Field #
Bytes Offset
Data Type
Size
Description
2
1
u8
1
3
2
u8
1
4
3
u16
2
Table 39: ANPP Header Format
11.1.1.1 Header LRC
The header LRC (Longitudinal Redundancy Check) provides error checking on the packet header. It also allows
the decoder to find the start of a packet by scanning for a valid LRC. Only the lower 8 bits of the calculation
below are provided in the LRC field of the packet header. The LRC can be found using the following:
11.1.1.2 Packet ID
The packet ID is used to distinguish the contents of the packet. Packet IDs range from 0 to 255. See
Advanced Navigation Packet Protocol
System packets have packet IDs in the range 0 to 19. These packets are implemented the same by every
device using ANPP.
State packets are packets that contain data that changes with time, i.e. temperature. State packets can be set
to output at a certain rate. State packets are packet IDs in the range 20 to 179.
Configuration packets are used for reading and writing device configuration. Configuration packets are packet
IDs in the range 180 to 255.
11.1.1.3 Packet Length
The packet length denotes the length of the packet data, i.e. from byte index 5 onwards inclusive. Packet length
has a range of 0 – 255.
11.1.1.4 CRC
The CRC is a CRC16-CCITT. The starting value is 0xFFFF. The CRC covers only the packet data.
11.1.2 Packet Requests
Any of the state and configuration packets can be requested at any time using the
11.1.3 Packet Acknowledgement
When configuration packets are sent to Boreas, it will reply with an acknowledgement packet that indicates
whether the configuration change was successful or not. See
External data packets will also generate negative acknowledgement packets if there is a problem with the
packet. Positive acknowledgements will not be sent. See
for a list of External Data Packets.
11.1.4 Packet Rates
The packet rates can be configured either using the web UI, or Boreas Manager or through the
. By default Boreas is configured to output the
at 20 Hz and the
at 20 Hz. When configuring packet rates it is essential to ensure the baud rate is
capable of handling the data throughput. This can be calculated using the rate and packet size. The packet size
v1.2
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Boreas Reference Manual • Advanced Navigation Packet Protocol