RF(433MHz, 418MHz, 315MHz) Module Transmitter/Receiver Pair interfacing with Arduino and 8051(89c512,89c52) Micrcontroller

In this post i am going to explain how to interface cheap RF(Radio Frequency) module pair 433 MHz, 418 MHz or 315 MHz with Arduino uno and 8051(89c51,89c52) microcontroller. Post includes the project source code for both arduino and 89c51 microcontroller, circuit diagram of the project is also available in the tutorial. These cheap RF module pair costs less than $3. They can operate between 3 to 12 volts. Maximum range of the cheap RF transmitter is 200 m at 12 v decreasing the voltage will decrease the range of the transmitter.

RF transmitter and receiver circuits

RF transmitter and receiver module – working

RF module transmit and receive data serially(one bit followed by another). Transmitter receives the dat from external microcontroller and then transmit it over the air. Receiver receives the data, decode it and pass it to the control system attached with it. Both the transmitter and receiver must be working on same frequency for successful data communication. Only the frequency must not be same. Data transmission rate or baud rate must also match with each other. For example if transmitter is working on 9600 bps then receiver baud rate must also be set to 9600 bps.

Any microcontroller have a serial UART(Universal Asynchronous Receiver-Transmitter) port can be used with RF receiver and transmitter. Both 8051 microcontroller and arduino uno have Uart ports. We can connect RF transmitter to one and RF receiver to another in order to transfer data between both of them.

Note: I assume that you are already familiar with the UART(Universal Asynsronous Receiver-Transmitter). If not then first take some tutorials to know about what is UART? and for what purpose it is used?

RF(433MHz, 418MHz, 315MHz) Transmitter Circuit Diagram

I connected the rf(433 MHz, 418 MHz or 315 MHz) transmitter with 89c51 UART port and rf(433 MHz, 418 MHz or 315 MHz) receiver with arduino uart port. Baud rate for serial communication for both 89c51 and arduino is set to 300 bps(bits per second). You can set maximum baud rate up to 2400 bps. But be sure that baud rate for both receiver and transmitter is exactly same.

300 bps is a very low data transmission rate. Tiny RF modules like the one i am using in the tutorial best works on low baud rates. At high baud rates their is a greater chance of data loss during propagating through air. So i also recommend you to use low baud rate when working with tiny short range 433 MHz RF receiver and transmitter.

RF(433MHz, 418MHz, 315MHz) Transmitter Circuit Diagram

Connect the TX(Transmission) pin of UART with ATAD pin of RF transmitter. Supply 3 to 12 v to RF transmitter vcc pin. Ground GND pin of RF transmitter. Microcontroller 89c51 is working on 11.0592 MHz crystal. The led connected to Port-3 pin#6 is for checking if the data is transmitting or not. Led will blink when data starts transmitting from the serial port(TX Pin). Rest of the connections are normal connections which we have to do for running the 8051 microcontroller. Supplying vcc and ground, reset button and internal code execution. I hope you are familiar with the normal connections that we have to do for 89c51 microcontroller.

RF transmission data

I am transmitting continuously “UUU” Character at baud rate 300 bps. If you don’t know about generating baud rate with 89c51 microcontroller. Just go through this small tutorial.

Generating Baud Rate with 8051(89c51,89c52) Microcontroller

RF(433MHz, 418MHz, 315MHz) Receiver Circuit Diagram

Connect arduino with PC/Laptop. Connect the RF Receiver Dout pin with Rx(Receive) pin of arduino uno. That’s all from the receiver side. Locate the Dout pin on RF receiver module, usually its the second pin starting from left. But on different RF modules its at different position. Circuit diagram of our RF receiver interfaced with arduino uno is given below.

All the RF modules works same. But their pin out from different vendors may differ. Some even have eight pins. Data receive pin is only one on all RF receiver’s irrespective of any manufacturer. Similarly transmit pin is only one on ever RF transmitter irrespective of the manufacturer. The extra pins on RF modules are multiple ground pins. CS chip select pins or interrupts(hardly any) etc.

RF(433MHz, 418MHz, 315MHz) Receiver Circuit Diagram

If the character is received by receiver in our case ‘U‘. Since we are transmitting it from the transmitter side. The character will be translated and displayed on the arduino serial monitor. RF received character with it decimal, hexadecimal and binary value is displayed on the arduino serial monitor screen. Since we are continuously transmitting the character form RF transmitter side. So at receiver we must continuously receive the character.

I am displaying received valued in its original format as well as its decimal, hexadecimal and binary value.

Note: Serial.read() function reads the value in decimal form. So if ‘U‘ is received, Serial.read() will read its decimal value. we have to convert the decimal value in to its equivalent ASCII character to display it on arduino serial monitor. The statement char b=(a-‘0’)+0x30; is converting the decimal value in to its equivalent ASCII character. Which is then displayed on serial monitor of arduino uno.

Download the project code, folder contains the arduino sketch written in arduino ide and keil u-vision-4 project files. Hex file of the code is also in the folder. Please give us feedback on the project. If you have any questions Write them below in the comments section.