DHT11 Interface with PIC12F1822 microcontroller – CCS C

In this blog there are some topics talking about the DHT11 relative humidity and temperature sensor and how to interface it with different types of PIC microcontrollers. The datasheet of the DHT11 sensor shows its characteristics and how it works.
Also the following topic shows the DHT11 timing and how to simulate it using Proteus:
Interfacing PIC16F877A with DHT11 (RHT01) sensor Proteus simulation

This topic shows how to interface this sensor with the microcontroller PIC12F1822. This microcontroller has only 8 pins and 6 of them can work as an I/O pins.
An LCD is used to display temperature and relative humidity values. A shift register is used to make a 3-wire LCD as shown at the following link;
Interfacing PIC12F1822 microcontroller with LCD display – CCS C

Therefor for this simple project we need 3 data lines for the LCD and 1 line for the DHT11 sensor which means we need 4 I/O pins.

Components List:

  • PIC12F1822 Microcontroller
  • DHT11 (RHT01) Sensor
  • 1602 LCD
  • 74HC595 Shift Register (74HC164 or CD4094 can do the job)
  • 10K Variable Resistor
  • 4.7K Resistor
  • +5V Power Supply
  • Breadboard
  • Jumper Wires

Interfacing PIC12F1822 with DHT11 sensor circuit:
PIC12F1822 DHT11 humidity and temperature sensor circuit

The shift register data line is connected to RA0 pin and the clock line is connected to RA1 pin. LCDs enable pin is connected to pin RA3.
The internal oscillator of the PIC12F1822 microcontroller is used.
To see how to use 74HC164 or CD4094 instead of 74HC595 go to the link above.
The DHT11 sensor has 4 pins:
VCC : Positive power supply (+5V)
DATA : Sensor data input and output
NC : Not connected terminal
GND : Ground (0V)
A pull-up resistor must be added between the DHT11 data pin and VCC (+5V) pin as shown in the circuit schematic (4.7K ~ 10K).

Interfacing PIC12F1822 with DHT11 sensor CCS C code:
If you want to understand the code please read the DHT11 datasheet.
Variables Time_out and k are used to test reading time to avoid wrong data reception and microcontroller hanging.
The microcontroller runs with its internal oscillator at 32MHz (8MHz + PLL).

Interfacing PIC12F1822 with DHT11 sensor video:

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