Landis+Gyr GridStream Protocol

Reverse Engineering and Analysis

Packet Structure

Sync and Header

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The sync word that the Landis+Gyr smart meters send is shown below, this can be used in GNU Radio or other tools to receive only packets transmitted by the meters. Note that at the start of the header we begin using start and stop bits. These must be stripped off of the rest of the data packet during processing.

Sync and Header

Sync						Header
0xAA	0xAA	0xAA	0xAA	0xAA	0xA	0x00	0xFF	0x2A
10101010	10101010	10101010	10101010	10101010	1010	0 00000000 1	0 11111111 1	0 00101010 1

Using GNU Radio it was found that shortening the Sync requirements a bit and incorporating part of the header leads to the cleanest data for further downstream processing. The modified sync shown in 8 bit chunks is shown below.

Sync Word used with GNURadio

0xAA	0xAA	0xAA	0xAA	0xA0	0x05	0xFF
10101010	10101010	10101010	10101010	10100000	00000101	11111111

The final byte of the sync (0x2A) along with it's start and stop bits are discarded as part of the processing.

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Type, Length and Sub Type

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So far only two types of packets have been observed, a 0x55 and a 0xD5 packet. Multiple lengths and SubTypes of these are listed below.

	Type	SubType	Length	Packets Purpose
1	0x55	0x30	0x0023	Report up-time and other unknown data
2	0x55	0x30	0x0028
3	0xD5	0x21	0x0016
4	0xD5	0x21	0x0017
5	0xD5	0x29	0x0016
6	0xD5	0x29	0x0017
7	0xD5	0x51	0x0047
8	0xD5	0xC0	0x00FD

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Data

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Add data here

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Checksum

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uint16_t Landis_crc16 (uint16_t crc, const std::vector<uint8_t> &data, size_t size) {

// CoServ CRC = 0x45F8

// Oncor CRC = 0x5FD6

// Hard coded Poly 0x1021

    uint16_t i = 0;

    while (size--) {       

crc ^= data[i] << 8;

i++;

for (unsigned k = 0; k < 8; k++)

crc = crc & 0x8000 ? (crc << 1) ^ 0x1021 : crc << 1;     

    }     

return crc;

}

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Captured Meter Data

There have been two packet types observed thus far, a 0x55 and a 0xD5 packet.

• 0x55 appears to be broadcasts from the meters and happen frequently. They have been observed multiple times per minute from a single meter.

• 0xD5 appears to be a packet for transporting data across the mesh network. Each D5 packet will contain two meter ID's, Meter ID #1 and Meter ID #2. There are many 0xD5 packet length and types that have been observed, some are shown below.

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0x55 Meter Data

The data below was captured from the same meter (F0EE36DB) and shows some of the values that can change with each transmission. Different meters have different fixed data and some of the data changes less frequently as well.

0x55 Captured packets from Meter F0EE36DB

Pkt	1	2	3		4	5	6	7	8	9	10	11	12	13	14	15	16		17	18
	Not part of CRC calc				Data
	Header	Type	Length		SubType	Unknown	Unknown	Unknown	Unknown	Counter	Uptime (seconds)	Unknown	Meter ID	Unknown	Unknown	Unknown	Unknown		CRC	Trailing
1	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	0C	0001ECBF	A483	F0EE36DB	0100	2132	04384F	7E80		0896	04
2	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	16	0001ECC6	A483	F0EE36DB	0100	2132	043AC5	7E80		F47E	04
3	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	2A	0001ED05	A483	F0EE36DB	0100	2132	041207	7E80		A412	04
4	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	34	0001ED29	A483	F0EE36DB	0100	2132	041FF9	7E80		D9C4	04
5	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	38	0001ED37	A483	F0EE36DB	0100	2132	042571	7E80		963C	04
6	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	42	0001ED5C	A483	F0EE36DB	0100	2132	0433A9	7E80		8384	04
7	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	4C	0001ED60	A483	F0EE36DB	0100	2132	04354D	7E80		2CB6	04
8	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	4E	0001ED79	A483	F0EE36DB	0100	2132	043F25	7E80		871A	04
9	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	60	0001EDA6	A483	F0EE36DB	0100	2132	040F05	7E80		25C9	04
10	00FF2A	55	0023		30	FFFFFFFFFFFF	50	CF8DD9E2	C0	6A	0001EDCD	A483	F0EE36DB	0100	2132	041E55	7E80		F33F	04

1) Header = 0x00FF2A

2) Packet Type = 0x55

3) Packet Length = 0x0023

4) SubType = 0x30

5) Unknown = FFFFFFFFFFFF (Empty Data Slot?)

6) Unknown = 0x50

7) Unknown = CF8DD9E2 (Appears to either be location identifier or duplicate meter ID in some cases)

8) Unknown = C0

9) Counter = 02 (Increments some amount with each transmission and rolls over at 0xFF)

10) Uptime = 0x0001ECA3 (Value in seconds since meter powered on, easy way to see last time there was an outage!)

11) Unknown Identifier #5 = 0xA483

12) Meter ID = 0xF0EE36DB

13) Unknown = 0x0100

14) Unknown = 0x2132

15) Unknown = 0x042D19

16) Unknown = 0x7E80

17) Checksum = 0xF154

18) Trailing byte = 0x04

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0xD5 Meter Data

There appear to be multiple packet lengths and styles for the 0xD5 packet. There are some samples below showing

0xD5 Captured packet

Pkt	1	2	3		4	5	6	7	8	9	10		11	12
	Not part of CRC calc				Data
	Header	Type	Length		SubType	Meter ID #1	Meter ID #2	Unknown	Unknown	Unknown	Unknown		CRC	Trailing
1	00FF2A	D5	0016		21	F05FCB84	F0FC4DB1	E288	0100	273205	00781930		CB72	00

1) Header = 0x00FF2A

2) Packet Type = 0xD5

3) Packet Length = 0x0016

4) Unknown = 0x21

5) Meter ID #1 = F05FCB84

6) Meter ID #2 = F0FC4DB1

7) Unknown = 0xE288

8) Unknown = 0x0100

9) Unknown= 0x273205

10) Unknown = 0x00781930

11) Checksum = 0xCB72

12) Trailing byte = 0x00

00FF2A D5 0016 21 F073B577 F062363D FA88 0100 1F6C04 14E93E70 CF80 04

00FF2A D5 0017 29 8073AEAC F0F28D56 1288 0100 1F3204 041CBB1930 2D2A 04

00FF2A D5 001B 21 F10679E2 8073CE7D F498 0100 106C02 0A15F9055F06571A80 37C5 00

00FF2A D5 001C 29 8073ADB3 8073CE7D 9088 0100 106C02 040A99CF055F3A4B1170 A696 04

00FF2A D5 0021 22 F05A1A60 8073CE7D D8010100106C020520301D81800A99CF055F3ADD1410 A560 04

00FF2A D5 0047 51 F05A4BCC F03D4CD7 5A6032F37F0001DA2E00022BE9 A483 010150D075D9E2E0 F03D4CD7 000103240403030806080801000000036EE8001F6C0401E9203020818018C22930 9294 00