Powering from USB on Smart TV?


11 posts
by carhandle » Mon May 06, 2013 6:20 am
Have just ordered a Samsung UE46ES8000 which will arrive at the weekend. I’m using my RPi with RaspBMC and am currently powering from a phone charger.

I’m looking into what I can do differently and note that the TV has 3 x USB ports (2 x 5V 0.5A and 1 x 5V 1A).

Will any of these be suitable for powering my RPi? And will it/can it be set up so the RPi is automatically switched on/off as my TV is?

I also believe that it’s possible to control RaspBMC from the TV’s CEC remote over HDMI so I’ll no doubt be back with more questions regarding this.
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by hcuppen » Mon May 06, 2013 8:08 am
great idea, I am also interested! Anyway that you can relay your TV turning on/off to command the pi to do the same will be nice.

Do you turn off your tv often? I mean, if it is on stand-by all the time, the pi will be on all the time too, right?

Remote over hdmi works fine, but you will eventually want something else to type stuff [i use my phone].
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by rpdom » Mon May 06, 2013 8:38 am
carhandle wrote:I’m looking into what I can do differently and note that the TV has 3 x USB ports (2 x 5V 0.5A and 1 x 5V 1A).


The 1A port should be capable of powering your Pi.

And will it/can it be set up so the RPi is automatically switched on/off as my TV is?


I suspect that switching the Pi on will be no problem. Shutting it down, on the other hand, might not be so good.

If the TV just cuts the power to the port when it is switched off, that would be bad. If it somehow manages to tell the Pi to shutdown (through CEC to RaspBMC), that should be ok. If there is a shutdown option on the RaspBMC memu (I've not used RaspBMC, so don't know), you should probably use that and wait for the Pi to shutdown before turning off the TV.
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by carhandle » Mon May 06, 2013 2:11 pm
Thanks for the responses.

I think the optimum solution is to have a button on the remote assigned to powering on/off the Pi. As you say, killing power to the USB is leaving myself open to corruption of Pi’s storage devices.

Actually, on thinking about that, I will probably just keep it running off phone charger – the rest of the family are less inclined to adhere to ‘complicated’ routines WRT turning things off in order. Plus it means i can use the Pi's USB ports for more useful things such as USB Drive and Wireless mini-Keyboard dongle.
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by Paul Webster » Mon May 06, 2013 6:33 pm
I run my XBMC RPi that way (powered from TV USB).
The TV (Sony) is well behaved - it brings the USB power a few seconds after the TV has resumed - and when I use the remote to do a soft power-off at the TV, it sends CEC command to say that the display is going off and I have XBMC set to treat that as a shutdown request. The TV then keeps the uSB power in for a while (maybe 30 seconds) which is plenty of time for RPi to shut itself down.
I also have XBMC set to scan for new files on startup ... which does slow things down a bit at the start but makes it very easy for the family to use.
Not all TVs are as polite.
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by prirpi » Sat Jun 22, 2013 3:30 pm
Hi!
Maybe your experience could guide me over this power(ful) obstacle:
My LED TV usb port acts as a good power supply to my RPI but after using it (switching off, or putting the TV set in sleep mode), if I turn the TV back on, it does turn the RPI on but it is not detected as an active HDMI source... If I disconnect and connect the HDMI connector it does not react, the only solution being to unplug the usb connector and plug it in back to the TV USB port to "see" the RPI... Does anyone have an idea how to go thru this trouble, using the same "unpolite" TV set of course...
Thanks in advance,
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by Apostasy » Thu Jun 27, 2013 1:38 pm
sudo nano /boot/config.txt

Uncomment the line that says "hdmi_force_hotplug=1"
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by Greebe » Wed Jul 03, 2013 2:34 pm
So how do you set up xbmc to shut down with cec? Several people said they got it working but I do not see an option to set Raspbmc to do this. Turning off my JVC does not shutdown the Raspberry PI.

Thanks,
Greebe
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by Mikeb13603 » Mon Aug 19, 2013 7:00 pm
So my dumb question is this:

When you power the RPi from the TV, is this by connecting the TVs USB port (that can supply 1A) to a USB port on the RPi?

Mike
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by drgeoff » Mon Aug 19, 2013 10:58 pm
Mikeb13603 wrote:So my dumb question is this:

When you power the RPi from the TV, is this by connecting the TVs USB port (that can supply 1A) to a USB port on the RPi?

Mike

In theory that could be made to work on all but the first version RPi's which had polyfuses in the 5 volt lines to the USB sockets. In practice you shouldn't be able to buy a cable with the two identical connectors. And you would need to disconnect the other two signal wires in the cable.

What you should do is use a readily available USB to micro-USB cable and connect the TV's USB socket to the micro-USB socket on the RPi. Note that some cables are too long or to thin or use wet string instead of real copper and drop too much voltage resulting in erratic, or even no, operation of the RPi.
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by aussiedean » Thu Sep 19, 2013 4:40 am
Hi all,

First post here so hi to all. My Pi is setup as a media device running latest build of Raspbmc. I have it hooked up to a Samsung TV/Monitor P22770HD ... connected via HDMI and using the remote to control both the TV and the Pi.

The power coming from a USB power supply with at least 1amp supply (5V) .... have tried connecting to the TV USB port ...runs ok but not sure what the amp hour rating is of that port.

My issue is probably similar to what is happening here .... having problems powering up the Pi when I shut down the TV. The settings in the raspbmc cec settings section indicate that the Pi shutdown .... but the problem being when it shuts down the TV the Pi instantly shuts down as well and when turned back on again gives me a warning about incorrect shutdown and dataloss I think it was ... starts normally. Ive changed the setting to suspend and seems to work ok but just not sure I want it running even in standby without the tv on .... I could live with it I suppose but just interested to know if anyone has come accross this before as well.

The other problem being when the Pi shuts down with powering down the TV it doesn't turn back on at all and when the Source button is pushed to HDMI just says no devices found. ... This is the case if its plugged into the TV usb socket (service socket) or powered separately from the wall plug.

Anyway any tips or help would be appreciated.

Dean
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