This time it will show how to read data from nodeMCU, WemOS, or similar via the Internet – The first example I will use is the temperature reading from the sensor connected to ESP on demand – YOu click refresh and immediately You got actual temperature, humidity, and pressure displayed at webPage

The second example is reading temperature, pressure, and humidity periodically and store it at the database, so You can later display some chart with historical data

You can watch all steps in youtube



Temperature pressure and humidity on demand



Access to the entire mechanism will be outside the local network, i.e. it will not be a problem to read the temperature from the phone mobile in the bus.

To read the temperature we will create synchronous communication, after sending a message to our ESP in response we will get temperature, humidity and pressure.

In general, to create this type of scenario, we must have access to our arduino from outside the local network – there are several solutions I will show you how to do it with

What we want to achieve

A website with this appearance:

After loading the page, we display the current temperature, pressure and humidity, and of course the data are reload after clicking the Refresh button.


  • nodeMCU or WemOS
  • GY-BME280 – as a thermometer, a hygrometer and a pressure meter in one


Connections configuring

Before we return to our arduino, let’s register our account in the system and create a token – the tasks described above.

  •  open app
  • Sign Up tab
  • you do not give your email so it is not possible to retrieve your password – you must remember it
  • Click SignUp the system will login us immediately

Creating a token

Using the token added to the arduino program, arduino will be connected to our account.

  • Go to the tab Tokens on the left
  • Click New Token, complete the name (no matter what you type) and click OK
  • [3] this is the only field you fill – the name of the token is only for us, it is not used anywhere except displaying the token in the token list.
  • The token will be created:
  • in my case token is “~267_ZxoWtJ)0ph&2c” it can be copied by clicking on the blue icon


Program for arduino

needed libraries:

  • WebSockets by Markus Sattler
  • ArduinoHttpClient by Arduino
  • ESP8266WiFi by Iven Grokhotkov
  • SparkFun BME280 by SparkFun Electronics
  • RemoteMe libraries by


Program for arduino can be copy from this link

I think that the program itself is quite readable, and the most important function of onUserSyncMessage I described below . Of course, we have to supplement our constants:

In addition, description of the operation at the bottom of the article

Upload arduino program to device. After arduino launch in the Devices tab, our ESP will appear:


Now it’s time to create a website that will connect to our ESP and show the datas.

In the “Devices” tab, select the New button and then “New WebPage”

  • We filled inputs as on the screen. Information what each field meansa you can find here.
  • Now, let’s upload three files to our website.
    • Files to upload index.html, script.js and styles.css are located here
    • The easiest way is to simply drag files from github to our website, shown on the video

  • Opening of the website: click on the index.html file and select the Open in New Tab option. On the new tab will appear our website where after clicking Refresh the temperature, pressure and humidity will change to the current one.

How does it work.

Most important part of code is in the script.js file and in the arduino program. Let us discuss the following fragments:


standard settings. The program immediately connects and registers to the application.

Reference to the function

the function itself looks like this:

so after correct connection with, the program reads the data. The same readDataNow () function is called after clicking the “Refresh” button.

Let’s see what the readDataNow () function does:

it sends the data to our ESP (that’s why you need the temperatureArduinoDeviceId which will indicate the ID (address of our ESP at our example it is 204) as data we send empty table: [], and after the response  come the onResponse function should be called.

Let’s move to program on ESP and see how we handle incoming synchronous messages


the above function will be called when a message arrives from script.js parameters:

  • senderDeviceId – id of our website
  • dataSize – data size of data (at our case its 0 becasue we sent empty array at script.js)
  • data -data from websote (at our case there is nothing here)
  • returnDataSize – here we will enter how many bytes we will send as the answer – we send 12 because we have three readings, and each is a  float number that has 4 bytes
  • returnData – here we write return data

  • using the putFloat function,we  enter three readings in the output table one by one . So after leaving the function, we have an array of bytes where the following numbers are written: temperature, pressure and humidity.

Let’s go back to the script.js file and read these values:


with the popFloat32 pop function, we collect three float numbers one by one and after proper formatting, we display with jquery to the appropriate elements.


Temperature pressure and humidity saved on the server and displayed on the chart

This time we dont want to read the temperatures on demand but save the readings from time to time (in the example 5 minutes intervals ) to the server and see the data on the chart

How does it work

ESP from time to time wakes up from deepSleep mode, reads data from GY-BME280 and saves them to the server, then again fall asleep and wake up sends data, and so on.

Of course, you do not need your own database – provides functions to write data to the cloud – and provides API to read them

The chart we get:


Almost identical as in the project for reading on demand, the difference is the green wire – it allows you to self-wakeup the ESP.

Source code


strona internetowa

Just upload to and our arduino . Everything in the same way as in the previous example.

Description of the most interesting code parts


data reading from BMY280:

We make 9 measurements in a 100ms interval, then sort them, send medians to the server – it will allow you to get rid of wrong data – sometimes our sensor returns strange values

and send them to the server, each data is sotred at diffrent data series (1,2,3) and time is rounded to 5minutes – it will helps draw nicer chart

after the measurements ESP falls asleep for 4 minutes



The most interesting part is receiving data and display them on the chart.

applications provide our data under the link

(documentation of the entire REST Api app is  here   )

URL will returns us data for series which was provided in {SERIES ids}  time will be formatting using  {FORMAT} and data will be from [ {FROM} – {TO} [period.  Data are return as json

in our example, javascript will generate a link:

data are reads for one day back. You can easy change it

Let’s check what I find under the given link (I limited the time to 20 minutes)

“dataSeriesId” is id of our data series so under dataseriesId:1 will be temperature becasuse at arduino we have

and first function argument means dataseries 1

becasue in the link we have 1,2,3 as series ID , all series are returned all together

Then download jeson is displayed using  plotly :

To see this chart You have to open index.html excatly as You did at previous example


Whole function and api documentation You can find here ,