Interfacing PIC16F877A with DS18B20 temperature sensor

Interfacing the popular microcontroller PIC16F877A with the temperature sensor DS18B20 is so easy, in this topic I’m going to show how to build a digital thermometer using PIC16F877A and DS18B20 sensor where the temperature is displayed on 16×2 LCD screen.

Firstable the DS18B20 sensor is a 3-pin electronic component (like a simple transistor) from Maxim (formerly Dallas) which uses 1-wire protocol to communicate with master device (microprocessor, microcontroller ….). Each DS18B20 device has a unique 64-bit serial code, which allows multiple DS18B20s to function on the same 1-Wire bus and controlled with one master device.
The DS18B20 sensor provides 9-bit to 12-bit Celsius temperature measurement resolution (programmable resolution).
The DS18B20 sensor is available in 8-Pin SO (150 mils), 8-Pin μSOP, and 3-Pin TO-92 Packages. DS18B20 pin configurations is shown below:

ds18b20 pin configurations

In this example the master device is the PIC16F877A microcontroller.

Components Required:

  • PIC16F877A microcontroller
  • DS18B20 temperature sensor — datasheet
  • 16×2 LCD screen
  • 8 MHz crystal oscillator
  • 2 x 22pF ceramic capacitors
  • 10K ohm resistor
  • 4.7k ohm resistor
  • Power source with 5 VDC
  • Breadboard
  • Jumper wires

Interfacing PIC16F877A with DS18B20 temperature sensor circuit:
The image below shows the circuit schematic diagram of the project.

PIC16F877A DS18B20 sensor 16x2 LCD circuit

(All grounded terminals are connected together)

The DS18B20 sensor has 3 pins: VCC (+5V), data and GND. The data pin is connected to PIC16F877A pin RB1. The 16×2 LCD module is connected to PORTD pins.

The LCD screen is used to display the temperature value read by the DS18B20 sensor.

Interfacing PIC16F877A with DS18B20 temperature sensor CCS C code:

Functions used in the code:
int1 ds18b20_start(): used to know if the DS18B20 sensor is correctly connected to the circuit, returns TRUE (1) if OK and FALSE (0) if error.
void ds18b20_write_bit(int1 value): writes (sends) 1 bit to the DS18B20 sensor, the bit is ‘value’ which may be 1 or 0.
void ds18b20_write_byte(int8 value): writes 1 byte (8 bits) to the DS18B20 sensor, this function is based on the previous function. This function writes LSB (Least Significant Bit) first.
int1 ds18b20_read_bit(void): reads 1 bit from the DS18B20 sensor, returns the read value (1 or 0).
int8 ds18b20_read_byte(void): reads 1 byte (8 bits) from the DS18B20 sensor, this function is based on the previous function. This function reads LSB first.
int1 ds18b20_read(int16 *raw_temp_value): reads the temperature raw data which is 16-bit long (two 8-bit registers), the data is stored in the variable raw_temp_value, returns TRUE if OK and FALSE if error.

The value of the temperature in degree Celsius is equal to the raw value divided by 16 (in case of 12-bit resolution). The default resolution of the DS18B20 is 12 bits.

Rest of code is described through comments!

Arduino + DS18B20 sensor video:
The video below shows Proteus simulation of this project.

Arduino + DS18B20 sensor + LCD Proteus simulation file download:
Download

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.