PIC to control NEXA remoteswitch

[dhouston]

Here's the URL that Anand referred to...

• http://davehouston.org/learn.htm

Once you capture the codes you merely need to duplicate the timing with your transmitter.

[Bruce]

Try something like this.

DEFINE OSC 4

' Timing as described in NexaProtocol.txt
T CON 350      ' T = 350uS
T3 CON 1050    ' 3T
T32 CON 11200  ' 32T (Stop/Synch)

' Note we're using 1 VS X as shown in text
A1_ON  CON %101100000000 ' 12-bit code for House/Unit A1 ON
A1_OFF CON %001100000000 ' 12-bit code for House/Unit A1 OFF
'           ||||||||||||____ 4-bit House code
'           ||||||||________ 4-bit Unit code
'           ||||____________ 3-bit Unknown code
'           |_______________ 1-bit Activation code 1=ON 0=OFF 

D_PACKET VAR WORD ' Holds 12-bit data packet to send
INDEX VAR BYTE    ' Data packet bit index pointer
LOOPS VAR BYTE    ' Loop counter

TX VAR PORTB.0    ' Connects to RF transmitter data in

LOW TX            ' TX output idles low for RF carrier OFF

Main:
    D_PACKET = A1_ON
    GOSUB Send
    PAUSE 5000
    D_PACKET = A1_OFF
    GOSUB Send
    PAUSE 5000
    GOTO Main
    
Send:
    FOR LOOPS = 1 TO 4    ' send each packet 4 times
      FOR INDEX = 0 TO 11 ' sends 12 bits per pass LSB 1st
        
        HIGH TX           ' The 1st half of a 0 or X  bit period is the
        PAUSEUS T         ' same so no need to repeat this sequence inside
        LOW TX            ' the IF block
        PAUSEUS T3 
        
        IF D_PACKET.0[INDEX]=1 THEN
           HIGH TX        ' send a 1 bit (1=X here)
           PAUSEUS T3
           LOW TX
           PAUSEUS T
        ELSE
           HIGH TX        ' send a 0 bit
           PAUSEUS T
           LOW TX
           PAUSEUS T3
        ENDIF
      NEXT INDEX          ' loop until all 12-bits sent
      
      ' Start of Stop/Synch period after each 12-bit packet
      HIGH TX
      PAUSEUS T
      LOW TX
      PAUSEUS T32
      ' End of Stop/Synch period
      
    NEXT LOOPS        ' send 4 packets per pass
    RETURN
      
    END

Can't say if this works or not since I don't have the receiver to play with, but it looks close
to what's shown in the NexaProtocol.txt timing diagram.

[Fredrick]

Hi Bruce

Thanx for the code, but it does´t work so good but we are close now.

If i have the NEXA switch ON and let the PIC program running for 1 - 5 minutes the PIC turns the NEXA off, but never on again.

Here is more information for the NEXA and source code in some other language..
http://svn.telldus.com/svn/rf_ctrl/t...runk/examples/
http://svn.telldus.com/svn/rf_ctrl/

I have read on a swedish forum that the original NEXA remote control send´s 25 bits but there is only every second bit that contains the data, it sends a "zero" between every bit

http://elektronikforumet.com/forum/v...ht=nexa+proto*

[Bruce]

Hi Fredrick,

I think I goofed on the 3-bit unknown bits. Try changing to this;

A1_ON CON %111000000000 ' 12-bit code for House/Unit A1 ON
A1_OFF CON %011000000000 ' 12-bit code for House/Unit A1 OFF

[dhouston]

If you capture the codes as Anand suggested, I think you will find they are substantially different from what is described in NexaProtocol.txt. The Elro AB600 and Intertechno are among those that use the Arc Technology hardware. Those protocols agree with NexaProtocol.txt as far as A=0000, 1=0000, etc. but the wave shapes differ significantly from the shapes in NexaProtocol.txt. As I recall, the codes I have for Elro AB600 and Intertechno tested OK using a European Pronto (433.92MHz) to send the RF codes.

[Fredrick]

Hi Bruce
I´m inprest of your programing skills, the code now works fine, better than the original NEXA remote control.

I have tryed diffrent housecodes and unit numbers and all works whit no problems.

The PIC can now control the NEXA switch from mutch longer rance then the original remote control.


Many thanx to you Bruce.

[Bruce]

Hi Fredrick,

Excellent. I'm glad you got it working, and happy to help.

We lucked-out having someone else do the dirty work for us...;o}

Dave & Anand both make good points above. If you have access to an O-Scope or can
build the sound card version, it makes the whole process a lot easier. And then you'll be
relatively sure your timing is correct.

I suspect this is what someone did when they wrote NexaProtocol.txt. You can probably
tweak the timing down to near perfect if you scope the data output pin on the NEXA
encoder IC in your transmitter.

At least now you have something to work with, and you can see how the timing from
NexaProtocol.txt was converted to a few simple PBP routines.

Cloning most encoders is relatively simple. The decoding part is a LOT more work.

Maybe you could post what you have now in the code examples section to share with
others?

[Fredrick]

I tryed to do the sound card version today byt no one of my 2 computers have a "Line in" or "Audio in" input, only a input with a microphone symbol on and that does´t work.

I have now posted the code in the code exampel area now.