description
channelNumber unsigned long Channel number
field unsigned int Field number (1-8) within the channel to write to.
value int Integer value (from -32,768 to 32,767) to write.
long Long value (from -2,147,483,648 to 2,147,483,647) to write.
float Floating point value (from -999999000000 to 999999000000) to write.
String String to write (UTF8 string). ThingSpeak limits this field to 255 bytes.
const char * Character array (zero terminated) to write (UTF8). ThingSpeak limits this field to 255 bytes.
writeAPIKey const char * Write API key associated with the channel. If you share code with others, do not share this key

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

Remarks

Special characters will be automatically encoded by this method. See the note regarding special characters below.

writeFields

Write a multi-field update. Call setField() for each of the fields you want to write first.

int writeFields (channelNumber, writeAPIKey)	
Parameter Type Description
channelNumber unsigned long Channel number
writeAPIKey const char * Write API key associated with the channel. If you share code with others, do not share this key

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

Remarks

Special characters will be automatically encoded by this method. See the note regarding special characters below.

writeRaw

Write a raw POST to a ThingSpeak channel.

int writeRaw (channelNumber, postMessage, writeAPIKey)	
Parameter Type Description
channelNumber unsigned long Channel number
postMessage const char * Raw URL to write to ThingSpeak as a String. See the documentation at https://thingspeak.com/docs/channels#update_feed.
String Raw URL to write to ThingSpeak as a character array (zero terminated). See the documentation at https://thingspeak.com/docs/channels#update_feed.
writeAPIKey const char * Write API key associated with the channel. If you share code with others, do not share this key

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

Remarks

This method will not encode special characters in the post message. Use '%XX' URL encoding to send special characters. See the note regarding special characters below.

setField

Set the value of a single field that will be part of a multi-field update.

int setField (field, value)
Parameter Type Description
field unsigned int Field number (1-8) within the channel to set
value int Integer value (from -32,768 to 32,767) to write.
long Long value (from -2,147,483,648 to 2,147,483,647) to write.
float Floating point value (from -999999000000 to 999999000000) to write.
String String to write (UTF8 string). ThingSpeak limits this field to 255 bytes.
const char * Character array (zero terminated) to write (UTF8). ThingSpeak limits this field to 255 bytes.

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

setStatus

Set the status of a multi-field update. Use status to provide additonal details when writing a channel update. Additionally, status can be used by the ThingTweet App to send a message to Twitter.

int setStatus (status)	
Parameter Type Description
status const char * String to write (UTF8). ThingSpeak limits this to 255 bytes.
String const character array (zero terminated). ThingSpeak limits this to 255 bytes.

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

setLatitude

Set the latitude of a multi-field update.

int setLatitude	(latitude)	
Parameter Type Description
latitude float Latitude of the measurement (degrees N, use negative values for degrees S)

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

setLongitude

Set the longitude of a multi-field update.

int setLongitude (longitude)	
Parameter Type Description
longitude float Longitude of the measurement (degrees E, use negative values for degrees W)

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

setElevation

Set the elevation of a multi-field update.

int setElevation (elevation)	
Parameter Type Description
elevation float Elevation of the measurement (meters above sea level)

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

setCreatedAt

Set the created-at date of a multi-field update. The timestamp string must be in the ISO 8601 format. Example "2017-01-12 13:22:54"

int setCreatedAt (createdAt)
Parameter Type Description
createdAt String Desired timestamp to be included with the channel update as a String.
const char * Desired timestamp to be included with the channel update as a character array (zero terminated).

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

Remarks

Timezones can be set using the timezone hour offset parameter. For example, a timestamp for Eastern Standard Time is: "2017-01-12 13:22:54-05". If no timezone hour offset parameter is used, UTC time is assumed.

setTwitterTweet

Set the Twitter account and message to use for an update to be tweeted.

int setTwitterTweet	(twitter, tweet)	
Parameter Type Description
twitter String Twitter account name as a String.
const char * Twitter account name as a character array (zero terminated).
tweet String Twitter message as a String (UTF-8) limited to 140 character.
const char * Twitter message as a character array (zero terminated) limited to 140 character.

Returns

HTTP status code of 200 if successful. See Return Codes below for other possible return values.

Remarks

Prior to using this feature, a twitter account must be linked to your ThingSpeak account. To link your twitter account. login to ThingSpeak and go to Apps -> ThingTweet and click Link Twitter Account.

readStringField

Read the latest string from a channel. Include the readAPIKey to read a private channel.

