• Arduino mega 2560 or other development board with enough RAM and flash
• Ethernet shield
• BME280 using I2C
• OLED 128x64 screen using I2C
• Data is uploaded to ThingSpeak using MQTT 3.1.1 protocol

• The webserver uses Base64 authentication, this is a basic security for your account.
  Base64 encoding is reversible. Do not show your encoding online.
  Arduino mega does not support TLS (https). If you are connecting from public networks your webserver credentials may be exposed.
• The code uses milis() instead of delay()
• MQTT protocol should be faster, more precise and use less energy than Rest API
• The index htm file is developed by neih10. I just updated the ThingSpeak api.

1 2 3 4

• Connect the pins as in the following table (you will need to join together the VCC with VIN and both SCL and SDA)

• Download the index.htm file and place it on the SD card outside of any folder. The card must be formatted as FAT16 or FAT32

  • Edit the following lines in the index.htm file:

  channelKeys.push({channelNumber:871658, name:'Your channel name',key:'NP1I3KHAW44KY0Q3',
                fieldList:[{field:1,axis:'T'},{field:2,axis:'H'},{field:3,axis:'P'},{field:4,axis:'I'}]});

  The key is your Read API key.

• Install the required libraries:

  • Adafruit BME280 Library
  • Adafruit Unified Sensor
  • Adafruit SSD1306
  • Base64
  • Ethernet
  • MQTT
  • SD

• If you use PlatformIO place the following lines in your platformio.ini file and all required libraries will be installed.

lib_deps = 
    arduino-libraries/Ethernet @ ^2.0.0
    adafruit/Adafruit BME280 Library @ ^2.2.2
    arduino-libraries/SD @ ^1.2.4
    agdl/Base64 @ ^1.0.0
    adafruit/Adafruit GFX Library @ ^1.10.14
	adafruit/Adafruit SSD1306 @ ^2.5.3
    adafruit/Adafruit BusIO @ ^1.5.0
    256dpi/MQTT @ ^2.5.0

• You will need to overwrite the mqtt_secrets.h with the ones obtained from ThinkgSpeak, Devices, MQTT
• Edit the arduino code with your login details and channel information:

long channelID = 871658;                    // Change to your channel ID.

char userAndPassword[] = "admin:admin";

My W5100 ethernet shield replica had a problem that it would not turn on when plugged in to a wall socket (5v or 9v). This issue seems to be included also in the arduino ethernet shield documentation -> Previous revisions of the shield were not compatible with the Mega and need to be manually reset after power-up.
I read online that a 0.1μF (100nF) capacitor soldered on the reset button will make the ethernet shield turn on when connected to a power socket.
It did but at a cost, now the ethernet shield is no longer resettable from the computer's USB port, meaning I have to push the reset button exactly when a new sketch is uploaded. ¯_(ツ)_/¯