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The NovAtel GPS Receiver Modules
The GPS6185 supports all NovAtel OEM4-G2L GPS Receiver Modules. The OEM4-G2L
TM
is a
parallel 24-channel, dual-frequency or 12-channel, single-frequency receiver featuring a 60 mm x
100 mm form-factor and low power consumption. All OEM4-G2L cards feature position output,
real-time DGPS positioning, support for RTCA and RTCM messages, two serial ports and a USB
interface. The OEM4-G2L is configurable as a rover or base station and is designed for
embedded applications.
Communication to and from the receiver is performed through one or two serial channels that are
connected to onboard UARTs. The receiver’s primary serial port outputs navigation data and
accepts commands from the OEM application is always connected to the first UART on the
GPS6185. The secondary serial port on the GPS module can be directed to either the second
UART channel or to a connector to interface with external devices.
This manual is not intended to be a GPS handbook. For more information on the GPS receiver
module please refer to the chapter titled ”Additional Information”.
Antenna
An active antenna is required because its low-noise amplifier (LNA) boosts the power of the
incoming signal to compensate for the line loss between the antenna and the receiver. NovAtel
offers a variety of single and dual-frequency GPS antenna models. All include band-pass filtering
and an LNA. The GPS antenna you choose will depend on your particular application.
UARTs
GPS data is sent to the host from the receiver through standard 16C550 compatible UARTs. All
x86 operating systems will recognize and support this serial communication device. The
GPS6185HR uses its own onboard serial port and will not reserve serial port resources from the
system. The I/O base address and interrupt for this serial port can be flexibly set as described in
previous chapters of this manual.
After setting the base address and IRQ, you can use any communication software package or
terminal program to connect to your GPS6185HR UART. The oscillator frequency is 1.8432 MHz
or 14.7456 MHz. A reference for programming serial port UARTs can be found in the chapter
titled “Additional Information” at the end of this manual.
Only TXD, RXD, CTS and RTS lines of the UART are connected to the GPS receiver. The DTR
signal of the first UART is used to generate a GPS reset signal. A reset pulse will be generated
when the DTR signal transitions from asserted to de-asserted (MCR bit 0 transitions from 1 to 0).
USB
The OEM4-G2L receivers running firmware version 2.100 or higher, along with the accompanying
NovAtel USB drivers for Windows 2000 and Windows XP, provide three virtual serial ports over a
single USB connection using USB D(+) and USB D(-) signals. These three virtual serial ports,
identified by the GPSCard as USB1, USB2, and USB3, are available to existing Windows
applications which use COM ports to communicate (for example, HyperTerminal and
GPSolution4). The NovAtel USB drivers assign COM port numbers sequentially following any
existing ports on the PC. For example, if a PC has COM1 and COM2 ports, the NovAtel USB
drivers will assign COM3 to USB1, COM4 to USB2, and COM5 to USB3.
