So you have an RS-422 device connected to an RS-422 port?
If the port supports both RS-485 and RS-422 operation, then you probably have
to do something to control which mode it operates in. If it is in RS-485 mode,
it will do half duplex communication on one differential pair, and ignore the
other pair. Likewise for your "RS485 device".
--- In Jim Jackson <> wrote:
>
>
>
>
> On Fri, 4 Jun 2010, Harold wrote:
>
> > What do you mean by "single device is connected full duplex"? That does
> > not make sense. Full duplex means that it can transmit and receive at the
> > same time, which means it has separate transmit and receive connections.
> > RS-485 uses the same differential pair for both transmit and receive, in
> > half duplex, doing one at a time. It is not possible to connect an RS-485
> > device to an RS-485 port full duplex.
>
> The TS7260 option provides a diff pair for TX and a diff pair for RX on
> /dev/ttyAM1 (COM2). I have a device which has similar - the TX pair of one
> is connected to the RX pair of the other.
>
> You are probably saying that this is not proper rs485. Fine, sorry for
> using the wrong terminology.
>
> So rephrasing, is anybody using the rs485 option on the TS7260 in this
> mode?
>
> Can they verify that programmatically one can just treat it as a normal
> full duplex serial connection?
>
>
>
> >
> > Usually you can set up an RS-485 port so that it defaults to receive
> > mode, and automatically switches to transmit mode only while it is
> > transmitting, then switches back to receive mode when it is done
> > transmitting. But I have never used an RS-485 port on a TS-7260, so I
> > cannot say how it works there.
> >
> > Most often, RS-485 communication problems are due to incorrect wiring,
> > since everyone seems to use different pinouts.
> >
> > --- In Jim Jackson <jj@> wrote:
> >>
> >>
> >>
> >> I'm trying to speak to a single RS485 device connected to the second port
> >> of a TS7260 with the RS485 option.
> >>
> >> I've never dealt with rs485 before. Am I right in thinking that, if a
> >> single device is connected full duplex, then I should just treat,
> >> programming-wise, the interface as if it was an rs232 port?
> >> 'cos I've done that and am getting nothing. I'm getting the guys that did
> >> the hardware to double check their wiring to the COM2 header.
> >>
> >> If any RS485 expert could give any hints/advice it would be much
> >> appreciated.
> >>
> >> Jim
> >> p.s. the rs232 code works fine on /dev/ttyTS0 (com3) and on the serial port
> >> of my development machine.
> >>
> >
> >
> >
>
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