DMU380ZA Series
User’s Manual
________________________________________________________________________
Doc# 7430-3810 Rev. 02
Page 6
NMEA*
GPGGA, GPVTG
4Hz
9600, 19200, 38400,
57600
*Not recommended for airborne applications.
**57600 is the preferred baud rate for optimum performance
The secondary UART port should be configured to 8 data bits, 1 start bit, 1 stop bit, no
parity bit, and no flow control.
2.1.4.1
1 PPS Input Interface
When using external GPS aiding for a VG/AHRS/INS380ZA system, Pin 2 should be
used for the 1PPS input signal to force synchronization of sensor data collection to a 1Hz
rising-edge signal. The signal must maintain 0.0-0.2 V zero logic and 3.0-5.0 volts high
logic and stay within 100ms of the internal system 1 second timing. Sending this signal
to the system will align the sensor data collection and algorithm processing to its rising
edge and 10ms boundaries thereafter. When the system is synchronized to 1PPS, the
hardwareStatus
unlocked1PPS flag will be zero; otherwise, it will be one.
2.1.4.2
SPI Com Synchronization Input
If the user does not have 1PPS available from an external GPS receiver, then Pin 2 can be
used as a sync pulse to force synchronization of sensor data collection to a 1 KHz rising-
edge signal for output over the SPI port.
2.1.4.3
External GPS Receiver Antenna Connection
The external GPS receiver needs to receive signals from as many satellites as possible. A
GPS receiver doesn’t work properly in narrow streets and underground parking lots or if
objects or human beings cover the antenna. Poor visibility may result in position drift or a
prolonged Time-To-First-Fix (TTFF). A good sky visibility is therefore a prerequisite.
Even the best receiver can’t make up for signal loss due to a poor antenna, in
-band
jamming or a poor RF cable. Placing the antenna on a 4 inch or larger ground plane is
highly recommended.
IMPORTANT
Place the antenna with optimal sky visibility and use a ground plane. Route the GPS
Antenna RF cable away from sources of radiated energy (i.e. switching power supplies).
2.1.5
Reserved
–
Factory Use Only
During normal operation of the DMU380ZA, no connection is made to the Reserved
–
factory use only pins. These pins have internal pull-up mechanisms and must have no
connections for the DMU380ZA to operate properly.
Mechanical Interface
2.2
The DMU380ZA mechanical interface is defined by the outline drawing in Figure 2.