Navigation, tracking and localization applications are nowadays hot topics. Making the corresponding devices smaller and cheaper is just as important. In this regard, a couple of modules have been launched on the market that embed not only a full-fledged GSM modem and a GPS receiver, but are also equipped with a microcontroller that integrates and optimizes the two technologies. This considerably saves procurement costs and shortens development times. This article considers and compares three product series: Cinterion XT65 / XT75, Telit GM662 / GE863 and Unitronic Uni QuadNav. They have in common:
• a full-fledged QuadBand (850, 900, 1800, 1900 MHz) GSM/GPRS modem for worldwide deployment,
• a comprehensive Internet Protocol implementation,
• a set of general purpose (GPIO) and standard interfaces (among others IC, SPI, UART, USB),
• an ADC und sometimes a DAC,
• a real-time clock, and
• hardware and software development environments with reference projects.
They also offer the opportunity to update their firmware over-the-air and to manage a their energy-saving modes.
Cinterion Wireless Modules: XT65 / XT75
Siemens Wireless Modules has been renamed Cinterion Wireless Modules in June 2008. Cinterion, a German company, offers two modules: the base-module XT65 and the EDGE-extended XT75. They both have the most powerful GPRS modem (class 12). The GPS receiver is based on a u-blox Antaris 4 ATR0621 chipset, still a very good one though a bit obsolete (2005). The chipset supports an OMA SUPL compliant A-GPS receiver, even though no free SUPL server is offered and just scarce reference sources document this feature.
The EDGE-extended wireless module XT75
The modules have a microcontroller with an ARM processing core inside. They are the only modules equipped with a digital audio interface. The digital signal processing, intended for digital audio measurement and PCM data transmission, is performed by an Analog Devices Blackfin DSP. The programming language is Java Information Module Profile - Next Generation, a subset of Java J2ME MIDP 2.0 without graphical user interface support. The integrated RIL (Radio Interface Layer) driver provides a connection to Microsoft Windows Mobile based user devices.
The modules have at their disposal a powerful hardware and software development environment. The Eclipse-based development environment with meaningful reference designs is particularly noteworthy. Documentation is difficult to retrieve, but is rich and of good quality. Other noteworthy features are definitely the best hardare and software USB support, an integrated LNA (low-noise amplifier) for the GPS signal and the opportunity to connect both GSM and GPS
signals through either a U.FL connector or a soldering pad.