AVR Microcontroller. RF433 Wireless Temperature Sensor With LCD. Wireless Communication Between Temperature Sensor and Display

Hi, world! In this instruction, I'm explaining how to make a simple wireless temperature sensor that is based on the AVR ATMega328P. The monitoring device is equipped DS18B20 digital thermometer. The sensor sends temperature data to the display using 433Mhz wireless communication. Measurements are displayed on LCD NOKIA 5110. Basically, I using one ATMega328P to control the Transmitter and one ATMega328P to control the Receiver. The transmitter and receiver are connected to the microcontroller via UART. I have also included a circuit diagram of this example for those of you who find it easier to understand the structure of the device through visual representations. I am going to assemble the device prototype and create a C program for the microcontroller using Atmel Studio integrated development platform.

The device includes the following base electronic elements:

Microcontroller Atmel AVR ATMEGA328P

The device uses the following peripheral feature of the microcontroller (see block diagram):

The transmitter and receiver are connected to the microcontroller via The Universal Asynchronous Receiver and Transmitter. UART capability of the Atmega328P allows you to easily communicate the microcontroller with other devices that support UART. It is the primary interface to many other devices, such as GPS receivers, other microcontrollers.

Serial Peripheral Interface for display interfaces to the microcontroller:

SPI is a useful data transfer protocol for microcontrollers. Unlike UART, SPI is synchronous, meaning data transfers are synchronized to a shared clock signal between the two communicating devices. This significantly simplifies the implementation at a hardware level, requiring little more than shift registers, and also means that the baud rate between devices does not have to be agreed on beforehand.

16-bit Timer Counter interrupt for counting of time

Pair of 433 Megahertz modules

The transmitter FS1000A

• Working voltage: 3-12V. Higher voltage it's more power it's more range
• Current while transmitting: 28milliAmpers
• Range: up to 200meters
• Data speed: up to 10 Kilobytes per second, but range drops considerably with speed above 2400 bit per second

The receiver XY-MK-5V

• Voltage: 5Volt. Very sensitive to voltage fluctuations. Always use stabilized power source and decoupling capacitor
• Current while standby: 4 milliamperes

Monochrome Graphic Display NOKIA 5110 with Internal Controller Driver PCD 8544

The PCD 8544 is a low-power CMOS LCD controller/driver, designed to drive a graphic display of 48 rows and 84 columns. All necessary functions for the display are provided in a single chip, including on-chip generation of LCD supply and bias voltages, resulting in a minimum of external components and low power consumption. The PCD 8544 interfaces to microcontrollers through a serial bus interface.

Programmable Resolution 1-Wire Digital Thermometer

The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements. The DS18B20 communicates over a 1-Wire bus, that by definition requires only one data line (and ground) for communication with a microcontroller. Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems inside buildings, equipment, or machinery, and process monitoring and control systems.

To create a wireless temperature sensor I have developed a circuit diagram that looks like it on the picture

I wrote C code programs for transmitter and receiver microcontrollers. My explanation of the code will not be detailed, and if you have any questions, please leave them in the comments.

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Download the С-code programs of the firmware microcontroller. Then compiling them to executable HEX files.

The hex files of the wireless temperature sensor and receiver are ready to be loaded into the chips. I burn the program into the memory of the ATMega 328P microcontroller using AVRDUDE software and an ISP programmer. Watch the video with a detailed description of the microcontroller flash memory burning.

Ok! Now, the device works in accordance with the instructions of the program. Let's check it out.

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