hvc123
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Re: Power over HDMI

Sun Jan 22, 2012 3:28 pm

Heres one for you guys,

i wonder if it is at all possible to power the RPi from the HDMI? i have read somewhere that HDMI has power going down it upto 2 watts !!!?

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Gert van Loo
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Re: Power over HDMI

Sun Jan 22, 2012 4:09 pm

This has come up again and again. The maximum current an HDMI sink can take is 50mA. An HDMI sink can not supply current.That is from the official HDMI standard.

Just for completeness sake: The Rapsberery-Pi is an HDMI source. A TV is an HDMI sink.

hvc123
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Re: Power over HDMI

Sun Jan 22, 2012 4:11 pm

OK OK just a question…. at least you didnt say use search!

ta

AlanM
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Re: Power over HDMI

Sun Jan 22, 2012 4:14 pm

There is the MHL standard which is intended to supply charging power whilst being a HDMI sink, so a TV would supply power to a device plugged into it.  Although it is associated with HDMI it isn't HDMI.

Phones like the Samsung Galaxy S2 have a MHL port on them.  At the moment if you plug it into most HDMI TVs the phone will still run on battery power, but there are a few TVs out there which have MHL compliant sockets so that the phone can run on external power.  This means playing video from the phone on the TV won't drain the battery completely.

hvc123
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Re: Power over HDMI

Sun Jan 22, 2012 4:23 pm

i gotta say that its a shame its only 50ma not 500ma as 5v @ 500ma = 2.5 watts

ViewTouch
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Re: Power over HDMI

Thu Jan 26, 2012 5:20 pm

By mid year the market is going to be seeing a wave of HDMI plug computers with MHL.  It's my hope that the Raspberry Pi will achieve a form factor of HDMI with MHL, essentially turning any TV or display into a Linux computer or an X terminal merely by being plugged into the HDMI port of any TV or display.  If Raspberry Pi doesn't do this, then I would bet real money that it will happen anyway.  I do, of course, hope that Raspberry Pi is the first HDMI MHL Linux plug computer/terminal.

When this scenario arrives then we will have reached the point in time where a PC is a tiny device you can carry in your pocket and plug into any HDMI display or TV.  FXI tech in Norway is preparing one of these, too, by the way, and I hope it's the first of many.  Linux has been quite shut out of the tablet & smartphone device market, but this is a chance for it to play in the HDMI MHL dongle market and to dominate it.  Much of whether this comes to be is, in my opinion, in the hands of the Raspberry Pi people and their 'customers'.

fordcars
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Re: Power over HDMI

Sat May 09, 2015 2:01 pm

Guys, I have managed to power RPi2 over Hdmi here; completely an accident. I use a powered (by USB) hdmi to VGA converter, but this is still nuts

W. H. Heydt
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Re: Power over HDMI

Sat May 09, 2015 7:13 pm

ViewTouch wrote:Linux has been quite shut out of the tablet & smartphone device market....
And just what do you think the OS under Android is? I'll grant you that it is hidden away pretty well... (Likewise, OS/X is unix in a clever plastic disguise.)

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rpdom
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Re: Power over HDMI

Sat May 09, 2015 7:18 pm

Why are you replying to a three year old post? The poster in question hasn't posted since then.

loadbang
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Re: Power over HDMI

Sat May 14, 2016 5:17 pm

rpdom wrote:Why are you replying to a three year old post? The poster in question hasn't posted since then.
No idea. However I'm here as I've just found the RPi will power my HDMI passthru box which also splits Toslink optical and two line level out just fine.

Didge
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Re: Power over HDMI

Sat May 21, 2016 11:26 pm

Heya guys,

Was just passing and searching online myself for the actual voltage and then the amount of watts I could extract from the HDMI port..

Anyway, today I was shopping in town, whizzed through the cables selections and seen an HDMI to micro USB cable, first though was I can hook this to my TV and my Samsung S5, after that did not work many wonders I myself even thought it would at least save me the hassle of powering my Raspberry Pi 2 B with an external PSU..

So I can first hand tell you, it does not work, sadly..

Bummer eh, would be awesome to do such a thing and save allot of hassle every now and again if you could.
But as I found out myself earlier... it's a definite... No, using the HDMI to micro USB cable I came across :(

Hope this clears matters up regardless of the voltages and wattages or anything else..

It's a sound and solid "No!" From me..

loza14
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Re: Power over HDMI

Mon Aug 21, 2017 9:28 am

guys, you know there are HDMI connectors where you can connect external 5V power.
I wonder if this thing would not fry the HDMI port of Raspberry Pi and/or of my monitor?
Did anyone try this?

jjthacker
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Re: Power over HDMI

Sun Jan 14, 2018 6:28 pm

Yes, I Have done this. I connected my Pi 3 to an HDMI to VGA connector (which needed an external 5v supply), pulled out the power supply to shut down, and the Pi continued running (which did admittedly freak me out a little).

