PIC18F46K22 with SSD1306 OLED and LM35 sensor | mikroC Projects

This tutorial shows how to interface PIC18F46K22 microcontroller with SSD1306 OLED display and LM35 analog temperature sensor.
In this project the SSD1306 OLED display (128×64 pixel) is used to display environment temperature in degree Celsius, Kelvin and degree Fahrenheit.
MikroC PRO for PIC compiler is used in this project.

The LM35 temperature sensor is a three pin device (VCC, OUT and GND) with an output voltage linearly related to Centigrade temperature. Since the LM35 output varies with dependent to the temperature, we need an ADC (Analog-to-Digital Converter) module to measure this voltage. The PIC18F46K22 microcontroller has one ADC module with 10-bit resolution.

The LM35 output has linear +10mV/°C scale factor means the following:
If the output voltage =   10mV —> temperature =   1°C
If the output voltage = 100mV —> temperature = 10°C
If the output voltage = 200mV —> temperature = 20°C
If the output voltage = 370mV —> temperature = 37°C
and so on.

To see how to interface PIC18F46K22 microcontroller with LM35 sensor, visit the following post:
Interfacing PIC18F46K22 with 7-segment display and LM35 sensor

And to see how to interface PIC18F46K22 MCU with SSD1306 OLED display, take a look at the following project:
Interfacing PIC18F46K22 with SSD1306 OLED display | mikroC Projects

Hardware Required:

  • PIC18F46K22 microcontroller   —->  datasheet
  • SSD1306 OLED display
  • LM35 temperature sensor   —->   datasheet
  • 5V source
  • Breadboard
  • Jumper wires

PIC18F46K22 with SSD1306 OLED and LM35 circuit:
The image below shows project circuit diagram.

SSD1306 OLED LM35 PIC18F46K22 microcontroller circuit

All the grounded terminals are connected together.

The LM35 sensor has 3 pins (from left to right):
Pin 1 is power supply pin, connected to circuit +5V
Pin 2: output pin
Pin 3: GND (ground), connected to circuit ground.

The output pin of the LM35 sensor is connected to pin RA0 which is analog channel 0 (AN0).

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.

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

PIC18F46K22 with LM335 and SSD1306 OLED 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

after the download, add the driver file to mikroC project folder.

The ADC module is configured so that it uses its internal clock, voltage references (negative and positive) are set to VSS and FVR respectively where the FVR is set to 1.024V:

PIC18F46K22 ADC module is used with 10-bit resolution which means the digital value of the input analog voltage varies between 0 (0V) and 1023 (1.024V).
The digital value represents the temperature in tenths °Celsius (output value of “274” equals 27.4 °Celsius).
The temperature in tenths degree Fahrenheit =  (tenth °Celsius) x 9/5 +320 (because: °F = °Cx9/5 + 32) and the temperature in tenths Kelvin = (tenth °Celsius) + 2732 (because: K = °C + 273.16).

To get the actual value of each quantity we’ve to divide it by 10. The line below shows an example for temperature in Kelvin:

We get the first 3 digits by dividing the tenths value by 10, and the tenths number (number after the decimal point) of the actual temperature value is equal to the reminder of that division (tenths value % 10).

The resolution of this thermometer is 0.1°C.

Full mikroC code:

LM35 SSD1396 OLED PIC18F46K22 circuit


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