Geekcreit® ESP8266 IoT Development Board + DHT11 Temperature and Humidity Sensor + Yellow Blue OLED Display
Geekcreit ESP8266 IoT Dev Board Schematic
The Geekcreit® ESP8266 IoT Development Board consist of :
- IoT main board with ESP8266 Wifi module (ESP-12F)
- 3 pin interface for DHT11 Temperature and Humidity sensor (included)
- 4 pin I2C interface for 0.96" Yellow/Blue OLED module (included)
- micro USB interface for power and communicationv
| Header | No | Pin | Description |
|---|---|---|---|
| Micro USB | |||
| P1 | 1 | VCC | VCC 5V -> LED1 power (red) |
| P1 | 2 | D- | USB Data - |
| P1 | 3 | D+ | USB Data + |
| P1 | 4 | ID | USB ID (NC) |
| P1 | 5 | GND | Ground |
| OLED | |||
| P2 | 1 | 3V3 | VCC 3.3V |
| P2 | 2 | GND | Ground |
| P2 | 3 | SCL | GPIO 14 -> I2C clock pin OLED |
| P2 | 4 | SDA | GPIO 2 -> I2C data pin OLED |
| ESP8266 left | |||
| P3 | 1 | GND | Ground |
| P3 | 2 | 5V | VCC 5V |
| P3 | 3 | ADC | Analog to digital convertor |
| P3 | 4 | IO16 | GPIO 16 |
| P3 | 5 | IO14 | GPIO 14 -> I2C clock pin OLED |
| P3 | 6 | IO12 | GPIO 12 |
| P3 | 7 | IO13 | GPIO 13 |
| ESP8266 right | |||
| P4 | 1 | GND | Ground |
| P4 | 2 | 3V3 | VCC 3.3V |
| P4 | 3 | TXD | UART0_TXD, GPIO1 |
| P4 | 4 | RXD | UART0_RXD, GPIO3 |
| P4 | 5 | IO5 | GPIO 5 -> DHT11 data pin |
| P4 | 6 | IO4 | GPIO 4 -> LED2 signal (green) |
| P4 | 7 | IO0 | GPIO 0 |
| P4 | 8 | IO2 | GPIO 2 -> I2C data pin OLED |
| P4 | 9 | IO15 | GPIO 15 |
| DHT11 | |||
| P5 | 1 | GND | Ground |
| P5 | 2 | DAT | GPIO 5 -> DHT11 data pin |
| P5 | 3 | 3V3 | VCC 3.3V |
The dev board can work in these modes :
| Mode | GPIO 0 | GPIO 2 | GPIO 15 |
|---|---|---|---|
| Program operation | 1 | 1 | 0 |
| Serial download | 0 | 1 | 0 |
The code will show the following information on the OLED display:
- Day of week
- Date
- Time
- Temperature (°C)
- Humidity (%)
- Download the latest Micropython firmware
- Install the firmware onto the IoT Dev Board
The sourcecode consists of the following functions:
- updateRTC : The internal RTC of the ESP8266 is accurate enough to be used to get the date and time to be displayed. As the module contains no battery, the current date and time is adjusted to UTC by calling an NTP server on the Internet via Wifi. Then the RTC is updated to the correct localtime according to the Timezone and Daylight Saving Time options. This process is executed every 2 hours.
- measureDHT : The DHT11 temperature and humidity is measured every 5 seconds.
- refreshOLED : The OLED display with day of week, date, time, temperature and humidity is refreshed every 15 seconds.
Due to the different intervals of the 3 main functions of the program, an asynchronous approch was used when coding (module asyncio)
These are the modules that were used:
| Module | Description | Installation |
|---|---|---|
| machine | hardware related functions | (builtin) |
| network | network configuration | (builtin) |
| utime | time related functions | (builtin) |
| ntptime | synchronize RTC with ntp | (builtin) |
| dht | functions for DHTxx sensors | (builtin) |
| ssd1306 | functions for oled displays | (builtin) |
| uasyncio | asynchronous I/O scheduler | (builtin) |
| writer_minimal | writer for custom fonts on ssd1306 display | Peter Hinch github |
| freesans20 | custom font 20px for ssd1306 display | Peter Hinch github |
| freesans30 | custom font 30px for ssd1306 display | Peter Hinch github |
If you get Memory allocation failed errors during execution of the Python script, this is probably caused by the heap memory being too fragmented to load the large freesans font files. An easy solution is to cross compile these files with the MicroPython cross compiler. Then upload the much smaller .mpy files to your ESP8266 board and be sure to delete the .py versions. This will get rid of the memory errors.
Upload the sourcecode as boot.py to the IoT Dev Board and press the reset button. The following is shown on the OLED display:
- Download the latest Arduino IDE for you OS and install it.
- Start the Arduino IDE, go to File > Preferences and enter http://arduino.esp8266.com/stable/package_esp8266com_index.json into the “Additional Boards Manager URLs” field
- Go to Tools > Board > Boards Manager…
- Search for ESP8266 and press install button for the ESP8266 by ESP8266 Community boards.
The sourcecode consists of the following functions:
- setup : contains initialisation code for Serial Monitor, DHT11 sensor, I2C and OLED display. It also connects to your Wi-Fi network, initialises the NTP client and sets the Daylight Saving Time offset.
- loop : contains code for scheduling connection to the ntp server to adjust the current date and time, measurement of temperature and humidity with the DHT11 sensor and refreshing the OLED display.
- updateRTC : The internal RTC of the ESP8266 is accurate enough to be used to get the date and time to be displayed. As the module contains no battery, the current date and time is adjusted by calling an NTP server on the Internet via Wifi. This process is executed every 2 hours to adjust the RTC.
- measureDHT : The DHT11 temperature and humidity is measured every 5 seconds.
- refreshOLED : The OLED display with day of week, date, time, temperature and humidity is refreshed every second.
Due to the different intervals of the 3 main functions of the program, a non blocking delay approch was implemented using millis()
The code uses the following libraries:
| Library | Author | Installation |
|---|---|---|
| Wire | Arduino | (builtin) |
| Adafruit GFX Library | Adafruit | Sketch > Use Library > Library Manager |
| Adafruit SSD1306 | Adafruit | Sketch > Use Library > Library Manager |
| Adafruit Unified Sensor | Adafruit | Sketch > Use Library > Library Manager |
| DHT sensor library | Adafruit | Sketch > Use Library > Library Manager |
| WifiManager | Tzapu,Tablatronix | Sketch > Use Library > Library Manager |
| NtpClient | Fabrice Weinberg | Sketch > Use Library > Library Manager |
| Time | Paul Stoffregen | Download zip from https://github.com/PaulStoffregen/Time then Sketch > Use Library > Add Zip Library |
Select Tools > Board > ESP8266 Boards > Generic ESP8266 Module Select Tools > Port > (usb port of IoT module) Upload the sourcecode to the IoT Dev Board by pressing the upload button. After upload the board is reset and the following is shown on the OLED display:
