🚀 go-pugleaf

> I have created my own com port class and have had no problems
transmitting
> and recieving data via my serial ports, but now I want to control
the RTS
> line as a direction control pin for RS485 data.
Unfortunately there isn't an easy solution to that problem. I've been
looking for years...

> Unfortunately, the WaitCommEventFunction returns immediately
That's because the serial _software_buffer_ is empty, but you don't
know the state of the hardware buffer and shift register (where the
bits are really output).

> I cant use the fRtsControl from the DCB structure as it drops the
line upto
> 10 ms after the data has been sent and is not fast enough.
Not fast enough? Mmm... you could think to introduce a delay in your
485 device (provided that you are developing it of course).

There are two "best solutions": using an automatic 232/485 converter
(you don't need to move any signal any more) or creating your own
serial driver. The latter is surely difficult, but you could access
the COM port at low level (such as we did under DOS, where you can
check the state of the shift register and you didn't have any problem
handling 485).

Another solution (simpler, but not perfect) is to send one character
per time or add a final dummy character at the end of the string (if
this doesn't introduce protocol problems). Also, try setting different
values for the COM port transmission buffer (see in the control
panel).

If you find any better solution let me know.

HTH,

Steve.