about the TWS-434A and RWS-434

Hopefully Bruce will read this post, he sells these modules on his site.

I have found schematics that use the TWS and RWS 434 receiver and transmitter, they connect these modules to some decoder I.C.

I was wondering if that decoder is needed at all if I use Picbasic's Serin and Serout.

What's the main difference between the RF modules that use 434Mhz and the ones that use 315MHz? Just the frequency perhaps?

Here's a link to Bruce's site, it one of the schematics I was talking about. http://www.rentron.com/Files/NEW_TWS_RWS_DOC.pdf

thanks in advance.

Art~

I'm very familiar with these modules, having used them in several frequencies. I imported them directly from Wen Shing (after first suggesting to Bruce that he stock other frequencies) although there are now several manufacturers who supply the same design.

To answer your questions - yes, you can eliminate the encoder/decoder - I've posted example code using them to send/receive NEC protocol which I prefer to SerIn/SerOut. And, the only functional difference between the 433.92MHz and 315MHz models is the frequency.

• http://www.picbasic.co.uk/forum/showthread.php?t=6261
  http://www.wenshing.com.tw/english/rask.asp
  http://www.wenshing.com.tw/english/task.asp

If you search, you'll also find many, many threads from people using them with SerIn/SerOut which might say something for my preferred method.

Thanks a lot Dave, that was very useful. I ordered 5 modules for 8 dollars each to begin testing.

The routines Dave posted are a good place to start, and he has a lot more interesting tutorials on his site. Definitely worth a visit.

But, you can definitely send/receive serial data without using encoder/decoder ICs. If you do, you'll want to packetize your data, and probably use a preamble, synch byte, redundant data, and maybe even a checksum.

I use these with serout2/serin2 all the time, and it works exceptionally well, but you do have to learn to deal with noise, and data errors.

You can also develope your own protocol using pulsin at the receiver, and simply taking the transmit pin high/low for specific periods to transmit.

It's pretty easy once you've had time to experiment with different methods. Which one works best normally depends on the application. The more critical the data, the more work it is to send/receive it reliably.

We carried stock of 315MHz, 418MHz and 434MHz TWS/RWS for several years. We had a hard time keeping the 434MHz versions in stock. The 315MHz and 418MHz versions sat there forever. That's the only reason we dropped them.

The NEC protocol sends each byte a second time, in bit-wise complement form, so it has built-in error detection and is very reliable. It's best with sort messages although X-10, Panasonic and others use it or very similar variants with up to 48 bits in each message. Hitachi uses a variant with >100 bit messages.

If you need lots of data, Crestron stuffs a lot into very short messages (10 bit periods with 5 possible states for each) using a combination of pulse width and space width encoding. It can also include forward error correction but it requires some sophisticated math skills (the kind that makes my head hurt) for that.

Bruce's site is full of good stuff, too.