I have a simple application, which should send a single byte to a serial port once a minute. But sometimes, from some strange reason, it freezes somewhere in the WriteFile() function. Both sw and hw flow controls are turned off. I've googled some stuff about pending read operations performed from another threads, but I believe this is not a problem, because my app has single thread. Also, handle from CreateFile looks valid, so the port should not be used by any other applications. Have anybody suffered this?
A:
Well, I'm using this library: http://lhdelphi.ic.cz/uploader/storage/ComDrv32.pas in Delphi 7, on Windows XP, but the component inside is just a wrapper around some Win API calls, CreateFile, WriteFile, etc.
ComDrv32.pas doesn't appear to have a whole lot of thought put into error handling. It may work fine as long as things are going great, but there is no error checking on API calls. I wouldn't trust this library to be very robust.
Jozz
2008-10-30 23:36:30
+2
A:
If you google for the words writefile hangs, you'll find a number of discussions on this problem. Some leads are buffer overruns, sizing your buffer correctly, a defective COM port, clearing the status on error... Seems like there are plenty of things to try.
Another thing I would suggest is to use a communications library instead of calling the API directly, something like Async Professional (http://sourceforge.net/projects/tpapro/). Even if they add some overhead to your application, they might simplify your work and avoid a number of potential pitfalls...
Jozz
2008-10-30 22:54:16
A:
Have you tried setting CommPortDriver.CheckLineStatus to true ("to prevent hangs when not device connected or device is OFF")? The source for the comdrv32.pas library contains that suggestion.
Argalatyr
2008-10-30 23:16:50