Readfile writefile serial port

If part of a file is locked by another process and the read operation overlaps the locked portion, this function fails. Accessing the input buffer while a read operation is using the buffer may lead to corruption of the data read into that buffer. Applications must not read from, write to, reallocate, or free the input buffer that a read operation is using until the read operation completes.

This can be particularly problematic when using an asynchronous file handle. Additional information regarding synchronous versus asynchronous file handles can be found in the Synchronization and File Position section and in the CreateFile reference topic. Characters can be read from the console input buffer by using ReadFile with a handle to console input.

The console mode determines the exact behavior of the ReadFile function. For more information, see CreateFile. When reading from a communications device, the behavior of ReadFile is determined by the current communication time-out as set and retrieved by using the SetCommTimeouts and GetCommTimeouts functions. Unpredictable results can occur if you fail to set the time-out values. If the pipe buffer is full when an application uses the WriteFile function to write to a pipe, the write operation may not finish immediately.

The write operation will be completed when a read operation using the ReadFile function makes more system buffer space available for the pipe. For more information about pipes, see Pipes. File Management Functions. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode.

WriteFile function fileapi. Please rate your experience Yes No. Any additional feedback? For more information, see Remarks. In this article. In Windows ,. To find out the COM number corresponding to your serial port,. If you double click on COM24,you can see the details of the corresponding port. Windows10 Accounts. Opening and Closing a Serial Port. CreateFile is a Win 32 function which is used to create or open a file, stream or an IO device like serial port.

On success CreateFileA will return a handle which is then used to refer the connection in all subsequent operations.

After opening a serial port using the CreateFileA function you should close it with CloseHandle function, otherwise port will become unavailable to other programs. Now let's write a small program to open and close a serial port on Windows. To Configure the DCB structure we use two functions, GetCommState function which retrieves the current control settings of the serial port and SetCommState function which configures the serial port with the new values in DCB structure provided by us.

ReadIntervalTimeout Specifies the maximum time interval between arrival of two bytes. If the arrival time exceeds these limits the ReadFile function returns. ReadTotalTimeoutConstant is used to calculate the total time-out period for read operations.

For each read operation, this value is added to the product of the ReadTotalTimeoutMultiplier member and the requested number of bytes. ReadTotalTimeoutMultiplier is used to calculate the total time-out period for read operations.

For each read operation, this value is multiplied by the requested number of bytes to be read. After this you have to set the values using SetCommTimeouts function. Writing data to the opened serial port is accomplished by the WriteFile function.

Microcontroller Interface. The Controller waits for a character to be received and lights up the corresponding LED. The code for interfacing MSP is available in the Github repo. Here's a simple terminal program. It's minimalist in the extreme, but does work at least well enough to let me see output from my GPS, for one example. It's a long ways from what anybody least of all me would call sophisticated, but should give at least some idea of how to get started.

If you do not explicitly set the timeouts , then ReadFile will indefinitely block until data becomes available. ReadFile function may be blocking your thread,if so, it will remain blocked until some data can be read from Serial port. Here is a link see if its help. Good luck. I had this problem on a readfile, with the timeouts set. This was driving me crackers so I ended up getting some code from the web which did work and then changing line by line to see where the error was.

Turns out he readfile was fine. My problem was a WaitCommEvent which was hanging when the port was disconnected as no com event is ever received How are we doing? Please help us improve Stack Overflow. Take our short survey.