Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.arch.embedded > #28522

Re: Serial Port Emulation

Show all headers | View raw

On 19/02/2019 18:12, gnuarm.deletethisbit@gmail.com wrote:
> On Tuesday, February 19, 2019 at 11:10:16 AM UTC-5, Andrew Smallshaw wrote:
>> On 2019-02-18, David Brown <david.brown@hesbynett.no> wrote:
>>>
>>> RS-232 is short distance too (though a bit longer than TTL) - for long
>>> distances you use RS-485 or RS-422.  RS-232 is a legacy standard - there
>>> is plenty of old stuff the still has it, but it would be a strange
>>> choice for anything new.
>>
>> I'm genuinely interested to hear people thoughts on this.  Personally
>> if I anticipate a true long life interfacing requirement - 20, 30,
>> 40 years - RS232 is my preferred option, ideally (if appropriate
>> to the use case) with a command line on it.  My rationale has always
>> been that RS232 isn't going anywhere, terminal emulators are always
>> going to be around, so that combination makes fewest assumptions
>> about hardware or software.  Even if serial ports are no longer
>> standard equipment they'll always be easy enough to add and at
>> moderate cost.  The relative simplicity of the technology and the
>> simplicity of the host software makes me feel sure of that.
>>
>> It's also what's always made me feel slightly uneasy about USB.
>> In many ways it is a nice standard but it depends on quite a thick
>> layer of software on the host side.  If it falls out of favour and
>> support gets dropped over time re-adding that software layer is
>> problematic even if the hardware is to hand.
> 
> You raise some interesting points.  I don't know how easy it is to add RS-232 to a PC other than through a USB interface which adds back all those layers of software even if you don't need to deal with them.  The last RS-232 board I've seen was for the PCI bus which is no longer used in PCs.
> 

It is not hard to get RS-232 interface boards with PCI Express.  I have 
not seen one used, but they are reasonably easily available.  USB serial 
adapters are, however, the norm.

> Even so, desktops are waining and laptops are sold in much greater numbers.  I wouldn't design anything that required a desktop to work.  So I think you are stuck with USB either as the actual interface or an intermediate interface.
> 

By "USB" do you mean real USB, or using a USB-to-serial cable?  The 
challenge with a real USB connection is the software side - drivers and 
the like.  Even with software like libusb it is still a PITA.

> 
>> It may seem difficult to imagine now but I can see it coming - try
>> reading the original USB spec and seeing what a big play it makes
>> of the single cable with just one upstream and one downstream
>> connector.  Now there are so many possible combinations of port
>> and cable it makes parallel SCSI look posivitely straightforward.
>> And yes, I do see this creating confusion among non-technical users:
>> the original B plug has been poorly recognised for years, and I've
>> heard a few people recently see an A plug and respond along the
>> lines of "No, that's a charger plug, I need a _USB_ plug...".  Full
>> size A sockets are already disappearing from laptops, in a few
>> years someone is bound to drop USB entirely in favour of something
>> else to "improve" things for the consumer.
> 
> I think there is nothing any other interface can do better than USB other than possibly wireless.  USB is fast and stable and here for the long haul.  Heck, it has ramped up from 1.0 to 1.1, 2.0, 3.0, 3.1... what is going to replace it?  The type C connector is a significant improvement and with enough time will become the dominant interface although I think displacing the type A connector will take a long time.  As you say, it's a charger defacto interface.
> 

There are far too many "standard" USB connectors - especially when 
considering long-term systems.  Serial (be it TTL UART, RS-232, RS-485 
or RS-422) has a big advantage for connectors that it really doesn't 
matter.  You need three wires (5 for RS-422), and there are no issues 
with speed, impedance, or anything like that.  An RS-232 9-pin DSUB may 
be convenient, but any connector will work fine and can be jerry-rigged 
as needed.  And the various UART standards are simple, can be 
bit-banged, and just need a simple driver.  That is a big plus for 
long-lasting systems.

> 
>> The software issue is similar for the other hardware that I can't
>> see disappearing, namely ethernet.  Specific media may change in
>> popularity but you should be able to interface older stuff easy
>> enough, just as it still isn't _too_ difficult to track down a
>> 10Mbit hub with AUI and/ BNC connectors if you need modern stuff
>> to connect to coax.  My concern there it that we'll be transitioning
>> to IPv6 any decade now.  Realistically when is imposssible to
>> predict but I feel sure once a certain critical mass develops IPv4
>> will seem obsolete in 5-10 years.  If we use that in our though
>> processes large amount of equipment and plant may well not be even
>> halfway through its expected life when that timespan elapses.  Dual
>> stack is one possibilty but I'll admit I don't understand IPv6 well
>> enough yet and I don't like the sound of the complexity.
> 
> It's dual stack now.  There is nothing that will make IPv4 become inoperable.  Just as the routers hide the IP address of local devices, IPv6 can be used in the entire rest of the world and IPv4 can be used locally.
> 
> 
>> I don't pretend to have answers in the general case, just interested
>> in what peoples thoughts are.
> 
> I expect USB will survive for decades more even if only to interface to mice and printers.  In fact, newer laptops seem to have more USB connectors with many having four while the typical number used to be three.
> 

I too expect it to last for a good while yet.  But I expect UART 
connections to last a lot longer.

