GPRS module emulates wired modem

GPRS (General Packet Radio Service) capability is rapidly becoming widespread in the GSM (Global System for Mobile communications) network, making it an attractive option for data connections to applications for embedded systems. You may need to upgrade a low-speed dial-up modem to a higher data rate and take advantage of the GPRS "always-on" capability. Or, you may want to extend connectivity to a mobile application.

You can add the GPRS function as a drop-in module using AlphaMicro's dual-band wireless modem (Picture). The module integrates a RIM (www.rim.net) GSM/GPRS transceiver module with a host microcontroller that handles all the emulation of a conventional modem. Although the air interface is GPRS, the software stack that AlphaMicro has written to run on the microcontroller—which is an NEC part (www.nec.com)—allows you to address the modem using the standard AT command set.

The same module, measuring 90×56 mm, has a predefined site on its pc board for the addition of a GPS module—this time, a µ-Blox module (www.u-blox.com)—serving mobile applications that must report positions or be location-sensitive. Marketing manager Peter Smith says that one reason for using the RIM module is its good receiver sensitivity, which maintains communications out to the edge of cells in locations where GSM coverage is less comprehensive, such as in the United States. For areas that have GSM but not GPRS, the software "falls back" to the standard 9.6-kbps data-over-GSM service.

The company will market the complete module, as well as a loaded-ROM version of the NEC microcontroller, with the complete software stack, for users who wish to integrate their own systems. Designers completed a project to equip a point-of-sale system with a radio data link in four weeks. Smith estimates that you could complete a similar project without the preconfigured hardware and software in three to six months. The module, coded AMC1802GSXLA, will sell for around $150 (10,000).

AlphaMicro, 1-561-744-9986, www.alphamicro.net.