Not all equipment needs high-speed Internet access. Remote sensor monitors, remote controllers, weather stations, security systems, and similar devices can use standard phone lines to communicate with a distant computer. To simplify this type of connection, Saelig Company now offers developers an embedded "World Modem NET" module that operates at standard modem data rates from 300 to 56K bits/sec. The module includes a direct attachment arrangement (DAA) that lets it connect directly to the standard ring and tip telephone wires. The DAA provides 5 kV of isolation.

Communications between a local computer or embedded system rely on standard serial-port signals (TTL), an SPI, or an I2C interface. The module operates from either a 3.3V or a 5V power source at 65 mA (max). On the local side, a microcontroller or embedded system would use standard AT modem-control commands to configure and operate the modem module.

Because the module handles many protocols, such as User Datagram Protocol (UDP), Simple Mail Transport Protocol (SMTP), File-Transfer Protocol (FTP), and Hypertext Transfer Protocol (HTTP), among others, developers can quickly have an Internet-capable system attached to a dial-up phone line without any difficulty. Because a module handles all protocol details, a remote embedded system requires no special drivers to initiate a TELNET session. All you need is the phone number of a local Internet Service Provider where you have a dial-up account and and the server addresses, which you supply to the module via simple AT-type modem commands. When a command executes, World Modem NET automatically connects to the Internet, performs the task, and provides the user with results.

A World Modem NET module includes an ARM processor that manages the dialup-modem interface and a TCP/IP stack. You can bypass the TCP/IP stack if you choose, which lets the module operate as a standard fax modem.

Copeland communications manufactures the World Modem NET module and you can find a complete data sheet at tinyurl.com/yj8vjnj. Copeland also provides a programming manual for the AT command set at: www.copelandcommunications.com/pdf/WMNET_Manual.pdf. This manual provides a lot of details, but I couldn't find any programming examples that explain how to perform specific functions. The company has created a World Model II evaluation board, but the manual I reviewed did not include any examples beyond a basic Hypertext link to a board from a Windows-based PC.

To purchase boards, go to the Saelig Web site at www.saelig.com/product/MO002.htm. Prices starting at $US 93.65 (one) and drop to under $US 50 for quantities of 1000. You also can reach Saelig at +1-888-7SAELIG (toll free in the US). --Jon Titus