PIC to control NEXA remoteswitch

[Archangel]

Yes, the Parallax transmitter and reciver works fine, no problem...
I can read data sheets!!!

OK, sorry, I thought that was what you were having trouble with. From fishing the internet this thing looks a lot like X10 controls, and I am guessing you want to control it without interfacing to a nexa transmitter, yes?

[Fredrick]

Yes i want to control it from the Parallax transmitter.

And yes the protocol seems to look like the X10 but there are some diffrents becouse the X10 funtion in PBP does´t work.

[Archangel]

And the assembly code posted above . . where did it come from, and do you have the include file system.inc? the other one I think comes from MPASM.
The web pages I visited list these for sale in Swedish speaking countries only. I think these are over my head, sorry.

[ardhuru]

Seeing the actual original signal would make it much easier, right?

Use the original transmitter, and a compatible RF receiver; feed the output to the soundcard and capture this signal, and study it using any sound editor (Audacity / Goldwave) (more details on this technique at Dave Houston's site).

It would then be much easier to replicate this signal.

Regards,

Anand

[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*