Problems on RF communication between PIC

[Mani Yuvan]

i want to sent some letter serially to another micro controller and display it on lcd .I set the the baud rate 9600 bps.when i m testing on board(without using RF module ) it will work fine. but when i Inserting RF module it is not working and nothing to display on lcd.
I use pic18f452 controller and crystal is 20Mhz.

Any one please help me

 

[wizpic]

Rf is pretty tuff to get correct with timings, try sending some preamble first has it sounds like to me the RX unit it missing the data, like a few $55 in front first to help improve timing
it would also help to know what language your writing the code in, you can also try 2400 baud rate

 

[Mani Yuvan]

Rf is pretty tuff to get correct with timings, try sending some preamble first has it sounds like to me the RX unit it missing the data, like a few $55 in front first to help improve timing
it would also help to know what language your writing the code in, you can also try 2400 baud rate

I m using C18 code. and 434 MHz RF module

 

[FvM]

As a general problem, most cheap RF modules, particularly of ASK type, have problems to transmit plain UART code. Besides sending a preamble as mentioned by wizpic, you would ideally implement manchester encoding and bit synchronization on the receiver side. This means, that the received data can't be send to a hardware UART but must be decoded in software.

mikroC has a Manchester Code library that performs this task, there's also a respective Arduino library.

 

[Mani Yuvan]

i m using MPLAB c18 code. and im newer to MCu. may you brief the manchester encoding. and i used tx and rx of RF module directly connect the TX RX pin of microcontrollers

 

[FvM]

Did you search Edaboard for manchester encoding? A lot of threads related to the problem are listed. For the general principle see https://en.wikipedia.org/wiki/Manchester_encoding

 

[Mani Yuvan]

when i change the baud rate to 2400 bps nothing to display even i directly connect the tx rx pin

 

[wizpic]

when i change the baud rate to 2400 bps nothing to display even i directly connect the tx rx pin

you have to change both TX&RX code,

 

[Mani Yuvan]

you have to change both TX&RX code,

i change both tx and rx . but i work on proteus simulation but in hardware working board nothing to display

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is there any way connect RF module to Microcontroller without using encoder and decoder.Im only familiar with c18 compiler.

 

[MUKESH.K.S]

Please try the attached circuit for receiver of rf module .... this circuit has worked fine for me.
Include the code to detect and clear OERR error and FERR error in the receiver micro-controller , the rf module can make such errors.
Try the lowest baud rate .
If u use zigbee module instead of 433Mhz rf module , you will get reliable operation..

 

[Simao.Berkof]

Yeap, try 1200 or lower baudrate

 

[Mani Yuvan]

Yeap, try 1200 or lower baudrate

i have one doubt.I directly connect the data pin to the tx of pic and another receiver data pin to the rx of another pic and i use the Piece of wire for the antenna. And how to i know whether the RF module working or not

 

[MUKESH.K.S]

To check the Rf module follow this procedure
1. Connect vcc and gnd to tx and rx , also connect a piece of wire as antenna on both
2. Apply 5v on data pin of tx ,then check the data pin of rx , if module is good it will also show 5v
3. Apply gnd on data pin of tx ,then check the data pin of rx , if module is good it will also show 0v. Some modules shows 3v instead of gnd, that's why its not working. The ckt i have given above can solve this problem.....trust me i have used this method successfully many times before

 

[Mani Yuvan]

To check the Rf module follow this procedure
1. Connect vcc and gnd to tx and rx , also connect a piece of wire as antenna on both
2. Apply 5v on data pin of tx ,then check the data pin of rx , if module is good it will also show 5v
3. Apply gnd on data pin of tx ,then check the data pin of rx , if module is good it will also show 0v. Some modules shows 3v instead of gnd, that's why its not working. The ckt i have given above can solve this problem.....trust me i have used this method successfully many times before

It works mukesh.when i apply power.check data in pin 4.94 v and check receiver side check the data out pin 4.74 v.when i place data pin to gnd and check rx side it shows 1.24 v.if i used that circuit mean the problem will solved ah??

 

[MUKESH.K.S]

Yes that circuit i have used many times . It works well... just try it . That circuit is very simple ,that consists two inverters ,
the first inverter will turn on only when the voltage exceeds 3.3v.