The Rockwell Zodiac™ Development Kit is designed to facilitate the evaluation of Rockwell's "Jupiter" Global Positioning System (GPS) receiver engine, which is based on the Zodiac chip set. This kit allows for the receiver to be used in both static and mobile operations for evaluation purposes.
Function Description:
The Development Kit implements the receiver control operation and input/output (I/O) functions of the GPS receiver. It interfaces with an IBM-AT compatible personal computer (PC) via a serial port, and requires an external antenna and power supply. The GPS receiver itself is housed in an enclosure that includes I/O connectors, status LEDs, and configuration DIP switches.
The kit includes LABMON, a GPS monitor and controller software, which runs on the PC. LABMON enables users to control the receiver and display its output message data. It also supports logging of externally supplied Radio Technical Commission for Maritime Services (RTCM SC-104) data using a second PC serial port, if desired. The LABMON software source code is provided as a reference for Original Equipment Manufacturer (OEM) code implementations.
The Development Kit features dual RS-232 level serial data I/O ports, selectable bias voltages for active GPS antennas, various port configurations, and message protocols. It also offers flexible internal "Keep-Alive" back-up power modes for both the Static Random-Access Memory (SRAM) and the low-power time source. The kit contains the necessary circuitry to convert the receiver's Complementary Metal Oxide Semiconductor (CMOS) level output to RS-232 level serial data I/O.
The two serial data ports are RS-232, 9-pin D-Subminiature connectors. The first, or "host" serial port, is used for sending and receiving both binary and National Marine Electronics Association (NMEA-0183) initialization and configuration data messages. The second, or "auxiliary," I/O port is dedicated to the reception of RTCM SC-104 Differential GPS (DGPS) correction messages, with no data output from the receiver through this port.
An auxiliary output connector on the Development Kit provides access to the 1 pulse-per-second (1 PPS) time mark and 10 KHz time mark signals. These signals are buffered CMOS level outputs driven by a 74LS04 CMOS inverting buffer device and can be used by the OEM's processor for synchronization.
Important Technical Specifications:
- Power Input: DC power for the Development Kit is supplied by either an AC/DC converter (nominal 120 VAC @ 60 Hz input, 12 VDC @ 500 mA output) or an automotive adapter (for 12V vehicles).
- Antenna Bias: The active antenna supplied with the kit requires a +5 VDC bias. The kit supports selectable antenna bias voltages of 0, +5, or +12 VDC for active antennas.
- Serial Ports: Dual RS-232, 9-pin D-Subminiature connectors.
- Host Port Protocol: NMEA-0183 (4800 bps, no parity, 8 data bits, 1 stop bit) or Rockwell Binary (9600 bps, no parity, 8 data bits, 1 stop bit) depending on switch settings.
- Output Signals (Auxiliary I/O):
- K10: Buffered 10 KHz UTC output frequency reference signal (synchronous, 50 ±5 percent duty cycle).
- TM: Inverted version of TM_F Pulse (1 PPS CMOS output signal, buffered through a 74LS04 device).
- Backup Power: The "Jupiter" receiver engine includes an onboard Super Capacitor (Supercap) that provides backup power to the SRAM and RTC devices for at least one hour after primary power is removed. External backup voltage can also be supplied to the RTC for "warm start" capability.
- PC Requirements: IBM-AT compatible PC processor with at least one available serial port, a 3.5-inch diskette drive, at least 640 KB RAM, and DOS version 3.0 or greater. A color monitor with VGA or EGA, or monochrome monitor with VGA (no monochrome with EGA) is required.
Usage Features:
- Configuration: The "Jupiter" board is configured using a bank of eight DIP switches, three jumper blocks, and a single, two-position jumper switch block. These settings control antenna bias, output message protocol, EEPROM enable/disable, I/O signal control, RTC control, and preamp voltage/power.
- Antenna Connection: A magnetic mount, active antenna with an 8-foot long RF cable (RG-316) and SMA connector is supplied. Users must ensure antenna power switches are correctly set (+5 VDC for the supplied antenna) before connecting the antenna to prevent damage.
- DGPS Operation: Requires an RTCM data source and appropriate cabling to connect to the receiver's Auxiliary port. For simultaneous RTCM SC-104 data collection and DGPS operation, a three-connector cable is recommended to connect the RTCM source to both the Development Kit's Auxiliary port and an unused serial port on the PC.
- Status Indicators: Four front panel LEDs provide basic status: POWER (illuminates when power is applied), TIME MARK (flashes at 1 Hz when receiver is operating), NMEA ASSURED (illuminates when NMEA protocol is selected for the Host port), and DGPS ACTIVE (illuminates when data is received by the Auxiliary port, but does not indicate data integrity or receiver mode).
- Reset Functionality: A momentary pushbutton switch on the Development Kit board generates a master reset signal to the receiver. A pushbutton ON/OFF power switch controls primary power to the "Jupiter" board.
- Portability: A laptop or portable PC is highly recommended for outdoor evaluation where GPS signals are more accessible.
Maintenance Features:
- Power Monitoring: Jumper blocks allow OEMs to insert a current measuring device inline with the primary and Real-Time Clock (RTC) power lines to monitor power usage.
- Receiver Isolation: An electronic bus switch, controlled by a DIP switch, isolates the receiver from the Development Kit and controls the bus voltage level.
- Test Pins: A number of test pins on the Development Kit board provide access to I/O signal lines at CMOS levels, located before the RS-232 drivers and timing reference signal buffers.
- ESD Precautions: If the Development Kit cover is removed for configuration, proper Electrostatic Discharge (ESD) precautions must be observed to prevent damage to circuits.
- Antenna Placement: For optimal reception, the GPS antenna should be placed where the view of the sky is least obstructed. GPS signals are severely attenuated or totally obscured by various building materials and coated glass.
- RTCM Data Integrity Check: A utility program, RTCMCHK, included on the LABMON disk, checks the integrity of RTCM SC-104 data sources.
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