tstoten
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Joined: Mon Sep 24, 2012 8:41 am

Ethernet is only on when HDMI connected

Mon Sep 24, 2012 9:01 am

I have been attempting to set up my RPi as a web server.
I am using the latest image 2012-09-18-wheezy-raspbian and all goes well. I have the web server set up and working until I unplug or try to start up without HDMI plugged in..
Ethernet simply stops.. Or does not even start.
I want to run headless and have just ethernet and power plugged in but currently I can only run with a monitor plugged in or I get no network.. I want to use the monitor elsewhere..

I have tried various images and cards with the same result.

Is this a known issue or is my RPi stuffed..

If so I might have to splash out and get another one.. I don't think I would need to re-mortgage the house..

MaxK1
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Re: Ethernet is only on when HDMI connected

Mon Sep 24, 2012 6:49 pm

That sounds like a new one! (Sure beats "my keyboard repeats/loses characters"!)

Does it make a difference if you unplug it from the TV end or the Pi end? Does it happen if you
turn the monitor off?
You are in a maze of twisty little passages, all alike.
When General Failure and Major Disaster get together, Private Parts usually suffers.

marcelr
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Joined: Mon Sep 24, 2012 8:07 pm

Re: Ethernet is only on when HDMI connected

Mon Sep 24, 2012 8:13 pm

I ran into the very same problem today. I am using slackwarearm 13.37 on my raspberry pi.
I hooked up the Pi to an old tv-set (composite video), in the boot messages it was complaining about not having enough memory. The problem disappeared when I exchanged the default start.elf with arm240_start.elf. Since I want to run my Pi as a headless server, for me this will be the best option in terms of memory availability anyway.

HTH

marcelr

obcd
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Re: Ethernet is only on when HDMI connected

Mon Sep 24, 2012 8:57 pm

Indeed the memory settings could be an issue. It's possible that the Pi is using a different video resolution with and without monitor connected. Depending upon that, more or less video memory might be needed.
Another thing possible is that the Pi finds a ground connection trough the hdmi cable and the monitor. So maybe a ground wire between the Pi gnd and the mains earth also will make it work.
I seem to remember already a case where it was like that. You can for instance use the outer of the composite video plug as Pi gnd.
If that fixes the problem, another power supply will likely do so as well. (A piece of wire is cheaper.)

MaxK1
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Re: Ethernet is only on when HDMI connected

Tue Sep 25, 2012 12:05 am

I was thinking a mechanical problem, but obcd's reply may be quite valid.
You are in a maze of twisty little passages, all alike.
When General Failure and Major Disaster get together, Private Parts usually suffers.

MaxK1
Posts: 1043
Joined: Sun Aug 26, 2012 11:34 pm

Re: Ethernet is only on when HDMI connected

Tue Sep 25, 2012 12:54 am

Re-reading.... This sounds like 2 unrelated issues. The op indicated an ethernet problem without an HDMI monitor connected. The Slackware issue may well just be a memory split problem. I haven't run Slackware on the Pi (first time I've had any machine NOT running Slackware!) so I can't comment on the issue, but I will ask if you have either a swap partition or swap file.

To the OP: what error messages do you see on a composite monitor. (If you can connect one) Alternatively, what shows up in 'dmesg' if you unplug the monitor, wait for the net connection to go elsewhere, and then plug the monitor back in?
You are in a maze of twisty little passages, all alike.
When General Failure and Major Disaster get together, Private Parts usually suffers.

tstoten
Posts: 3
Joined: Mon Sep 24, 2012 8:41 am

Re: Ethernet is only on when HDMI connected

Wed Sep 26, 2012 6:33 am

Okay...
sorry it took a while to get back.
After looking at dmesg, as MaxK1 suggested it appeared that when I unplugged HDMI ALL USB devices failed not just ethernet.
I don't know if I was getting some power from HDMI or something but I guesed that it was just another power issue so I went and bought a better power supply and cable..
Turns out it wasn't the power supply but the cable. Everything is fine with the old power supply and the new cable..
Thing is,the old cable is thicker and shorter than the new..

Ow well.. All is well.. :)
Thanks

obcd
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Joined: Sun Jul 29, 2012 9:06 pm

Re: Ethernet is only on when HDMI connected

Wed Sep 26, 2012 7:38 am

The important thing is that it works, but one thing is confusing.

It worked before if you connected the screen with the (bad) cable. It didn't without the screen connected.
You replaced the hdmi cable, and now it works? You wanted it headless, so what's the purpose of the cable?

tstoten
Posts: 3
Joined: Mon Sep 24, 2012 8:41 am

Re: Ethernet is only on when HDMI connected

Wed Sep 26, 2012 7:42 am

obcd wrote:It worked before if you connected the screen with the (bad) cable. It didn't without the screen connected.
You replaced the hdmi cable, and now it works? You wanted it headless, so what's the purpose of the cable?
I replaced the power cable not the HDMI cable.

It never worked without the HDMI connected but now (with the new power cable) it works without HDMI..

obcd
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Re: Ethernet is only on when HDMI connected

Wed Sep 26, 2012 7:54 am

That clears it up. thanks.

Zej
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Re: Ethernet is only on when HDMI connected

Thu Oct 04, 2012 10:34 am

Had a similar problem trying running the Pi headless (ie no display attached)
If the composite video cable was disconnected, the network LED's turn off and ethernet adapter stopped working.

Fixed by connecting ground to the outer shield on video or USB connector.
(take care if you do this or use one of those yellow Earth bonding plugs)
I think my problem was caused by floating voltages from switched-mode power supplies and lack of a ground on the USB power cable.

simonrdavies
Posts: 1
Joined: Fri Oct 12, 2012 9:51 pm

Re: Ethernet is only on when HDMI connected

Fri Oct 12, 2012 10:01 pm

I had exactly the same prblem, which was resolved by using a power supply with a higher amper output.. However it seems to me it is more to do with the power consumption of the power supply unit and not to do with the problem of grounding.

