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Groups > comp.sys.raspberry-pi > #9687

Re: Something like a KVM switch for multiple Raspberry Pis

From rickman <gnuarm@gmail.com>
Newsgroups comp.sys.raspberry-pi
Subject Re: Something like a KVM switch for multiple Raspberry Pis
Date 2015-09-19 11:31 -0400
Organization A noiseless patient Spider
Message-ID <mtjv1d$8fd$1@dont-email.me> (permalink)
References (1 earlier) <mtemn9$vb3$1@disneywizard.eternal-september.org> <mth0l1$rsn$1@dont-email.me> <mthlv2$gsq$1@dont-email.me> <mthne9$pjl$1@dont-email.me> <mthnrp$s5k$1@dont-email.me>

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On 9/18/2015 3:17 PM, James Harris wrote:
> "rickman" <gnuarm@gmail.com> wrote in message
> news:mthne9$pjl$1@dont-email.me...
>> On 9/18/2015 2:42 PM, Martin Gregorie wrote:
>
> ....
>
>>> Put that way, it sounds very like an RPi with USB keyboard+mouse + HDMI
>>> monitor plus an Ethernet hub/switch connecting all the RPIs together.
>>>
>>> Use the one with keyboard etc to login to the other headless RPis.
>>
>> Exactly.  Unless there is some advantage to having a device on the pi
>> that actually plugs into the HDMI/USB connectors to emulate the
>> physical devices.
>
> Sure. Remote desktop or VNC etc can only work on a running OS and, what
> is more, a running OS which has suitable apps. For bare-metal
> programming, OS development and to see what's happening in the boot
> process you need access to the real inputs and outputs.

I'm divorcing from the follow on conversation and addressing this part.

Here is a block diagram of what I am reading is needed.

rPi
------+
  USB  |----- Keyboard
  USB  |----- Mouse
  HDMI |----- Monitor
  Pwr  |---------------Wall wart
  Eth  |---+
------+   |
           |
           |   +-------+ keyboard +-----+
           |   |       |----------|     |
           +---| Eth   |  mouse   |     |
               | Thing |----------| rPi |
           +---| Eth   |   HDMI   |     |
           |   |       |----------|     |
           |   +-------+          +-----+
           |
           |   +-------+ keyboard +-----+
           |   |       |----------|     |
           +---| Eth   |  mouse   |     |
               | Thing |----------| rPi |
           +---| Eth   |   HDMI   |     |
           |   |       |----------|     |
           |   +-------+          +-----+
           |
           |   +-------+ keyboard +-----+
           |   |       |----------|     |
           +---| Eth   |  mouse   |     |
               | Thing |----------| rPi |
           +---| Eth   |   HDMI   |     |
           |   |       |----------|     |
           V   +-------+          +-----+

I think this is what we are describing.  A main rPi (or some other 
device such as a PC) with a real keyboard, mouse and display connects 
via Ethernet to a series of "things" which provide the emulated mouse, 
kayboard and HDMI signals to a collection of rPi (or even other 
devices).  The main computer requires special software to drive the 
"things" via the Ethernet and the "things" will be some special hardware 
which responds to the commands and emulate the three I/Os.

I didn't draw the power because that is not clear to me if it is 
intended for the "thing" to channel power to the rPi or if the rPi will 
power the thing.  Since the keyboard/mouse will be plugged into at least 
one USB port, the rPi would power the "thing".

I don't see a need for a special "thing" on the head computer which has 
the physical keyboard/mouse/monitor attached.  This unit is just a 
computer with special software.  The "things" will need a slave USB port 
and an HDMI port to emulate a monitor, so I think that will require some 
special hardware.  I am not familiar with the HDMI spec, so I don't know 
exactly what will be required for that.  But otherwise, this will be not 
too much different from an rPi needing enough of a CPU to handle two 
Ethernet ports and being able to shuttle the HDMI graphics around.

I drew the Ethernet as a daisy chain.  Perhaps that should use a 
conventional star configuration with a hub/switch instead.

Another I/O that might be useful is something to force a reset, possibly 
even a power switch.  I run into a need for that more often than I like.

Thoughts?

