LORD MicroStain 3DM-GX5-45, Руководство Dcp

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3DM-GX5-45
™
GNSS-Aided Inertial Navigation System
DCP Manual
Once you have sorted the different packets and sent them to the proper packet handler, the packet
handler may parse the packet payload fields and handle each of the fields as appropriate for the
application. For simple applications, it is perfectly acceptable to have a single handler for all packet
types. Likewise, it is perfectly acceptable for a single parser to handle both the packet type and the
fields in the packet. The ability to sort the packets by type is just an option that simplifies the
implementation of more sophisticated applications.
2.6 Multiple Rate Data
The message format commands ( IMU Message Format and Estimation Filter Message Format ) allow
you to set different data rates for different data quantities. This is a very useful feature especially for
IMU data because some data, such as accelerometer and gyroscope data, usually requires higher data
rates (>100 Hz) than other IMU data such as Magnetometer (20 Hz typical) data. The ability to send
data at different rates reduces the parsing load on the user program and decreases the bandwidth
requirements of the communications channel.
Multiple rate data is scheduled on a common sampling rate clock. This means that if there is more than
one data rate scheduled, the schedules coincide periodically. For example, if you request
Accelerometer data at 100 Hz and Magnetometer data at 50 Hz, the magnetometer schedule
coincides with the Accelerometer schedule 50% of the time. When the schedules coincide, then the
two data quantities are delivered in the same packet. In other words, in this example, you will receive
data packets at 100 Hz and every packet will have an accelerometer data field and EVERY OTHER
packet will also include a magnetometer data field:
Packet 1 Packet 2 Packet 3 Packet 4 Packet 5 Packet 6 Packet 7 Packet 8 ...
Accel Accel
Mag
Accel Accel
Mag
Accel Accel
Mag
Accel Accel
Mag
Accel
If a timestamp is included at 100 Hz, then the timestamp will also be included in every packet in this
example. It is important to note that the data in a packet with a timestamp is always synchronous with
the timestamp. This assures that multiple rate data is always synchronous.
Packet 1 Packet 2 Packet 3 Packet 4 Packet 5 Packet 6 ...
Accel
Timestamp
Accel
Mag
Timestamp
Accel
Timestamp
Accel
Mag
Timestamp
Accel
Timestamp
Accel
Mag
Timestamp
Accel
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