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The NEXA/PROOVE Remote Protocol
===============================

The RF remote control transmitters/receivers from NEXA and PROOVE seems 
to originate from ARC Technology Co Ltd, Taiwan. There are several versions 
of these products but they seem to share the same protocol.


Bit representation
------------------
The bit coding used by the encoder chips, for example M3E. from 
MOSDESIGN SEMICONDUCTOR,  allows 
for trinary codes, ie '0','1' and 'X' (OPEN/FLOATING).
However, it seems that only '0' and 'X' is currently used in the 
NEXA/PROOVE remotes. 
The high level in the ASCII-graphs below denotes the transmission 
of the 433 MHz carrier. The low level means no carrier.

'0' bit:
 ____              ____
|    |            |    |   
|    |            |    |
|    |____________|    |____________

|<-->|<---------->|<-->|<---------->|
   T       3T        T       3T

'1' bit:
 ____________      ____________
|            |    |            |   
|            |    |            |
|            |____|            |____

|<---------->|<-->|<---------->|<-->|
      3T        T       3T        T

'X' (OPEN) bit:
 ____              ____________
|    |            |            |   
|    |            |            |
|    |____________|            |____

|<-->|<---------->|<---------->|<-->|
   T       3T            3T       T

'STOP/SYNC' bit (Note! Longer than the data bit):
 ____             
|    |    
|    |            
|    |__________________________...____

|<-->|--------------------------...--->|
   T                32T


              
If the time T is 350us, one data bit time is 8 T; 2.8ms.


Packet format
-------------
Each packet is made up of 12 trinary bits followed by a stop/sync bit.
Packets are sent n*4 times or more.

If we call the 12 data bits b0..b11 where b0 is sent first, they will have the 
following meaning:

b0..b3 (4 bits) - House (address)
0000 - A
X000 - B
0X00 - C
XX00 - D
00X0 - E
X0X0 - F
0XX0 - G
XXX0 - H
000X - I
X00X - J
0X0X - K
XX0X - L
00XX - M
X0XX - N
0XXX - O
XXXX - P


b4..b7 - Unit
0000 - 1
X000 - 2
0X00 - 3
XX00 - 4
00X0 - 5
X0X0 - 6
0XX0 - 7
XXX0 - 8
000X - 9
X00X - 10
0X0X - 11
XX0X - 12
00XX - 13
X0XX - 14
0XXX - 15
XXXX - 16


b8..b10 - Unknown
0XX

b11 - Activation
0 - OFF
X - ON


Note! This work is partially inspired by the previous work 
done by Per Mellander.
http://www.mellander.org/per/projects/?project=nexa


Revision History
----------------
2006-10-05   Tord Andersson   Created
2006-10-13   Tord Andersson   Added chip manufacturer (MOSDESIGN)