Dietmar Budelsky - 2003-11-24

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Hello,

when I read your demand, I remembered the work at my last
company with such a feature. To say it simple: forget about
it. The change of the RTS/CTS signal is inherited from the first
RS232<->RS485 converter available and many producers of
converter hardware made it "hardware compatible" to that
thing (a huge iron block). The Win32 driver allows for semi
duplex data transfer, but only with the correct RS232 flanks.
There is an API event to control the RTS signal directly, but
the flush signal, when the last character is sent to the
converter is coming asynchronous, so for most protocols the
manual API flow control is much too slow and unreliable (
after installing the Win 98 plus! packet, fast mouse
movements crashed communication, for example) . We tried
to access the serial hardware directly, as the standard
chip (16550?) is generating an interrupt when all chars are
sent, but capitulated when we found out that modern laptops
do not try to emulate the old separate serial chips but deliver
their own Windows software driver for their proprietary
hardware. We spent man months on that only to find it
be a dead end. Much easier to add a not gate to your
hardware.

Best regards

Dietmar