Re: Ejecting/Powering off/ -> Turn off the device lamp.

Andy Kennedy
2006-05-22T16:50:10Z

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Alan Stern wrote:
> On Mon, 22 May 2006, Andy Kennedy wrote:
>
>
>> All,
>>
>> I have done an extensive search on this issue and cannot find the answer
>> to my specific question. Whereas I understand that an individual device
>> on a USB host (on board) cannot be "powered off" nor "ejected" I wonder
>> if the device can be sent a command from userspace to turn off it's LED
>> indicator lamp. Most of the devices that I have seen, when the device
>> is no longer in use, goes into a blink cycle.
>>
>> Is there a way to signal the device to stop the cycle and actually power
>> off the LED?
>>
>
> It's hard to answer that question without knowing what kind of device
> you're talking about. Some USB devices (like hubs) can be told to turn
> off their indicators; most cannot.
>
> Alan Stern
>
Very sorry. . . I did leave out the most important part: I am working
with various flash disks / USB mass storage devices.

I am working with an embedded system that will have no user interaction
save the USB port. The unit will recognize the mass storage device via
the hotplug scripts, then execute a series of commands. . . after which
the device will be unmounted and then could be removed. That is the
purpose for wanting to extinguish the lamp. It would be hard to explain
to a lay person to "Watch the little light. It should blink very fast
for a few seconds/minutes then blink slow for a few seconds, then fast
again. . . then you can remove it." and expect them to comprehend the
meaning of the "little blinking light."

I have TTLs on the embedded system; I may just have to use those.

Andy Kennedy

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