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mahjongg
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Re: Ethernet is only on when HDMI connected

Fri Oct 12, 2012 11:15 pm

Many of the bad (fake) PSU's (as seen on the frontpage recently) emit a lot of HF noise onto the mains, but also onto the 5V output, relative to earth (ground) this can disrupt ethernet communications, if the HF noise isn't shorted to a reliable ground. Plugging in the HDMI can do that as the TV is grounded, and so connecting the HDMI cable also grounds the PI (more or less).

drgeoff
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Re: Ethernet is only on when HDMI connected

Sat Oct 13, 2012 8:50 am

Perhaps the connection of the HDMI or composite cable provides a parallel path to the negative PSU wire, thereby lowering the resistance and increasing the voltage at the RPi slightly. Though for that to happen the negative of the PSU would need to be earthed which is not the case with many of them, certainly not if the PSU has a 2-pin mains plug.

rpifreeze
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Re: Ethernet is only on when HDMI connected

Sun Oct 14, 2012 5:37 pm

mahjongg wrote:Many of the bad (fake) PSU's (as seen on the frontpage recently) emit a lot of HF noise onto the mains, but also onto the 5V output,
...and how would you comment USB hubs and powering Pi from usb hub ? IMHO (not electric expert), using hubs would not cause such errors on PI, but it does....so it's not an issue as you described and shouldn't affect Pi stability.
usb and broadcom issues will never be solved...Too much time passed, too much to be done...

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mahjongg
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Re: Ethernet is only on when HDMI connected

Sun Oct 14, 2012 7:28 pm

rpifreeze wrote:
mahjongg wrote:Many of the bad (fake) PSU's (as seen on the frontpage recently) emit a lot of HF noise onto the mains, but also onto the 5V output,
...and how would you comment USB hubs and powering Pi from usb hub ? IMHO (not electric expert), using hubs would not cause such errors on PI, but it does....so it's not an issue as you described and shouldn't affect Pi stability.
It depends on many factors, but even a hub would get electrical interference signals from the PSU, as it is present on the GND line of the system, (relative to earth) not just on the 5V line.

rpifreeze
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Re: Ethernet is only on when HDMI connected

Sun Oct 14, 2012 9:24 pm

>It depends on many factors
Ok, so the whole world, tens of thousands of users are left with something that is working only with specific PSU...?
99% are using bad psu-s ?
C'mon guys, half of posts on forum are related to freezing, booting issue, vanishing network cards, reboots, locks and so on.
For me - this hardware is a failure. We all know it, but nobody is willing to tell this loudly. Anyone to comment please ?
What do I do wrong ?
Or better, what should I do to have a stable Pi ?
I'm waiting for it for the last few months, spending many hours on reading forums, trying fixes etc etc.
I have two Pi units (different rev, according to /proc/cpuinfo)
I've tried:
- SEVEN PSU-s
- TWO battery banks (Polymer Li-Ion) ranging from 2 to 4 Amps, each time with different cables, and everyone's saying to me that I have bad PSU. Big lie!
I also tried tens of SD cards, from 2 to 10 class speed, different sizes (2-32 GB)
I tried different WLAN and LAN USB adapters - they all behave the same, no matter if connected to HUB, through Yeti cable (2x0,5A), no matter what I do, for the last few months, this hardware is instable and useless because I cannot download DVD file from the internet with a speed of 300 kB/s.
Period.
For interested in RPi - wait few months, then buy revision 20 of it, once chipset or chipset vendor is replaced and electronics on board is fixed.
usb and broadcom issues will never be solved...Too much time passed, too much to be done...

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mahjongg
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Re: Ethernet is only on when HDMI connected

Mon Oct 15, 2012 7:49 pm

Rant over yet?

Do you want help from me or should I just ignore your questions? :x

I'm really sorry you have ethernet problems, but reading the forum each day, and having done over 1700 posts, I think I can say with some confidence that most people do not have the kind of ethernet problems you describe. Just one other case in the last few months, and in that case the ultimate cause did appear to be switching noise from a probably really bad PSU that disturbed a ADSL connection. In the mean time there are about half a million units in the field!

But If you think your hardware is broken, then return it under guarantee!

Noise on the power supply is currently just a theory of me, because of that one single case similar to yours, its in no way a well known fact, i'm just grasping for straws to find out why you have this problem.

rpifreeze
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Re: Ethernet is only on when HDMI connected

Tue Oct 16, 2012 7:46 pm

mahjong
Nobody cares about PSU, or defining "what means good psu". Foundation washes hands away too, saying "buy better one". They should make some official statement, suggestion on such units, but if that doesn't happen, then we all drop all problems to HW. This si correct way of thinking and maybe there is some truth in it, that Pi doesn't have some....dont know, fuses, stabilizers ? However, nothing such happens. I've been to one shop today and saw 220/230 v PSU with micro usb end. I've counted at least 6 of different vendors, but am I supposed to test all of them ? Why Foundation hasn't got a voice in this matter, or gave details of needed PSU ?
Am I going to buy a seventh PSU ? But which one....? Tries 1A, 2A, 2,5A, still problems
Having Pi right now is like having a car for which, gasoline isn't sold and people try all available substances to fuel it. Doesn't make sense.

You're saying about other interferences. This is NOT my problem. IMO, I have a buggy hardware and yes, I'm going to return it, but what reason should I give for this return ? This all makes no sense. HW is buggy by design and period.
EOT
usb and broadcom issues will never be solved...Too much time passed, too much to be done...

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