RF communication b/w to microcontrollers

[kapil2910]

Hello Sir,
Please can you help me how to send data and communicate between rf module Transmitter and receiver using Encoder(HT12e), decoder(HT12d) to Two PIC16f877a micro-controller at receiver and transmitters end.
Don't know how to that, What code i have to use, How to wire the connection.
I want to simply connect a 4x4 keypad at Transmitter circuit to micro-controller and LCD at receiver end's Micro-controller and when i press Button on key pad, say 1 then it should be displayed at receivers circuit LCD.
Please held really confused how to do this.
Thanks in advance

 

[jayanth.devarayanadurga]

You don't need HT12E and HT12D to do that. You can use any PIC with UART. Interface keypad to Transmitter board PIC and then Connect RF Transmitter module to UART Tx pin and then in the receiver board connect RF receiver module to UART Rx pin. Connect your LCd to receiver PIC. All you need is Serial transmit code for transmitter PIC and Serial receive Code for receiver PIC.

See this video

If you still want encoder and decoder then you can use software encoder and decoder. If you need to use HT12D and HT12E for some specific purpose then I can write code for it. You have to provide parallel data of 4 bits. 4X4 keypad produces 14 key values 0000 to 1111. These can be encoded using HT12E and then transmitted using RF transmitter. On the receiving end HT12D receives the data and if address is matched then it will send a signal to uC stating that data is valid. If data is valid the decoded data appeard at the 4 o/p lines of HT12D. These can be read into the receiver PIC and then depending upon the 16 values, info like which key was pressed can be displayed on LCD.

 

[FvM]

It's well known that many cheap RF modules, particularly AM types, have difficulties to transmit UART data reliably. If you read the datasheets thorougly, you'll find that they specify a modulation duty cycle of e.g. 30-70% that can be easily achieved with a HT12 encoder, but not by arbitrary UART data.

Some RF module suppliers are also linking Arduino code libraries that are encoding serial data differently to get more reliable transmission. There are various previous discussions at Edaboard, e.g. suggesting a kind of pseudo Manchester encoding transmitted over standard UARTs. I don't want to retell the whole discussion, just mention their existence.