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connecting R Pi to a usb port on a monitor or projector?

Former Member

We're looking to initially use the Pi as part of our campus emergency notification strategy by having the unit always on and displaying a static message.  We've been able to run the Pi by connecting it to the usb port of several monitors and projectors.  Will regularly powering on and off the monitor/projector will be creating a potential problem for the Pi?

Parents

  • Even though ext4 is a really robust journalled filestore, just turning off a *nix system at the power switch rather than with a proper shutdown is asking for trouble.  When the system is quiescent then most of the time ext4 recovers cleanly on next boot, but one day it won't.  You should really avoid doing so.

     

    If such use is unavoidable, I suggest that you plan for it by appropriate system design.  This is actually a fairly common situation, and various solutions are available and well known.  Typically:

     

    1) Protect your /boot partition by keeping it normally unmounted in /etc/fstab:

    /dev/mmcblk0p1        /boot        vfat        noauto,noatime      0 0

     

    2) Make your root (/) filestore read-only.  See http://wiki.debian.org/ReadonlyRoot

     

    3) Use network storage for everything that must be continually writeable, for example using NFS.

     

     

    Given these 3 changes, turning off the power arbitrarily shouldn't matter as far as software is concerned.

     

    Of course hardware issues are a completely different kettle of fish.  Even in the absence of power spikes or unexpected power sequencing as things are turned on or off, the lifetime of hardware is almost always reduced by daily power cycling, and if it's done after every class then I strongly suspect that your equipment will last a shorter time than it otherwise might.  I think you'll have to consider the pros and cons here carefully.

     

    Morgaine.

Reply

  • Even though ext4 is a really robust journalled filestore, just turning off a *nix system at the power switch rather than with a proper shutdown is asking for trouble.  When the system is quiescent then most of the time ext4 recovers cleanly on next boot, but one day it won't.  You should really avoid doing so.

     

    If such use is unavoidable, I suggest that you plan for it by appropriate system design.  This is actually a fairly common situation, and various solutions are available and well known.  Typically:

     

    1) Protect your /boot partition by keeping it normally unmounted in /etc/fstab:

    /dev/mmcblk0p1        /boot        vfat        noauto,noatime      0 0

     

    2) Make your root (/) filestore read-only.  See http://wiki.debian.org/ReadonlyRoot

     

    3) Use network storage for everything that must be continually writeable, for example using NFS.

     

     

    Given these 3 changes, turning off the power arbitrarily shouldn't matter as far as software is concerned.

     

    Of course hardware issues are a completely different kettle of fish.  Even in the absence of power spikes or unexpected power sequencing as things are turned on or off, the lifetime of hardware is almost always reduced by daily power cycling, and if it's done after every class then I strongly suspect that your equipment will last a shorter time than it otherwise might.  I think you'll have to consider the pros and cons here carefully.

     

    Morgaine.

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