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#Elster EnergyAxis LAN (EA_LAN)

##General Observations

EA_LAN is a mesh network that operates in the 915MHz ISM (902-928MHz) band. [1]
The channel width is 400kHz, with the first channel at 902.8MHz. [2]
Devices on the EA_LAN utilize a pseudo-random frequency hop table, with each packet taking place on the next frequency in the table. [2]
The Elster Rex2 (R2S) electric meter is powered by the Texas Instruments CC1101 / CC1110 [3]
Packets are transmitted in one of two modes:
- Mode 1
  - 35.5555kBaud
  - Manchester encoding
- Mode 2
  - 142.222kBaud
  - NRZ encoding
Each packet starts with a 19.8ms (704 symbols) preamble consisting of alternating low/high at 35.5555kBaud (Manchester encoded 0's)
Next, 1.8ms (64 symbols) of high/low. (Manchester encoded 1's).
Following this preamble, one of two sync words are seen:
- Mode 1 - 0x55A59AA6
- Mode 2 - 0x9A99A656
In the case of mode 2, the transmission switches to 142.222kBaud NRZ encoding.
Each packet starts with a length prefix (Mode 1: 1 byte, Mode 2: 2 bytes)
Each packet ends with a 2 byte checksum suffix (CCITT CRC16 w/ 0x8408 polynomial)
- Note: Length does not include prefix or suffix

TODO: add screenshots

##Example Messages ###Mode 1

280800a14625000000001c00220b2e4a0000000000000000400007000b082100208066e893b707018dfb

###Mode 2

00360100a146258066e8931c051000005600000000001f086a7e000a00179e179d0600269600273784eb00360038009e00a001dd01e3faa3

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