rf 433mhz and avr

[sherazi]

hi firends,

as usual i am here for some basic questions, i want to link a rf remote control to my existing project... and i have tried to Google "RF MHz" and lots of other queries for the purpose... but couldn't get the very basic answers to questions that arose in my mind....

do any one have a basic tutorial or link to it for this purpose?

my needs are a system capable of learning a number of remotes,
the remote just provides a pulse on the relevant pin,
2 channel

what i need help on is....

1 what would be the best approach?[ using decoder chips or uc]
2. how do i link the remotes,[software]
3.is it that i need to use the Rx TX module and connect it to avr's Rx/TX and use the data from udr register, ... or are there any intermediate stages, specially in Manchester coding and decoding....

sorry for asking some weired questions but thats how i am going to understand it...

 

[(*steve*)]

Do you have existing remotes, or are you planning to build your own?

If the former, then you need to get data on them. It may not be trivial to implement anything if these are "secure", i.e. they transmit a different code each time. It also may not be trivial to implement if they simply send a carrier without any modulation (or the same modulated signal)

What you need is for each remote (or each channel) to send a unique and invariant signal that you can decode.

Once you can decode the signals and determine which signal you have, then you can identify the remote and channel.

There are some chips available which can do the decoding for you, but they have to be matched with their opposite number in the remote.

A more general approach is to use a microcontroller to do the decoding and analysis, and then "learning" becomes a possibility. You may have to write some fancy code and you'll need a uC with acess to (internal or external) flash memory (or eeprom etc) to store the "learned" data.

 

[sherazi]

thanks steve...
i have to make a new start so, i would biuld the remote as well, keeping this in mind, now what will you suggest which way should i go, for coders and decoders? or uC ...
what are the Pros and Cons .... and how to go ahead and start for a newbie....

 

[sherazi]

ok, i had some reading
but still have some issues?

do i have to give each transmitter a unique adress? answer seems to be yes, so this has to be done in software?.....
and how would i make the reciever be programed for a specific remote/transmitter... should it be like that when the learn/program button is pressed the reciever recieves the code that is transmitted by the transmitter and saves the code[fixed code] in eeprom? and then after word respond to that remote only?

and for adding another remote simmilar procedure is done but now durring validation the reciever compares code with all stored codes and after that it validates it or make it in valid?


basically i need the algorithm for such remote.... can any one help me regarding that ...? as far as the modules are considered i dont have problems in them.... they are just a link... other than that the whole algorithm of using multiple remotes and their addressing that is required...


sorry for being so confusing.....

 

[(*steve*)]

Do each of the transmitters have a different function? If so, then yes. If the remotes will be interchangeable, then no.

You might look for a chipset used in these transmitter/receiver pairs. I know that some exist which have several "channels" (really button encodings). If each transmitter uses a different "button" then the receiver could be used to decode which remote it is sensing.

Using a PIC is another approach. decoding an incoming signal is not always trivial and you have to include a lot of additional redundant data to ensure that random noise isn't picked up as a valid signal.

 

[sherazi]

each transmitter has two channels,,, and all remotes have same functions

ok.. just have the application in mind..

you would have seen automatic gates that require remote controls... now there are several gates so diffrent gates work with different address so taht they can be differenciated by the recievers... and even some gate have more than 1 remote so that a number of users can have thier own....

 

[(*steve*)]

So do you want a press of any remote to open any/all gates, and pressing the other button will close any/all gates?

 

[sherazi]

No, i have to make a remote , just like a normal rf link...

probably i made confusion by using the word "lock"

so i have a two channel remote system [receiver / transmitter].. by having some study i got the idea .. i have to use a micro controller and a 433MHz module for Rx and Tx
and to make the remote work with its own receiver we use fixed code.. so that the reciever doesnt react to other signals...

thats OK for working with just dedicated pairs[ specific transmitter for spec. receiver] but as you know for gates more than 1 remote are used for the same receiver... for that what we have to do? we have to add the addresses of all remotes to the receiver so that when any RF signal is received the receiver instead of checking just one address matches it with all available addresses that are stored and if any one matches it considers it a valid one

 

[saur]

yes, it looks to be correct to add the addresses of remotes in Rx and it checks the correct one that matches when a remote tries to control.