Weather Station with PIC18F46K22 and BME280 Sensor | mikroC Projects

This post shows how to build a weather station using PIC18F46K22 microcontroller and BME280 barometric pressure, temperature and humidity sensor.
The PIC18F46K22 MCU reads temperature & humidity & pressure values from the BME280 sensor and print them (respectively in °C & RH% & hPa) on SSD1306 OLED display (128×64 pixel).
MikroC PRO for PIC compiler is used in this project.

In this project the SSD1306 OLED is configured to work in I2C mode, make sure that your display is configured to work in I2C mode, some displays need jumper placing or some soldering.

To see how to interface PIC18F46K22 MCU with SSD1306 OLED display (I2C mode), visit this topic:
Interfacing PIC18F46K22 with SSD1306 OLED display | mikroC Projects

and to see how to interface PIC microcontroller with BME280 sensor using mikroC PRO for PIC compiler, take a look at this project:
PIC MCU with BME280 pressure, temperature and humidity sensor | mikroC Projects

Hardware Required:

  • PIC18F46K22 microcontroller   —->  datasheet
  • SSD1306 OLED display
  • BME280 sensor module (with built-in 3.3V regulator and level shifter)  —->  BME280 datasheet
  • 5V source
  • Breadboard
  • Jumper wires

PIC18F46K22 with SSD1306 OLED and BME280 sensor circuit:
The image below shows project circuit diagram.

Hint:
The BME280 chip works with maximum voltage of 3.6V (supply voltage range is from 1.71 to 3.6V) which means we’ve to use a 3V3 voltage regulator to supply it from a 5V source.
Also, if we’re working with a 5V system (development board, microcontroller …) like the PIC18F46K22 microcontroller, we’ve to use a voltage level shifter (level converter) which converts the 3.3V (comes from the BME280 chip) into 5V (goes to the PIC18F46K22) and vice versa. This level shifter is for the I2C bus lines (clock and data).
The BME280 module shown in project circuit diagram has a built-in 3.3V regulator and level shifter.

PIC18F46K22 BME280 sensor SSD1306 OLED circuit

All the grounded terminals are connected together.

The PIC18F46K22 microcontroller has 2 hardware I2C modules (MSSP1 and MSSP2 modules).
In this project I2C1 module is used with SDA1 on pin RC4 (#23) and SCL1 on pin RC3 (#18). The SDA1 pin of the MCU is connected to the SDA pin of the display and the SCL1 pin of the MCU is connected to the SCL pin of the display.
The reset pin of the display is connected to pin RD4 (#27) of the microcontroller.

The SSD1306 OLED display DC pin is connected to VDD which means I2C slave address of the device is 0x7A.

Generally, the BME280 module has at least 4 pins because it can work in SPI mode or I2C mode. For the I2C mode we need 4 pins: VCC, GND, SCL and SDA, where:
GND (ground) is connected to circuit ground (0V)
VCC is the supply pin, it is connected to +5V
SCL is I2C bus serial clock line, connected to PIC18F46K22 SCL1 (RC3) pin
SDA is I2C bus serial data line, connected to PIC18F46K22 SDA1 (RC4) pin.

The SSD1306 OLED and the BME280 sensor are connected to the same I2C bus (slave devices), SCL and SDA pins of the two devices are connected to SCL1 and SDA1 pins of the PIC18F46K22.
The I2C slave address of the SSD1306 OLED differs from the one of the BME280 sensor, this difference allows the master device (PIC18F46K22) to talk to one of them (only one at a time).

In this project the PIC18F46K22 microcontroller runs with its internal oscillator @ 16 MHz, MCLR pin is configured as an input pin.

PIC18F46K22 with SSD1306 OLED and BME280 sensor C code:
The following C code is for mikroC PRO for PIC compiler, it was tested with version 7.2.0.

To be able to compile the C code below with no error, a driver for the SSD1306 OLED display is required, its full name (with extension) is SSD1306OLED.c, download link is the one below:
SSD1306 OLED mikroC library

for more information about this driver, visit the following post:
SSD1306 OLED display library for mikroC compiler | mikroC Projects

Also, another library for the BME280 sensor is required, its full name (with extension) is BME280.c, download link is below:
BME280 Library for mikroC compiler

after the download of the 2 library files, add both of them to mikroC project folder.

The BME280 I2C address and the reset pin of the SSD1306 OLED display are defined in the C code as shown below:

The driver files of the SSD1306 OLED display and the BME280 sensor are included in the code using the following 2 lines:

Reading the values of temperature, humidity and pressure is done as shown below.
Note that the BME280 library returns the temperature in hundredths °C which means we’ve to divide it by 100, it returns the humidity in relative humidity percent (RH%) in 1024 steps which means we’ve to divide it by 1024 and it returns the pressure in Pa, to get the pressure in hPa we’ve to divide it by 100.

Temperature, humidity and pressure values are displayed on the SSD1306 OLED screen.
If there is a problem with the BME280 sensor (for example wrong device address) the screen will display Connection Error.

1 bar = 10000 Pa = 100 hPa. ( 1 hPa = 100 Pa)
Pa: Pascal
hPa: hectoPascal

Rest of code is described through comments.

Full mikroC code:

The following picture shows a protoboard circuit of the project:

Weather station circuit using PIC18F46K22, BME280 and SSD1306

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