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Overview of Sparkplug-B
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08 9f af b8 f8 8d 31 12 23 0a 14 4E 6F 64 65 20 43 6F 6E 74 72 6F 6C 2F 52 65 62 69 72 74 68 18 9f af b8 f8 8d 31 20 0b 38 00 70 01 18 ff ff ff ff ff ff ff ff ff 01 |
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{“timestamp”: 1687369422751,
”metrics”:[
{“name”:”Node Control/Rebirth”,”timestamp”:1687369422751,
”datatype”:11,”is_null”:0,”boolean_value”:1} // datatype=Boolean
],
”seq”:-1}
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08 c0 b8 d8 9e 8e 31 12 0f 10 9a ef 02 18 c0 b8 d8 9e 8e 31 20 03 50 0f 18 ff ff ff ff ff ff ff ff ff 01 0a |
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{“timestamp”: 1687449640000,
”metrics”:[
{“alias”:47002,”timestamp”:1687449640000,
”datatype”:3,”int_value”:15} // datatype=Int32
],
”seq”:-1}
Interpretation of integer values: Protobuf uses variable-width integers (varint) that allows encoding up to 64-bit unsigned integers using between 1 and 10 bytes, depending on the size of the value. If the most-significant bit (MSB) is a 1, then byte value continues to the next byte. The continuation bit must be dropped in order to calculate the value. Bytes are in little-endian order.
9a ef 02 ==> 10011010 11101111 00000010
drop continuation bits and reverse order: 0000010 1101111 0011010
group bits and calculate: 10110111 10011010 = 0xB79A = 47,002
There are two different ways to encode negative integers in Protobuf (2’s complement or zigzag encoding), depending on the data type used. See Protobuf documentation for further explanation, or below for an example.
DDATA - Device Data Message
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Device Data message (DDATA) reports a set of data values from the RediGate. On initial connection, all values will be reported, and after that typically only changes. The DDATA message may have any number of repeated “metrics” elements with the reported data values. RediGate uses the RTDB register address for the “alias,” and either the RTDB register address or a configured Tag name for the “name” of the data item.
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08 b5 c7 fb a3 8e 31 12 08 10 9d ef 02 20 03 50 05 12 0c 10 9e ef 02 20 03 50 fa ff ff ff 0f 18 2b |
Interpretation of Protobuf payload:
{“timestamp”: 1687460701109,
”metrics”:[
{“alias”:47005,”datatype”:3,”int_value”:5}, // datatype=Int32
{“alias”:47006,”datatype”:3,”int_value”:-6} // datatype=Int32
],
”seq”:43}
Interpretation of the negative integer value in Protobuf encoding:
fa ff ff ff 0f ==> 11111010 11111111 11111111 11111111 00001111
drop continuation bits and reverse order: 0001111 1111111 1111111 1111111 1111010
group bits and calculate: 11111111 11111111 11111111 11111010 = 0xFFFA
take 2’s complement (invert bits and add 1, or subtract from 0x10000): -6
DBIRTH - Device Birth Message
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08 dc dc 84 84 8e 31 12 0e 0a 05 31 30 30 30 31 10 91 4e 20 0b 70 01 12 0f 0a 05 33 30 30 30 31 10 b1 ea 01 20 06 50 13 12 13 0a 05 34 31 30 30 31 10 a9 c0 02 20 03 50 9c ff ff ff 0f 12 12 0a 05 34 32 30 30 31 10 91 c8 02 20 09 65 d0 0f 49 40 12 14 0a 05 34 35 30 30 31 10 c9 df 02 20 0c 7a 05 48 65 6c 6c 6f 18 01 |
Interpretation of Protobuf payload:
{“timestamp”: 1687393742428,
”metrics”:[
{“name”:”10001”,”alias”:10001,”datatype”:11,”boolean_value”:1}, // datatype=Boolean
{“name”:”30001”,”alias”:30001,”datatype”:6,”int_value”:19}, // datatype=UInt16
{“name”:”41001”,”alias”:41001,”datatype”:3,”int_value”:-100}, // datatype=Int32
{“name”:”42001”,”alias”:42001,”datatype”:9,”float_value”:3.14159}, // datatype=Float
{“name”:”45001”,”alias”:45001,”datatype”:12,”string_value”:”Hello”} // datatype=String
],
”seq”:1}
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08 9c c1 84 84 8e 31 12 14 0a 05 62 64 53 65 71 10 63 18 9d c1 84 84 8e 31 20 08 58 00 18 00 |
Interpretation of Protobuf payload:
{“timestamp”: 1687393738908
”metrics”:[
{“name”:”bdseq”,”alias”:99,”timestamp”:1687393738909,
”datatype”:8,”long_value”:0} // datatype=UInt64
],
”seq”:182}
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Example Sparkplug-B message:
08 ae d1 c9 a6 8e 31 18 b6 01 |
Interpretation of Protobuf payload:
{“timestamp”: 1687466174638,”seq”:182}