Motus Reference Manual
Page 36 of 146
Version 1.1
29/11/2019
unit from under-voltage, over-voltage and reverse polarity events. The protection
circuit shuts off power and automatically recovers the unit to full operation once the
fault is removed. Take care when running the unit close to its under-voltage lockout of
4.2 V because small voltage drops can engage the under-voltage shutdown and
potentially oscillate between the on and off state. It is recommended that the unit is
always run at 5 V or more to avoid issues associated with this.
10.5
Odometer
On ground vehicles, the use of an odometer input can greatly improve Motus’s
navigation and orientation solution during GNSS dropouts. With a high resolution
wheel encoder Motus can be used to navigate indoors with GNSS disabled altogether.
There are several different options for odometer installation which are listed below.
10.5.1
Factory VSS Signal
Most road cars since 1980 contain a VSS (vehicle speed sensor) signal that can be
wired directly into one of Motus’s GPIO pins. The vehicle should be taken to an
automotive electrician to perform the work.
To setup the odometer, the appropriate GPIO pin should be set to odometer input
using Motus Manager, see section 12.8.6. The odometer pulse length must then be set
either manually or automatically, please see section 11.8 for more information.
For more information on the GPIO signals and their requirements please see section
15.4.3.
10.5.2
OBDII Odometer Interface
For applications where it is undesirable to modify the vehicle or the system needs to
be used with multiple vehicles, the OBDII odometer interface may be a better solution.
OBDII is a vehicle diagnostic port standard and most vehicles from the mid 1990s
onwards contain an OBDII port in the drivers side foot well. Advanced Navigation
produces an OBDII odometer interface that plugs into this OBDII port and feeds Motus
with odometer data over the Auxiliary RS232 port, please see Illustration 19. These
units are priced at approximately AUD 500. Please contact Advanced Navigation sales
for more information.
Illustration 19: Advanced Navigation OBDII Odometer
