Unimodem OS Design Development
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Windows Embedded CE provides Unimodem as a sample TSP. Unimodem provides access to most standard modems. You can also create a customized TSP by using the TSPI.
A service provider driver is a separate dynamic-link library (DLL) and not part of TAPI. The Unimodem driver translates TAPI function calls into AT-based modem commands to configure and dial modems. TAPI manages the use of devices, ports, and call traffic by the application.
Unimodem supports Hayes-compatible AT-command-based modems. To implement other media types, such as ISDN, you must create a customized TSP.
Unimodem also provides direct cable connect (DCC) support. DCC lets you establish a direct serial or parallel cable connection between two computers to share the resources of the computer that is designated as the host. If the host is connected to a network, the guest computer also can access the network.
You set the registry keys for a specific modem and Unimodem reads the registry keys and creates a line device for that modem. For example, when a PC Card modem is plugged in, Unimodem creates a line device for that modem.
For Unimodem, the memory region that is described by the dwDevSpecificOffset and dwDevSpecificSize members of the LINEGETDEVCAPS structure is a UNIMODEM_INFO structure, as defined in Unimodem.h. Also, the memory region that is described by the dwProviderInfoOffset and dwProviderInfoSize members contains the plaintext Unicode string UNIMODEM.
The Windows Embedded CE implementation of Unimodem does not support voice modems, but you can create a customized TSP that supports them.
The Windows Embedded CE implementation of Unimodem supports hardware flow control modems only. Unimodem traces the carrier detect (CD) signal to determine if a connection exists. For software flow control modems, Unimodem is unable to detect a line drop, so the connection must be detected and dropped by an upper-layer application, such as the Point-to-Point Protocol (PPP).