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)