Implementing serial communication with API functions

The previous DOS system provides the ability to communicate with a serial interface via DOS interrupts and BIOS interrupts. In the Windows environment, the development tools of C + + do not provide specific serial communication control methods like DOS and BIOS, nor allow users to directly control the interruption of the serial port.

In order to ensure resource sharing, Windows system completely takes over all kinds of hardware resources, and the use of interrupts to control the port will destroy the system's multitasking and cause the stability of the system to be affected. However, Windows also provides powerful API functions that enable users to control serial communications indirectly.

1, realize the serial communication related API function

API functions not only provide an operational method for opening and reading communication ports, but also provide a variety of functions to support the various operations of serial communication. Common functions and roles are shown in table 5-1.

Table 5-1 common serial communication API functions and their functions

Function name function

CreateFile Open the serial port

Getcommstate Detection serial port settings

SetCommState Set serial port

BUILDERCOMMDCB fills a device control block with a value in a string

Getcommtimeouts Detection Communication Timeout setting

SetCommTimeouts Set Communication Timeout parameter

Setcommmask set up monitored events

Waitcommevent waits for the monitored event to occur

WaitForMultipleObjects waits for the results of multiple monitored objects

WriteFile Send data

ReadFile Receive data

GetOverlappedResult returns the result of the last overlapping (asynchronous) operation

PurgeComm empty the serial port buffer and exit all related operations

Clearcommerror updates the serial port State structure and clears all serial port hardware errors

CloseHandle Close serial port

2, open the serial port

The function CreateFile was originally used to open a file, but it is also available to open a communication port. As with other objects in the system, the communication port is also identified by a handle. The CreateFile function returns the handle of the communication port being manipulated, and the method is invoked as follows:

HANDLE CreateFile (