9. Serial Communications

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Chapter 9. Serial Communications

Serial communications can be used to communicate to many different types ofdevices, from servers and minicomputers through to desktop PCs and GPS devices. Most of the time serial communications uses an RS232 serial port, and nearly all Windows CE devices have such a port. Other devices, such as some PCMCIA cards, use serial communications to transfer data using a virtual communications port rather than an RS232 port. Serial communications can also be used to transfer data between infrared ports.

Serial communications is being used less and less for communicating between Windows CE devices and other compfuters, since Point to Point Protocol (PPP) is used across an RS232 connection, and PPP allows TCP/IP communications techniques (see Chapter 8) to be employed. This is advantageous, since multiple applications using TCP/IP can communicate using a single connection, whereas with ordinary serial communications only a single application can use the port at any one time.

You can use RS232 communications techniques to initiate and manage a call through a modem using standard AT-type modem commands. It is, however, much easier to use TAPI (Telephone API) and RAS (Remote Access Services) to manage such connections, and this is described in Chapter 10.

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