DR + GPS
STARTER KIT REFERENCE MANUAL
Lassen DR + GPS Reference Manual 47
The table below provides the message structure for a simple data packet of N
M-bytes. Each message has five framing bytes: SOM; two message ID bytes
(PCOD and PSUB); a checksum byte; and EOM. The data type and data
structure in the message (i.e., the parser) is specified by the Parser code PCOD
and parser subcode PSUB.
Table 10: HIPPO Report Message Structure
Byte Meaning Value
SOM start of message 0x81
PCOD Parser code 0x00 – 0x7F
PSUB Parser subcode 0x00 – 0x7F, 0xFF
D[0] First byte of data 0x00 – 0xFF
D[1] Second byte of data 0x00 – 0xFF
… … …
D[N-1] Last byte of data 0x00 – 0xFF
CS Checksum 0x00 – 0xFF
EOM End of message 0x82
Some parser code / subcodes have data indexed by channel or satellite, as
shown in the table below. The index is the first byte after the parser subcode.
The parser code/subcode specifies whether a message uses indexing.
Table 11: HIPPO Report Message Structure (Indexed Data)
Byte Meaning Value
SOM start of message 0x81
PCOD Parser code 0x00 – 0x7F
PSUB Parser subcode 0x00 – 0x7F
INDEX Data indexed by channel, etc. 0x00-0x7F, 0xFF
D[0] First byte of data 0x00 – 0xFF
D[1] Second byte of data 0x00 – 0xFF
… … …
D[N-1] Last byte of data 0x00 – 0xFF
CS Checksum 0x00 – 0xFF
EOM End of message 0x82