Help with Rf Tx Rx circuits for PIC

[NULS_DT]

I have a potential project that will require an Rf Transmitter and receiver to be interfaced with a PIC.

1.Can anyone suggest a suitable RF module that woyuld be available in the UK that could be used with the PIC.

2. When communicating with the Rf modules, do you use the SERin and SERout commands.

3. Are there any application datasheets on the tpoic?



 

 

[hippy]

<i>1. Can anyone suggest a suitable RF module that woyld be available in the UK that could be used with the PIC. </i>

Maplins sell a cheap RX/TX pair at around 10 GBP. There are a whole range of RX/TX modules from simple bit-banged modules to those which take a serial data stream and pass it over the air handling all the protocol and error correction issues. The more capable the module, the more expensive they are. Google is a good place to start.

In the near future ZigBee devices will be appearing which are something else to consider. Devices like XBee make it very easy to setu p wireless networks, one-to-one and peer-to-peer. No idea of pricing though.

<i>2. When communicating with the Rf modules, do you use the SERin and SERout commands. </i>

Usually.

<i>3. Are there any application datasheets on the topic? </i>

A search of the forum and Google should give plenty of information. My own page on PICAXE wireless comms can be found at ...

http://www.hippy.freeserve.co.uk/picaxewf.htm

 

[manuka]

The 433MHz Tx/Rx modules are simplicity themselves to use with Picaxes,although data massaging makes them more reliable, &amp; DIRT CHEAP (as little as GBP2 !). I've run several &quot;Silicon Chip&quot; articles recently,ref. =&gt; www.picaxe.orcon.net.nz/433txrx.htm <A href='http://www.picaxe.orcon.net.nz/433txrx.htm ' Target=_Blank>External Web Link</a>

ZigBee modules at 2.4GHz will be FAR smarter but more costly, so start with 433 units to get a feel for things.

 

[Jeremy Leach]

Hi , my weather monitor uses the maplins tx/rx pair ... <A href='http://home.btconnect.com/PicAxe_Projects/WeatherMonitor.htm' Target=_Blank>External Web Link</a> if this is any help by way of an example.

 

[hippy]

Stan : &quot;DIRT CHEAP (as little as GBP2 !)&quot;

Unfortunately I've found nothing this cheap in the UK :-(

 

[manuka]

I've been using several types here in NZ, especially quality Jaycar versions ~NZ$10 ( ~4GBP),but generic offerings from Mailtronics <A href='http://www.mailtronics.co.nz' Target=_Blank>External Web Link</a> are under NZ$5 (~GBP2). See these at =&gt;www.picaxe.orcon.net.nz/433rpt.jpg <A href='http://www.picaxe.orcon.net.nz/433rpt.jpg' Target=_Blank>External Web Link</a>- their Tx even features a compacted spiral antenna that looks like $1M on projects.
Mailtronics only sells within NZ, but I may be tempted to order a swag &amp; send to UK...
Stan

 

[andrewpro]

I've done this before using universal remotes and a bit of hooplah circuitry, but never with a picaxe, so I wont guarantee it'll work...but..

If you use an 08M and some simple transmit circuitry, you can do AM On-Off-Keying through the RF circuitry. The basis is the same as the IR, but using different length pulses of RF instead. You dont need to worry about decoding or anyhting because the picaxe will have it already built in. The code may be a bit thick, so using two 08M's as transcievers would probably be a good idea, depending on what you want to do.

You can make the external circuitry out of stuff from a junk box or really cheap if you buy it (all parts, probably a few dollars US), but it's not an end all solution though. The reason I never bothered to try it with picaxes is that it never really worked that great with the regular remote controls. Interference, frequency drift, reflection images, and all sorts of mysterious things happen, but what the heck. It was fun!!

--Andy P

 

[NULS_DT]

Thanks for that everyone, I certainly have a lot to think about, I have fouund the units in Maplins, and they will be my starting point. I may add a bit of handshake code to protect from interference. Lots to do when school starts again. Thanks

 

[Guest]

You don&#8217;t have to wait for Zigbee modules to arrive before going wireless. I have been using RF600T encoder/decoder chips (also from Maplin) that take data directly from the picaxe serial ports and format it into Manchester encoded packets with CRC and buffering. No special wireless software needed and very simple to connect. Only complication is that the picaxe must run at 8MHz in order to match the RF600T baud rate of 9.6K. Because of all the overheads associated with producing each packet, the over air data rate is only about 800bps but this is all that many low cost wireless links are able to handle anyway.

I still think the best approach would be a new &#8216;Manchester&#8217; serial command for the picaxe to cover all those low cost/speed applications. A real one-chip solution!