User's Manual

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EHS8 Hardware Interface Overview Page 23 of 43

 EHS8_HIO_v02.770 2014-08-11

Confidential / Preliminary

2.3 GPS Interface

2.3.1 GPS Receiver

EHS8 integrates a GPS receiver that offers the full performance of GPS technology. The GPS

receiver is able to continuously track all satellites in view, thus providing accurate satellite

position data.

The integrated GPS receiver supports the NMEA protocol via ASC0 interface. NMEA is a

combined electrical and data specification for communication between various (marine)

electronic devices including GPS receivers. It has been defined and controlled by the US based

National Marine Electronics Association. For more information on the NMEA Standard please

refer to http://www.nmea.org.

Depending on the receiver’s knowledge of last position, current time and ephemeris data, the

receiver’s startup time (i.e., TTFF = Time-To-First-Fix) may vary: If the receiver has no

knowledge of its last position or time, a startup takes considerably longer than if the receiver

has still knowledge of its last position, time and almanac or has still access to valid ephimeris

data and the precise time.

2.3.2 GPS Antenna

In addition to the RF antenna interface EHS8 also has a GPS antenna interface. The GPS

installation is the same as for the RF antenna interface, except for pad 224 instead of pad 59.

It is possible to connect active or passive GPSS antennas. For active antennas the power is

supplied by ANT_GPS_PWR; see sample application given in

Figure 6. In either case the

antennas must have 50　 impedance. The simultaneous operation of GSM and GPS has

been implemented.

2.4 Sample Application

Figure 6 shows a typical example of how to integrate a EHS8 module with an application.

Usage of the various host interfaces depends on the desired features of the application.

Because of the very low power consumption design, current flowing from any other source into

the module circuit must be avoided, for example reverse current from high state external control

lines. Therefore, the controlling application must be designed to prevent reverse current flow.

Otherwise there is the risk of undefined states of the module during startup and shutdown or

even of damaging the module.

Because of the high RF field density inside the module, it cannot be guaranteed that no self

interference might occur, depending on frequency and the applications grounding concept. The