-- 

Rick

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Thread

Something like a KVM switch for multiple Raspberry Pis "James Harris" <james.harris.1@gmail.com> - 2015-09-06 18:00 +0100
  Re: Something like a KVM switch for multiple Raspberry Pis Dave Higton <dave@davehigton.me.uk> - 2015-09-06 21:46 +0100
    Re: Something like a KVM switch for multiple Raspberry Pis "James Harris" <james.harris.1@gmail.com> - 2015-09-07 17:42 +0100
  Re: Something like a KVM switch for multiple Raspberry Pis ray carter <ray@zianet.com> - 2015-09-07 00:36 +0000
  Re: Something like a KVM switch for multiple Raspberry Pis davehigton14@gmail.com - 2015-09-07 03:54 -0700
  Re: Something like a KVM switch for multiple Raspberry Pis Gordon Levi <gordon@address.invalid> - 2015-09-08 00:54 +1000
  Re: Something like a KVM switch for multiple Raspberry Pis Andrew Smallshaw <andrews@sdf.lonestar.org> - 2015-09-13 12:45 +0000
    Re: Something like a KVM switch for multiple Raspberry Pis Alan Adams <alan@adamshome.org.uk> - 2015-09-13 19:22 +0100
    Re: Something like a KVM switch for multiple Raspberry Pis Jonathan Lane <tidux@faeroes.freeshell.org> - 2015-09-27 15:28 +0000
  Re: Something like a KVM switch for multiple Raspberry Pis Martin Gregorie <martin@address-in-sig.invalid> - 2015-09-13 13:48 +0000
    Re: Something like a KVM switch for multiple Raspberry Pis David James <david@tcs01.demon.co.uk> - 2015-09-13 14:22 +0000
      Re: Something like a KVM switch for multiple Raspberry Pis Martin Gregorie <martin@address-in-sig.invalid> - 2015-09-13 17:42 +0000
        Re: Something like a KVM switch for multiple Raspberry Pis David James <david@tcs01.demon.co.uk> - 2015-09-16 00:01 +0000
  Re: Something like a KVM switch for multiple Raspberry Pis DisneyWizard the Fantasmic! <wiz@FANTASMIC!disneywizard.com> - 2015-09-17 08:38 -0700
    Re: Something like a KVM switch for multiple Raspberry Pis rickman <gnuarm@gmail.com> - 2015-09-18 08:40 -0400
      Re: Something like a KVM switch for multiple Raspberry Pis Rob Morley <nospam@ntlworld.com> - 2015-09-18 14:26 +0100
      Re: Something like a KVM switch for multiple Raspberry Pis Martin Gregorie <martin@address-in-sig.invalid> - 2015-09-18 18:42 +0000
        Re: Something like a KVM switch for multiple Raspberry Pis rickman <gnuarm@gmail.com> - 2015-09-18 15:09 -0400
          Re: Something like a KVM switch for multiple Raspberry Pis "James Harris" <james.harris.1@gmail.com> - 2015-09-18 20:17 +0100
            Re: Something like a KVM switch for multiple Raspberry Pis Rob <nomail@example.com> - 2015-09-18 21:35 +0000
              Re: Something like a KVM switch for multiple Raspberry Pis "James Harris" <james.harris.1@gmail.com> - 2015-09-18 23:19 +0100
                Re: Something like a KVM switch for multiple Raspberry Pis Rob <nomail@example.com> - 2015-09-19 06:48 +0000
                Re: Something like a KVM switch for multiple Raspberry Pis "James Harris" <james.harris.1@gmail.com> - 2015-09-19 11:15 +0100
                Re: Something like a KVM switch for multiple Raspberry Pis mm0fmf <none@mailinator.com> - 2015-09-19 08:13 +0100
                Re: Something like a KVM switch for multiple Raspberry Pis "James Harris" <james.harris.1@gmail.com> - 2015-09-19 11:19 +0100
            Re: Something like a KVM switch for multiple Raspberry Pis rickman <gnuarm@gmail.com> - 2015-09-19 11:31 -0400
            Re: Something like a KVM switch for multiple Raspberry Pis druck <news@druck.org.uk> - 2015-09-19 19:39 +0100
              Re: Something like a KVM switch for multiple Raspberry Pis colonel_hack@yahoo.com - 2015-09-20 22:06 -0700

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