RX/TX modules

Most of these ready made RF modules are transparent serial in-out devices. If you feed a digital serial data stream in at one end, it comes out the other end, no need for any other "driver". Usually you'd have a microcontroller at either end and you communicate from micro to micro using the internal USART, so I guess you could call the micro the "driver". The micros don't know the difference between hard wiring together or running through these RF modules, they are just transmitting and receiving serial digital data.

For example, lets say you had 5 digital inputs and you wanted to trasmit these digital signals to a reciever at the other end to control

5 LEDs or whatever. You could use a PICAXE chip at the input end which scans the 5 inputs and sends a unique byte to the transmitter for each input saying if it's HIGH or LOW. Another PICAXE at the receiving end decodes this serial data sets the 5 outputs HIGH or LOW as required.

Hope that helps.

Dave :)

Thanks Dave for the info. I sorta get what you are trying to say. I looked up PICAXE on the net

briefly and can see these chips are programmable I/O chips... looks relatively easy, even for some of my other apps.

Am I on the right track here? (block diagram) : Digital signals > Picaxe > TX Data Pin(Out) ~ ~ ~ Transmission ~ ~ ~ RX Data Pin(In) > Picaxe > Outputs.

What if I only have 1 digital input that I want to transmit to the receiver at the other end? Would I still need a chip like the Picaxe on either end, or not?

Regards, Jason.

Yep, they are an easily programmable microcontroller. Perfect for a job such as this.

Correct, that's all you do.

Most likely you still need the PICAXE or some other microcontroller. Most RF modules are designed for a serial input, so need a minimum input "data rate" like 300baud. You can probably get modules that have digital level inputs though.

Dave :)

Cool! I shall see how I go. It's great to know that these chips also come in different sizes (8/18/28/40pin)!

Thanks again Dave.

Regards, Jason.

Silicon Chip have a regular PICAXE column and lots of good PICAXE projects, worth following.

Once you've mastered PICAXE's you can step up to regular microcontrollers like PIC or Atmel AVR programmed in BASIC, C or even assembler.

Also, as I mentioned in another thread, I think there is even a PICAXE uses group based in Sydney that meets every month.

Have fun!

Dave :)

Much appreciated Dave. I'm gonna have fun with this! I've never used microcontrollers before, and these sound pretty simple enough. I shall have a look at that Silicon Chip column too.

Regards, Jason.

Oh just one for question Dave. I've seen some example schematics of how those TX/RX are connected (typically), and they are connected to Encoder and Decoder IC's. Would I need to sandwich these in between the PICAXE and the Module, or no need? PICAXE>Encoder>TXmodule ~~~Transmission~~~ RXmodule>Decoder>PICAXE ??? I'm sorta guessing that it would depend on how reliable I want the transmission, i.e. noise/interference elimination? Would I be correct to assume this?

Jason.

No need. One of the big reasons to use a little micro like the Picaxe in this kind of device is that you can program it to do all that for you.

No. Most serialparallel chips don't do error checking, & it's much easier to add code for parity (or checksumming, ECC, etc) checking into your program than it is to do it in hardware anyway.

And best of luck with learning the PICAXE, or whatever chip you end up going with. Once you get over the initial learning hump, designing with embedded controllers is a lot of fun, so don't get discouraged if you find it a struggle at first. ;)

--
   W          
 . | ,. w ,   "Some people are alive only because
  \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
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No need if the RF module accepts direct serial input, it already has the "encoder/decoder" inbuilt, or simply doesn't need one. There are RF modules that will not accept a direct digital input and they are more difficult to use. The Jaycar ones will accept digital digital input judging from it having a specification for a certain data rate, but check the data sheet to be sure.

If you want error correction/detection then you'll have to do this in the PIC. More advanced units like wirless RS232 modules will have their own inbuilt error checking. Open one up though and you'll find a microcontroller stuck on the front end of a standard RF module! Basic error detection would use simple parity checking, or you could simply send the same byte say 3 times in row. If the receiver micro does not get 3 bytes the same then it simply discards the data.

Dave :)

Thanks again!

Thanks Lionel!