Is it possible to use python to get True Full Duplex on a Serial port?

John Nagle nagle at
Sun Aug 16 08:20:34 CEST 2009

Hendrik van Rooyen wrote:
> On Saturday 15 August 2009 14:40:35 Michael Ströder wrote:
>> Hendrik van Rooyen wrote:
>>> In the past, on this  group, I have made statements that said that on
>>> Linux, the serial port handling somehow does not allow transmitting and
>>> receiving at the same time, and nobody contradicted me.

     Absolutely false.

>> Despite all the good comments here by other skilled people I'd recommend to
>> determine whether the transmission line to the devices accessed support
>> full duplex.

     All standard PC serial ports are full-duplex devices.

     Here's a program I wrote which uses "pyserial" to drive Baudot teletypes
as full-duplex devices.

This uses an input thread and an output thread.  It reads RSS feeds and
prints them on antique Teletype machines.  (Reuters RSS feeds produce
a classic news ticker.  Twitter RSS feeds work but look silly when
hammered out on yellow paper at 45.45 baud.)
> You raise a good point, that is probably not well known amongst the youngsters 
> here, as simple serial multidropping has gone out of fashion.

     Actually, no.  Dynamixel servos as used on the latest Bioloid robots
are multidrop serial RS-485.  But outside the embedded world, nobody uses
that stuff any more.  (Embedded is going Ethernet; it's overkill but
works fine and is now cheap.)

					John Nagle

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