Introduction: Build Your SPIFFS Temperature Logger & Led Clock


Today i am showing you how to build a Offline Browser Temperature & Humidity Graph Viewer from SPIFFS Data.

This Project saves Temp , Hum & Time from I2C DS3231 periodically to Spiffs Flash in three files.

The files are later opened on web browser request and you see a chart.js Line Chart (See Image Below) for all the logged data.

It will have Date Time wise Separate Offline Line Charts of Temp & Hum.

It includes DNS Server so that you can open any website or ip address to view graph after Connecting to AccessPoint "Temperature".

A I2C 7 Segment Led Backpack is connected to show Time (Date & Temp periodically).

The whole program and hardware is tested by me.

I haven't included Spiff Js Data and used the online script, so you have to store it in the Browser Cache Just by Visiting : chart.js tutorial page


I2C 7 Segment 4 Digit Led Backpack

DHT22 / DHT11

Esp8266 Board (Currently D1 Mini)

I2C DS3231 Module

Esp8266 Connected to PC/Laptop Via Serial (Or D1 Mini with cable)

Step 1: Software Libraries & Pinouts...

Software Side:

Arduino 1.6.5 with Esp8266 Addon

7 Segment Esp8266 Library:

Esp8266 I2C Ds3231 Library:

The newer DHT-sensor-library-master Library Requires:

Copy Adafruit_Sensor.h from to


Connect Esp8266 / D1 Mini Pins like this

i2c 7 segment <> D1 Mini / Esp8266



DIO------------------------------------D5 / IO 14

Clk-------------------------------------D0 / IO 16

i2c DS3231 Module <> D1 Mini / Esp8266



SDA-------------------------------------D2 / IO 5

SCL--------------------------------------D1 / IO 4

DHT22/11 <> D1 Mini / Esp8266

By Front Side

Pin 1--------------------------------5V
Pin 2 -------------------------------D6 / IO 12

Pin3 ---Not Used

Pin4 ---------------------------------Gnd

I have Mentioned Esp8266 IO Pinouts Just for Ease of Readers...

Step 2: Program & Testing...

Open Arduino 1.6.5 and Select Esp12 or D1 Mini

Open the Attached Program File

Program it to board.

View Serial. You will see :

HTTP server started


2016/12/24 18:54:30

Let it format SPIFFS for Once Only.

Restart the module (Unplug / Push Reset and Reopen Com Window

, and it will show correct clock (programmed first time to ds3231 )

How to see offline Temp & Hum Data:

Open to cache the chart.js

Connect to "Temperature" open network.

Added DNS Server to * Addresses so you can:

Browse any Website/Page (If you have not assigned DNS Server Manually to PC/ Router)



To See The Beautiful Offline Line Chart.

Refresh to see updated values after some minutes.

The Esp8266 Will Record Temperature & Humidity Time Wise After 1 Minute (Daily) until SPIFF is FULL!