Chapter 3 SPAN Operation
OEM7 SPAN Installation and Operation User Manual v14
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DMI Update Logic
DMI data is available through the
RAWDMI
log. The
RAWDMI
log can be used for applying DMI updates in
post-processing.
The SPAN filter uses sequential
RAWDMI
logs to compute a distance traveled between update intervals (1 Hz).
This information is used to constrain free inertial drift during times of poor GNSS visibility. The filter also contains
a state for modeling the circumference of the wheel as it may change due to hardware changes or environmental
conditions.
Information about how the DMI updates are being used is available in the
INSUPDATESTATUS
log.
Connect the DMI to an Intermediate Processor
To connect a DMI:
1. Install the SPAN system components using the instructions in OEM7 Receiver Card Installation in the
OEM7 Installation and Operation User Manual
2. Connect the DMI to the intermediate processor. Refer to the DMI and processor user documents for more
information.
3. Connect the processor to one of the serial ports on the OEM7 receiver. Refer to Serial Ports in the
Installation and Operation User Manual
for information about the receiver serial ports.
4. Connect the 1PPS signal from the OEM7 receiver to an input on the intermediate processor. Refer to
EVENT_IN, EVENT_OUT and PPS Signal Protection in the
OEM7 Installation and Operation User Manual
for information about connecting the 1PPS signal.
5. Connect an external power supply to the DMI.
The power required for the DMI depends on the DMI used. Refer to the DMI user documents for more inform-
ation.
Configure the DMI
When using an intermediate processor, DMI data can be sent to the receiver as either accumulated wheel ticks
or current velocity.
Send Cumulative Wheel Ticks
The accumulated wheel ticks are sent from the intermediate processor to the OEM7 receiver using the
RAWDMI
command. This command must be sent once per update period (for example, once per second) and
contain the number of wheel ticks accumulated during that update period. Sending of the
RAWDMI
command
should be timed to the 1PPS signal from the receiver.
To configure the SPAN system to accept wheel ticks from an intermediate processor:
1. Send the following command to enable the DMI and set the expected input to wheel ticks.
DMICONFIG DMI1 ENABLE EXT_COUNT
2. Configure the intermediate processor to send a
RAWDMI
command to the OEM7 receiver once per update
period. This command provides the number of wheel ticks accumulated during this update period.
In the following example, 1000 wheel ticks have been accumulated on DMI1.
RAWDMI 1000 0 0 0 1
3. Send the following commands to log the DMI data available in the receiver.
LOG DMICONFIGA ONCHANGED
LOG RAWDMIA ONNEW