The GPS Wildcard^TM

Add Global Positioning System Capability to Your Instrument

The GPS Wildcard tracks your instrument anywhere on the globe. Now you can design a mobile instrument that knows exactly where it is and how fast it is moving by accessing signals from Global Positioning System (GPS) satellites. Your application program can read the current latitude, longitude, altitude, speed, course heading, time, and date. In addition, the GPS Wildcard software reports position error estimates, GPS fix quality, and the number of satellites in view and in use to enable real-time diagnostics. This tiny 2" by 2.5" board is a member of the Wildcard™ series that connects to Mosaic controllers.

GPS Hardware

The key component of this Wildcard is the GPS-15 subsystem manufactured by Garmin, the industry leader in GPS instrumentation. It implements a 12-channel GPS receiver, and includes a rechargeable backup battery to maintain the contents of the subsystem’s clock and memory for up to 21 days in the absence of external power. For good signal reception, the GPS subsystem includes a connection for a remote-mounted active antenna; this antenna accessory is available from Mosaic.

The GPS subsystem outputs standard NMEA (National Marine Electronics Association) data strings, called "sentences". Each sentence reports information about one or more GPS parameters such as location, speed, heading (direction), time, or position error estimates. A "frame" of 6 to 7 sentence types is output each second at 4800 baud by the subsystem and is processed by the on-board UART chip.

The data is read over the Wildcard bus interface by the host processor (QCard, QScreen, Handheld, or PDQ series controller). The 3.3 volt supply that runs the GPS receier can be shut down while not in use to conserve power.

Pre-Coded Drivers Extract GPS Data

Mosaic’s device driver functions make it easy to access the GPS data. The functions automatically parse the GPS NMEA sentences, extract the data fields, and store them in a data structure for your application program. A demonstration program illustrates how to use the GPS Wildcard in a multitasking application to print a formatted summary of all the GPS information.

Using the GPS Wildcard and its pre-coded software makes it easy to create unique location-aware mobile instruments.

GPS Wildcard Specifications

Receiver:	Garmin GPS-15 12 channel receiver
Warm Acquisition:	About 15 seconds
Cold Acquisition:	About 45 seconds
Sky Search Acquisition:	5 minutes
Update Rate:	One NMEA-0183 frame/second
Position Accuracy:	<15 meters, 95% typical
Velocity Accuracy :	0.1 knot RMS steady state
Current Draw:	Current Draw 200 mA @ +5V
Required Active Antenna (available from Mosaic):	10-40 dB gain, MCX male connector, noise < 7 dB, powered from the GPS module

Documentation

GPS Wildcard Manual (html) | (pdf)