-22 Oct 96  19:27:00-
=Charles Gaefke babbled to All about DosDevIOCtl for COM ports=

 CG> A) what INCL_xxxx lines do I need?  

I find it much simpler to #define INCL_BASE.  That way you don't have to
remember :)

 CG> B) Could someone explain to me the "best" way to open a
COM port for
 CG> reading  and writing?

With the sharing mode OPEN_SHARE_DENYREADWRITE.  Access should be passed
to child processes by passing the handle returned by DosOpen.

 CG> C) For DosDevIOCtl, would someone explain, in detail (if at all
 CG> possible) what the ParmList is, and how/when to use it.. what the
 CG> DataArea is, and how/when  to use it, what the ParmLengthMax,
 CG> DataLengthMax, DataLengthInOut, and  ParmLengthInOut are, and how to
 CG> use them.   
 
Look for Ray Gwinn's SIO driver.  It contains full documentation for
the IOCtl functions relavant to asynchronous communications.

 CG> Also, just to make sure, a "word" is an "int"
or "short", correct?

unsigned short int

 CG> And a "dword" is a "long", correct?

unsigned long int
which is basically the same as
unsigned int
if you're using a 32-bit compiler.

 CG> And a "byte" is a "char", correct?

unsigned char

 CG> If above is correct, then ParmLengthMax would be 5 ("dword" is 4
 CG> bytes +  "byte" which is 1 byte).  What about DataLengthInOut,
 CG> ParmLengthInOut, and  DataLengthMax?

Use sizeof().

 CG> And if a port is "locked", do you have to
"unlock" it before you
 CG> can  change the rate, then do you have to "relock" it?

That is the concept of "locking" :)

Mike Phillips
INTERNET:  phil4086{at}utdallas.edu


... ELECTRICIANS check your shorts.  
--- FMail 1.0g