> I'm just glad the PCMCIA interface is gone.
> 

People Can't Memorize Computer Industry Acronyms?  I haven't seen one 
for a /long/ time.  But my usual computer parts supplier has a PCMCIA 
adapter with an RS-232 port on stock.


> Rick C.
> 

Back to comp.arch.embedded | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Serial Port Emulation gnuarm.deletethisbit@gmail.com - 2019-02-17 02:08 -0800
  Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-17 13:42 +0100
    Re: Serial Port Emulation Chris <xxx.syseng.yyy@gfsys.co.uk> - 2019-02-17 15:49 +0000
  Re: Serial Port Emulation Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2019-02-17 18:54 +0200
    Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-17 21:16 +0100
      Re: Serial Port Emulation Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2019-02-18 10:38 +0200
        Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-18 10:49 +0100
          Re: Serial Port Emulation Richard Damon <Richard@Damon-Family.org> - 2019-02-18 07:25 -0500
            Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-18 14:31 +0100
              Re: Serial Port Emulation Andrew Smallshaw <andrews@sdf.org> - 2019-02-19 16:10 +0000
                Re: Serial Port Emulation gnuarm.deletethisbit@gmail.com - 2019-02-19 09:12 -0800
                Re: Serial Port Emulation upsidedown@downunder.com - 2019-02-19 19:58 +0200
                Re: Serial Port Emulation Grant Edwards <invalid@invalid.invalid> - 2019-02-19 18:22 +0000
                Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-19 22:50 +0100
                Re: Serial Port Emulation Grant Edwards <invalid@invalid.invalid> - 2019-02-19 22:23 +0000
                Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-20 08:53 +0100
                Re: Serial Port Emulation upsidedown@downunder.com - 2019-02-20 10:17 +0200
                Re: Serial Port Emulation Theo <theom+news@chiark.greenend.org.uk> - 2019-02-19 22:35 +0000
                Re: Serial Port Emulation upsidedown@downunder.com - 2019-02-20 01:36 +0200
                Re: Serial Port Emulation gnuarm.deletethisbit@gmail.com - 2019-02-19 19:40 -0800
                Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-20 09:00 +0100
                Re: Serial Port Emulation upsidedown@downunder.com - 2019-02-19 19:16 +0200
                Re: Serial Port Emulation Theo <theom+news@chiark.greenend.org.uk> - 2019-02-19 22:28 +0000
                Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-20 10:32 +0100
                Re: Serial Port Emulation Robert Wessel <robertwessel2@yahoo.com> - 2019-02-19 18:44 -0600
                Re: Serial Port Emulation Les Cargill <lcargill99@comcast.com> - 2019-02-23 14:48 -0600
                Re: Serial Port Emulation Robert Wessel <robertwessel2@yahoo.com> - 2019-02-23 16:34 -0600
                Re: Serial Port Emulation Les Cargill <lcargill99@comcast.com> - 2019-02-27 22:15 -0600
                Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-02-28 08:41 +0100
                Re: Serial Port Emulation gnuarm.deletethisbit@gmail.com - 2019-02-28 15:07 -0800
                Re: Serial Port Emulation David Brown <david.brown@hesbynett.no> - 2019-03-01 10:04 +0100
                Re: Serial Port Emulation gnuarm.deletethisbit@gmail.com - 2019-03-01 13:09 -0800
                Re: Serial Port Emulation Les Cargill <lcargill99@comcast.com> - 2019-03-04 17:58 -0600
                Re: Serial Port Emulation Paul Rubin <no.email@nospam.invalid> - 2019-03-01 02:25 -0800
                Re: Serial Port Emulation gnuarm.deletethisbit@gmail.com - 2019-03-01 13:16 -0800
                Re: Serial Port Emulation Paul Rubin <no.email@nospam.invalid> - 2019-03-01 16:45 -0800
                Re: Serial Port Emulation Les Cargill <lcargill99@comcast.com> - 2019-03-04 17:44 -0600
                Re: Serial Port Emulation Richard Damon <Richard@Damon-Family.org> - 2019-02-23 19:37 -0500
                Re: Serial Port Emulation Les Cargill <lcargill99@comcast.com> - 2019-02-27 22:17 -0600
          Re: Serial Port Emulation gnuarm.deletethisbit@gmail.com - 2019-02-18 06:28 -0800
          Re: Serial Port Emulation Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-02-18 22:33 +0100
  Re: Serial Port Emulation "A.P.Richelieu" <aprichelieu@gmail.com> - 2019-02-17 21:06 +0100
  Re: Serial Port Emulation raimond.dragomir@gmail.com - 2019-02-17 21:56 -0800
    Re: Serial Port Emulation gnuarm.deletethisbit@gmail.com - 2019-02-17 22:37 -0800
  Re: Serial Port Emulation "Mat Nieuwenhoven" <mnieuw@zap.a2000.nl> - 2019-02-18 12:34 +0100

csiph-web