Please note that detailed description about opening the serial port using CreateFileA is explained in the previous article. Please do not forget to close the Serial Connection after you have finished. One way to test out the code is to connect LED's to the serial port and observe. If you are using a DB9 hardware serial port, Please use an appropriate RS decoder chip or high value resistor.
Please remember to change the COM port number to the one corresponding to your System. Privacy Policy. All rights reserved. All trademarks and service marks are the properties of their respective owners. And you are always reading an old sample.
Beware that the scheme is brittle, you could turn the signal off pretty reliably back in the DOS. Now you've got a driver in between. You may well end up turning RTS off too late. Which risks getting a stale reading. An alternative is to startup a thread that just reads continuously. And have your main code just use the last value that it read.
The overhead is quite low, serial ports are slow. The first thing to do would be to check the return values of the calls to EscapeCommFunction. If the return value is zero , the call failed and you should use GetLastError to receive more error information. I use a free third party serial port emulator VPS.
Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 10 years, 11 months ago. Active 10 years, 1 month ago. Viewed 2k times. I want to do as follows: meter is continuously taking readings every few sec, but does not send any info until it is requested by the computer when computer is ready to receive info from meter, it requests it.
It does not accept info otherwise. Update: The underlying story is that I present a given luminance brightness on a display and then need the corresponding luminance reading. Community Bot 1 1 1 silver badge. Bill Simpson Bill Simpson 57 5 5 bronze badges.
If an error occurs, the value is zero; otherwise, it is one of the following values. If the function fails, the return value is zero. To get extended error information, call GetLastError. The WaitCommEvent function monitors a set of events for a specified communications resource. The calling process can use one of the wait functions to determine the event object's state and then use the GetOverlappedResult function to determine the results of the WaitCommEvent operation.
GetOverlappedResult reports the success or failure of the operation, and the variable pointed to by the lpEvtMask parameter is set to indicate the event that occurred. If a process attempts to change the device handle's event mask by using the SetCommMask function while an overlapped WaitCommEvent operation is in progress, WaitCommEvent returns immediately. The variable pointed to by the lpEvtMask parameter is set to zero.
For an example, see Monitoring Communications Events. Communications Functions.
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