DMU380SA Series
User’s Manual
________________________________________________________________________
Doc# 7430-0026 Rev. 01
Page 6
Table 5.
Configuration of An External GPS Receiver for VG380SA/AHRS380SA
Protocols
Required Messages
Required Message Rate
Baud rate
Ublox binary
NAV-LLH, NAV-VELNED,
NAV-STATUS
4 Hz
9600, 19200, 38400,
57600$
NovAtel OEM4 and
OEMV Binary
BestPosB, BestVelB
4Hz
9600, 19200, 38400,
57600$
NovAtel OEM4
ASCII
PosVelNavDopA
4Hz
19200, 38400, 57600$
NMEA*
GPGGA, GPVTG
4Hz
9600, 19200, 38400,
57600$
*
Not recommended for airborne applications.
$
57600 is the preferred baud rate for optimum performance
The GPS serial communication port should be configured to 8 data bits, 1 start bit, 1 stop
bit, no parity bit, and no flow control.
1 PPS Output Interface (INS380SA)
2.7
The 1PPS output signal on pin 8 is provided by the internal GPS receiver (when GPS
timing is known) on INS380SA products. The 1PPS output signal is open-collector and
should be interfaced to a rising-edge trigger with pull up resistor between 1k and 10k
ohms
.
The INS380SA Series products synchronize sensor data collection to this 1PPS
signal internally when available. Therefore, the 100Hz navigation algorithm will run
exactly 100 times each second with no slip when locked to 1PPS. Packet data is valid on
the rising edge of 1PPS and 10ms boundaries thereafter. There is, however, up to 500µs
of additional latency in sensor data collection. If 1PPS is provided by the internal GPS
receiver in NAV products, then the rising edge of 1PPS will correspond to the UTC
second boundary. When the system is synchronized to 1PPS, the
hardwareStatus
unlocked1PPS flag will be zero, otherwise, it will be one.
Figure 2 shows the sequential order of the signal present at 1 PPS OUT pin.
The 1 PPS signal is aligned to the sampling clock of 23.104 MHz. This results in a timing
resolution of 43 ns.
Figure 2.
1PPS Output Signal
Sync Pulse Input Interface (IMU, VG, and AHRS380SA)
2.8
The Sync Signal Input signal allows the user of IMU, VG, and AHRS 380 products to
force synchronization of sensor data collection to an external synchronization signal (1
KHz). The signal must maintain 0.0-0.2 V zero logic and 3.0-5.0 volts high logic.