String readStringField (channelNumber, field, readAPIKey)	
String readStringField (channelNumber, field)	
Parameter Type Description
channelNumber unsigned long Channel number
field unsigned int Field number (1-8) within the channel to read from.
readAPIKey const char * Read API key associated with the channel. If you share code with others, do not share this key

Returns

Value read (UTF8 string), or empty string if there is an error.

readFloatField

Read the latest float from a channel. Include the readAPIKey to read a private channel.

float readFloatField (channelNumber, field, readAPIKey)	
float readFloatField (channelNumber, field)	
Parameter Type Description
channelNumber unsigned long Channel number
field unsigned int Field number (1-8) within the channel to read from.
readAPIKey const char * Read API key associated with the channel. If you share code with others, do not share this key

Returns

Value read, or 0 if the field is text or there is an error. Use getLastReadStatus() to get more specific information. Note that NAN, INFINITY, and -INFINITY are valid results.

readLongField

Read the latest long from a channel. Include the readAPIKey to read a private channel.

long readLongField (channelNumber, field, readAPIKey)	
long readLongField (channelNumber, field)	
Parameter Type Description
channelNumber unsigned long Channel number
field unsigned int Field number (1-8) within the channel to read from.
readAPIKey const char * Read API key associated with the channel. If you share code with others, do not share this key

Returns

Value read, or 0 if the field is text or there is an error. Use getLastReadStatus() to get more specific information.

readIntField

Read the latest int from a channel. Include the readAPIKey to read a private channel.

int readIntField (channelNumber, field, readAPIKey)		
int readIntField (channelNumber, field)		
Parameter Type Description
channelNumber unsigned long Channel number
field unsigned int Field number (1-8) within the channel to read from.
readAPIKey const char * Read API key associated with the channel. If you share code with others, do not share this key

Returns

Value read, or 0 if the field is text or there is an error. Use getLastReadStatus() to get more specific information. If the value returned is out of range for an int, the result is undefined.

readStatus

Read the latest status from a channel. Include the readAPIKey to read a private channel.

String readStatus (channelNumber, readAPIKey)	
String readStatus (channelNumber)
Parameter Type Description
channelNumber unsigned long Channel number
readAPIKey const char * Read API key associated with the channel. If you share code with others, do not share this key

Returns

Returns the status field as a String.

String readCreatedAt()

Read the created-at timestamp associated with the latest update to a channel. Include the readAPIKey to read a private channel.

String readCreatedAt (channelNumber, readAPIKey)
String readCreatedAt (channelNumber)	

| channelNumber | unsigned long | Channel number | | readAPIKey | const char * | Read API key associated with the channel. If you share code with others, do not share this key |

Returns

Returns the created-at timestamp as a String.

readRaw

Read a raw response from a channel. Include the readAPIKey to read a private channel.

String readRaw (channelNumber, URLSuffix, readAPIKey)	
String readRaw	(channelNumber, URLSuffix)
Parameter Type Description
channelNumber unsigned long Channel number
URLSuffix String Raw URL to write to ThingSpeak as a String. See the documentation at https://thingspeak.com/docs/channels#get_feed
readAPIKey const char * Read API key associated with the channel. If you share code with others, do not share this key.

Returns

Returns the raw response from a HTTP request as a String.

getLastReadStatus

Get the status of the previous read.

int getLastReadStatus ()	

Returns

See Return Codes below for other possible return values.

Return Codes

Value Meaning
200 OK / Success
404 Incorrect API key (or invalid ThingSpeak server address)
-101 Value is out of range or string is too long (> 255 characters)
-201 Invalid field number specified
-210 setField() was not called before writeFields()
-301 Failed to connect to ThingSpeak
-302 Unexpected failure during write to ThingSpeak
-303 Unable to parse response
-304 Timeout waiting for server to respond
-401 Point was not inserted (most probable cause is the rate limit of once every 15 seconds)
0 Other error

Special Characters

Some characters require '%XX' style URL encoding before sending to ThingSpeak. The writeField() and writeFields() methods will perform the encoding automatically. The writeRaw() method will not.

Character Encoding
" %22
% %25
& %26
+ %2B
; %3B

Control characters, ASCII values 0 though 31, are not accepted by ThingSpeak and will be ignored. Extended ASCII characters with values above 127 will also be ignored.

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