GNSS Compass Reference Manual
Page 44 of 85
Version 1.1
13/01/2021
10.4
Packet Acknowledgement
When configuration packets are sent to GNSS Compass, it will reply with an acknowledgement
packet that indicates whether the configuration change was successful or not. For details on the
acknowledgement packet, see section 10.9.1.
10.5
Packet Rates
The packet rates can be configured either the web interface for Ethernet variants, GNSS Compass
Manager for serial variants or through the Packets Period Packet. By default GNSS Compass is
configured to output the System State Packet at 20Hz.
10.6
Baud Rate
This section applies to the serial variant only and can be ignored for the Ethernet variant.
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 is the
packet length add five to account for the packet overhead. For example to output the system state
packet at 20Hz the calculation would be:
Data throughput = (100 (packet length) + 5 (fixed packet overhead)) * 20 (rate)
Data throughput = 2100 bytes per second
Minimum baud rate = data throughput x 11 = 23,100 Baud
Closest standard baud rate = 38,400 Baud
When multiple packets are set to output at the same rate, the order the packets output is from
lowest ID to highest ID.
10.7
Packet Timing
Packets are output in order of packet ID from lowest ID to highest ID and all packets that are
output in one sequence have their data matched to the same time of validity. The time of validity
can be found in either the System State Packet, the Unix Time Packet or the Formatted Time
Packet. For example if the Unix Time Packet, Status Packet and NED Velocity Packet packet were
all set to output at 10 Hz, at each 0.1 second period the three packets would output consecutively
by order of packet ID with all data synchronised between them and the Unix Time Packet providing
the time of validity for the other two packets.
10.8
Packet Summary
Packet ID
Length
R/W
Name
System Packets
0
4
R
1
-
W
2
1
R/W
3
24
R
