Author Topic: saw transmitter  (Read 1066 times)

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Offline Mato17Topic starter

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saw transmitter
« on: June 26, 2011, 02:19:18 AM »
Hi, any idea how to accomplish communication between this :http://www.sos.sk/a_info/resource/c/HCS-TX-3.pdf and this:http://www.sos.sk/a_info/resource/c/RTX-MID-3V.pdf ?

I just wonder if that small trasmmiter sends same signal for every button, everytime I press it...
If yes, then I can output those signals to hyperterminal and record them, cant I?

Thanks

Offline waltr

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Re: saw transmitter
« Reply #1 on: June 26, 2011, 07:26:02 AM »
The transmitter is a complete system. The Encoder chip (HCS-300) senses a button press then creates and encoded data stream for the Transmitter to send. A different code is sent for each button.

It is unclear as to whether the RX you linked to is compatible with that transmitter. This looks to be just an OOK receiver and does not have the complementary decoder to the HCS-300 encoder.

Here is the data sheet for the Encoder chip:
http://ww1.microchip.com/downloads/en/devicedoc/21137f.pdf
and here is the complementary decoder:
http://ww1.microchip.com/downloads/en/devicedoc/40183d.pdf

Addition details including sample code can be found on Microchip's web site.


Offline Mato17Topic starter

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Re: saw transmitter
« Reply #2 on: June 26, 2011, 08:40:55 AM »
Yea i know that transmitter encodes data, but ...
If you for instance wanna encode string in pc, and you wanna send string "Hello" encoded string may look "olleH" and you need decoder to get Hello from that.... But if I am wayting only 3 different possibile inputs incoming (like from my transmitter) I dont need to care how to decrypt the inputs, I just assaing 3 different inputs to 3 different buttons, and when i get for example input "xxx" or "yyy" or "zzz" i will know which string represents which button(like "xxx" is 1. , "yyy" is second...), and decryption is not need.

Or RF encoding works in a different way ?

Offline waltr

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Re: saw transmitter
« Reply #3 on: June 26, 2011, 10:17:16 AM »
The transmitter you linked to uses the KEELOQ® Code Hopping encryption. This requires the matching decoder. Read the data sheets I linked to on what these chips do.

There are other button encoder/decoder chips that do not encrypt the data and can send a simple binary sequence that directly matches which button is pressed.

Another issue with the OOK or ASK transmitter/receivers is that you can not just send a arbitrary binary series since the receivers needs to 'lock onto' the incoming data. You need to do more web searches and much more reading. There is plenty of descriptions on using OOK transmitter/receivers on the web and here in the SoR forums (also search the SparkFun forums).


Offline Mato17Topic starter

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Re: saw transmitter
« Reply #4 on: June 26, 2011, 12:37:19 PM »
I understand now, I will read about it. Thanks! :)

 


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