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mahjongg
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Re: Power over HDMI

Sun Jan 14, 2018 6:45 pm

jjthacker wrote:
Sun Jan 14, 2018 6:28 pm
Yes, I Have done this. I connected my Pi 3 to an HDMI to VGA connector (which needed an external 5v supply), pulled out the power supply to shut down, and the Pi continued running (which did admittedly freak me out a little).
Thats strange as new PI's even use a specific IC (the RT9741CGV-ND) to block current going into the PI from the 50mA 5V wire used to power the EEPROM in the HDMI monitor, and to limit current flowing out. Older PI's used a simple (BAT54) Schottky diode, but that sometimes burned out, especially when using a cheap HDMI to VGA adapter that "stole" power from the EEPROM, and used much more than 50mA.
This chip allows a few hundred mA going OUT, but blocks all current flowing IN.

IBM Portable PC
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Re: Power over HDMI

Thu Jan 25, 2018 12:52 am

So what is the definitive answer?

Can a Pi 2 be powered safely from the HDMI port, the answer appears to be yes?

glenenglish
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Re: Power over HDMI

Fri Aug 31, 2018 6:23 am

everyone has been barking up the wrong tree

HDMI lends it self to powering the device common mode, just like PoE

If the data rate isn't too high, say 25fps SD, , then it probably will work with standard PoE transformers for ethernet.

do some reading on how PoE works.
you'll be good up to 50W easily done right

Glen.

Heater
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Re: Power over HDMI

Fri Aug 31, 2018 7:29 am

Do you have an example of a working PoHDMI set up? I suspect not.

jamesh
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Re: Power over HDMI

Fri Aug 31, 2018 8:24 am

glenenglish wrote:
Fri Aug 31, 2018 6:23 am
everyone has been barking up the wrong tree

HDMI lends it self to powering the device common mode, just like PoE

If the data rate isn't too high, say 25fps SD, , then it probably will work with standard PoE transformers for ethernet.

do some reading on how PoE works.
you'll be good up to 50W easily done right

Glen.
Talked to a HW guy who knows HDMI, this is nonsense. Please don't try this at home.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
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hippy
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Re: Power over HDMI

Fri Aug 31, 2018 10:36 am

Power over HDMI is possible but it requires an injector at the TV end and a splitter at the Pi end.

This is how things normally are; the TV does not provide 5V output, it receives 5V from the Pi. 0V signals not shown -

Code: Select all

-----------.                                    .--------
          _|_                                  _|_
 Pi      |   |================================|   |   TV
         |   |================================|   |
  .--.   |   |                                |   |
--|5V|-->|___|------------------------------->|___|--> 5V
  `--'     |   Pin 18                  Pin 18   |
-----------'                                    `--------
It is entirely possible to break the cable with a splitter and injector, and reverse the provision of 5V so it comes from the TV side. This requires a PSU to inject the 5V at the TV end -

Code: Select all

                 Splitter         Injector
-----------.     .-------.        .-------.     .--------
          _|_    |_     _|        |_     _|    _|_
 Pi      |   |===| |===| |========| |===| |===|   |   TV
         |   |===| |===| |========| |===| |===|   |
  .--.   |   |   | |   | |        | |   | |   |   |
--|5V|-->|___|---|_| .-|_|<-------|_|-.-|_|-->|___|--> 5V
  `--'     |         |                |         |
-----------'         |                |  .--.   `--------
               5V <--'                `--|5V|--<
                                         `--'
There are products commercially available which allow this to be done. Those are intended to inject 5V towards the TV when a product with HDMI output does not provide the 5V signalling to the TV which a Pi does but that injector can be moved to the TV side as above. It can be proven to work by supplying 5V from the TV side and lighting a LED+R on the Pi side.

It may be possible to remove the splitter on a Pi Zero if pin 18 connects direct to 5V but we do not have full circuit diagrams so the board would have to be examined to tell. For other Pi's their pin 18 does not directly connect to 5V; a blocking diode or a regulator in later Pi's prevents the Pi being powered from pin 18.

Whether a typical HDMI cable would allow enough current to power the Pi I don't know. But the cable between injector and splitter could be replaced by some other cable which does.

It should also be possible to combine the power source with the data signalling, as is done for PoE, though whether simple PoE transformers would provide for this I don't know.

Added: It seems there are commercial products already available similar to what is described above, though in this case sourcing the supply for the HDMI TV from what would be the Pi side -

http://www.skywalker.com/Products/VANCO ... N1050.aspx
http://www.skywalker.com/Products/VANCO ... N1033.aspx

andreklein
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Re: Power over HDMI

Sun Jan 27, 2019 5:39 pm

i have it working on my pi3, it needs a quick plug and disconnect at micro usb power, but when it starts all power comes from hdmi, it runs perfectly.

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