Serial Port Complete - Latest Microcontroller projects

Chapter 10

The safest approach is to check before each write to a port to verify that the

transmit buffer has room for the data:

 Dim stringToWrite as String

stringToWrite = "hello, world"

' Find out if the transmit buffer has room for the new data.

If ((myComPort.WriteBufferSize - myComPort.BytesToWrite) > _

stringToWrite.Length) Then

myComPort.Write(stringToWrite)

Else

Console.WriteLine("Not enough room in transmit buffer.")

End If

 String stringToWrite;

stringToWrite = "hello, world";

// Find out if the transmit buffer has room for the new data.

if ((myComPort.WriteBufferSize - myComPort.BytesToWrite) > stringToWrite.Length)

{

myComPort.Write(stringToWrite);

}

else

{

Console.WriteLine("Not enough room in transmit buffer.");

}

Even writing a small amount of data can overflow the write buffer if previous

write operations have filled the buffer. A loop or timer routine can check for

room in the buffer at intervals and write the data when the buffer has room.

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As with read operations, each write operation adds overhead. To keep from

hanging the application, perform the write operations in a separate thread as

described above. Write large amounts of data in one operation or a series of

large blocks. Set WriteTimeout long enough to prevent timeouts under normal

conditions, including delays due to flow control.