Source: https://mokxi.com/libraries/thingspeak Updated: 2026-11-02 Libraries / Network Arduino library · Network # ThingSpeak: log sensor data to a channel from an ESP32 or ESP8266 ThingSpeak is MathWorks’ IoT service: a channel holds up to eight numbered fields, each a time series, and the website charts them. The ThingSpeak library turns each of its calls into one HTTP request to api.thingspeak.com, so a sketch needs only a channel number, a write API key and a WiFiClient to log readings. Open the example in the editor See the calls Built in on Mokxi: #include and it builds, with nothing to install. Free, and no account needed. ## What ThingSpeak does There are two ways to write. writeField() sends one value to one field. For several readings at once, setField() each value first and then call writeFields() once: the channel gets one entry with all of them, which matters because a free account accepts one write every 15 seconds. Every call returns a code, 200 when the server took it. Anything else tells you what went wrong, from -301 for a connection that failed to -401 for a write the server refused, usually for coming too soon after the last one. Library Manager name | ThingSpeak Author | MathWorks Include | #include Boards | ESP32-C3, ESP32-C6, Seeed XIAO ESP32-C3, ESP32-C3 SuperMini, Seeed XIAO ESP32-C6, ESP32 DevKit, ESP32-DevKitC V4, LOLIN32 Lite, Wemos D1 R32, Cheap Yellow Display, TTGO T-Display, ESP32-S3-DevKitC-1, Seeed XIAO ESP32-S3, Arduino Nano ESP32, ESP8266 NodeMCU, Raspberry Pi Pico W, Arduino Uno R4 WiFi In the simulator | Runs, with a gap the note below names. ## Install it It builds on ESP32-C3, ESP32-C6, Seeed XIAO ESP32-C3, ESP32-C3 SuperMini, Seeed XIAO ESP32-C6, ESP32 DevKit, ESP32-DevKitC V4, LOLIN32 Lite, Wemos D1 R32, Cheap Yellow Display, TTGO T-Display, ESP32-S3-DevKitC-1, Seeed XIAO ESP32-S3, Arduino Nano ESP32, ESP8266 NodeMCU, Raspberry Pi Pico W, Arduino Uno R4 WiFi. In Mokxi it is built in: #include and the sketch compiles, with no download, no zip and no Library Manager. On a real board, install "ThingSpeak" by MathWorks from the Arduino IDE’s Library Manager (Sketch, Include Library, Manage Libraries), or add ThingSpeak to lib_deps in PlatformIO. Mokxi follows the calls of release 2.1.1, so a sketch written here builds there too. What to know in the simulator: api.thingspeak.com is outside the simulated network, so calls return -301 there. #define THINGSPEAK_URL "api.mokxi" before the include sends them to the Cloud panel’s API lab instead. ESP32-C3 · ESP32-C6 · Seeed XIAO ESP32-C3 · ESP32-C3 SuperMini · Seeed XIAO ESP32-C6 · ESP32 DevKit · ESP32-DevKitC V4 · LOLIN32 Lite · Wemos D1 R32 · Cheap Yellow Display · TTGO T-Display · ESP32-S3-DevKitC-1 · Seeed XIAO ESP32-S3 · Arduino Nano ESP32 · ESP8266 NodeMCU · Raspberry Pi Pico W · Arduino Uno R4 WiFi ## The calls you will use In the order a sketch meets them. ### ThingSpeak.begin(client) Gives the library the network client to send through, normally a WiFiClient declared at the top of the sketch. Call it once in setup(). ### ThingSpeak.writeField(myChannelNumber, 1, temperature, myWriteAPIKey) Writes one value to field 1 and returns 200 on success. The value may be an int, a long, a float or a String. ### ThingSpeak.setField(2, humidity) Stages a value for field 2 without sending it. Stage as many fields as you have, then send them together. ### ThingSpeak.setStatus("door open") Stages the entry’s status text, shown with the entry on the channel page. ### ThingSpeak.writeFields(myChannelNumber, myWriteAPIKey) Sends every staged field as one channel entry, and clears them for the next write. ### ThingSpeak.readFloatField(myChannelNumber, 1, myReadAPIKey) Reads the newest value of a field. Leave out the read key for a public channel. readIntField() and readStringField() read other types. ### ThingSpeak.getLastReadStatus() The code of the last read, 200 when it worked. A read returns 0 on failure, so check this to tell a real zero from an error. ## Example: A ThingSpeak write, and why it fails here On the ESP32-C3-DevKitM-1. It runs in the browser exactly as printed. sketch.ino · ESP32-C3-DevKitM-1 Open it in the editor, wired and ready to run ## Common errors and how to fix them ### Problem updating channel. HTTP error code -401 The server did not insert the point, almost always because writes came faster than once every 15 seconds on a free account. Wait at least 15 seconds between writes, and combine readings into one writeFields() call. ### HTTP error code -301 The board could not connect to the server: no WiFi, a wrong network client, or a WiFiClientSecure the library cannot use for plain HTTP. In Mokxi, add #define THINGSPEAK_URL "api.mokxi" above the include to send the calls to the Cloud panel’s API lab. ### HTTP error code 400 or -210 400 means the write API key is wrong, often the read key pasted by mistake. -210 means writeFields() was called with nothing staged: call setField() for at least one field first. ## Keep going ### Learn - ESP32 HTTP GET Request: Fetch the Weather as JSON - ESP32 IoT Projects for Final Year Students ### More network libraries - PubSubClient - MQTT - Blynk - WiFiManager - WiFi, HTTPClient and WebServer (ESP32 core) Every built-in library · Open the editor ## Try ThingSpeak without installing anything Open the example, change the sketch, and keep your version in a free account. Start building free Open the editor