Category Archives: RF

rf_comm_avr

RF Communication Between Microcontrollers – Part III

Welcome to the 3rd part of RF Communication tutorial. In the last two parts I have introduced the basics of RF Communication. RF Communication Between Microcontrollers – Part I : Introduction to RF Communication and Modules. RF Communication Between Microcontrollers – Part II : Algorithm and general description of data transfer. Part III will be covering mostly the practical part, i.e. we will build a complete & working data transfer system. Here you will get circuit and program to implement the solution. The application is very simple in this case, just to transfer a byte of data from Tx station to the Rx station. Once you implement it and get it working you will have enough information and experience to make other RF based projects. I request all users to follows the instruction exactly as given (unless they are smart enough to know what they are doing). The most important thing in this article is timing of the MCU, so Use the exact frequency crystals as used in the designs. Write High Fuse = C9 (HEX Value) and Low Fuse FF (HEX Value) to enable external crystal. Hardware We will have two units. One is Tx (Transmitter) and Other is Rx (Receiver). Both units are based around ATmega16 MCU(you can use ATmega32 also) on external 16MHz crystal. On the Tx […]

RF Communication Between Microcontrollers – Part II

Hello Friends, Welcome back to the Part II of RF Communication tutorial. Here I will show you the basic working of RF modules and how to send and receive data. Please see the Part I of this tutorial for basic introduction. You should also be familiar with RS232 communication. If you are new to it please see RS232 Serial Communication Tutorial. I also recommend using wireless link only after you have successfully tried wired RS232 communication. Here I will not go deep in how RS232 works because it is already discussed in RS232 Serial Communication Tutorial. I will use my interrupt driven fully buffered USART library for communication. How RF Module Works Working of RF Modules is simple but with a little trick. The working is shown in figure below. Fig- Working of RF Modules.   Here what ever digital data you input on "Data In" of TX is available on "Data Out" of RX. Say, if you set "data in" high, the "data out" will become high as well. But here lies the trick! The fact is that you cannot Keep Logic HIGH or LOW for a Long period of time, say for a few millisecond second. If you apply a logic low on "data in" the "data out" will become low but only for few millisecond and it […]

RF Communication Between Microcontrollers – Part I

In many situations a communication link between to devices becomes essential. This communication can be wired or wireless. If two devices are close to each other (like a MCU and a Memory) a wired link is preferred. How ever in many situations two devices are reasonably far apart. In that case a wireless link is preferred. Two popular wireless communication technologies are IR Communications Used in IrDA, and Remote controls Short Range Requires two devices to be in line of sight. There should be no Opaque Obstacle in between the devices. Easy and low cost to implement RF Communication Widely used, including Bluetooth,Radios,Cell phones, Satellite etc Wide range, from few meters to millions of kilometers (Can be Used to control Robots in Mars) Does not requires two devices to be in line of sight. Can cross many obstacles Circuits can be complicated and costly. In this tutorial we will learn how to practically implement a wireless link between two MCUs. This link will be used to send and receive digital data. We will create a Radio Frequency link. How ever as I said the RF circuits are little complicated so we will use ready made RF Modules. These are easily available and low cost. What is a RF Module ? A RF Module is a small circuit pre built and […]