forumisto
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RPi doesn't start with external HDD

Mon Mar 11, 2013 8:33 pm

I have a hard drive 2.5" connected to a USB port on the RPI. The hard drive is powered by a separate power source (cable is manipulated).

When I start the RPI with the hard drive connected, the operating system does not start and the LED does not blink. If I disconnect the hard drive, the RPI boot succesfully.
If connect the hard drive while operating system is booting, there aren't problems.

What could it be? How do you solve that problem?

Thank you.

(Excuse my bad English)

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mahjongg
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Re: RPi doesn't start with external HDD

Mon Mar 11, 2013 8:56 pm

the PI cannot power your external hard disk!

It has a fuse that will limit the voltage reaching the PI when you draw too much current through it.
Solution, use a hard disk that has its own power input and PSU, or power it from a hub.

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Re: RPi doesn't start with external HDD

Mon Mar 11, 2013 9:25 pm

If it works OK plugging it in later, and you have external power, then that should rule out power problems. You could check the volts on the Raspberry during boot just to check there is no dip below say 4.9v, just to be sure.

After that it sounds like a problem with the low level boot loader, which is beyond me. Does the Hard drive have any leds, to indicate what it is doing. Is it accessed during boot attempts.

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Re: RPi doesn't start with external HDD

Mon Mar 11, 2013 11:21 pm

I add: when I reboot the RPi (with sudo reboot command) with the external hard disk connected, it reboots ok, I don't have to disconnect the hard disk.

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 12:02 am

hmm. interesting, when it isn't any power dip that is causing boot problems, the only other speculative idea I have is very far-fetched indeed, and would only really be possible if you happen to be using a model A raspberry PI, and I cannot fathom that this is the case. Also, I never heard of this behavior before, but plenty of people seem to have this working. Still seems to be power related to me.

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 12:24 am

Just guessing like everyone else here, but you mention a "manipulated cable". In which way is the cable manipulated? And which OS do you use?
Does this also happen when you connect a powered USB hub to the Pi and the hard drive to the hub? That assumes that you can at least borrow a hub for testing if you do not have one.
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forumisto
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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 8:23 am

this is the schema :)
Image
http://img209.imageshack.us/img209/2223/rpisch.png

For powering I use a power supply, not usb hub.
The OS is debian wheezy.

poing
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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 8:37 am

The Pi needs more current when booting and the HD needs more current when spinning up. If you reboot the HD is already spinning so then the total system will draw less power. Most likely your PSU is not powerful enough.

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 8:48 am

I suposse 1A as maximum when RPi boots. The power supply gives 3A. Does the hard disk need more than 2A? I think is very much :/

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 8:51 am

poing wrote:The Pi needs more current when booting and the HD needs more current when spinning up. If you reboot the HD is already spinning so then the total system will draw less power. Most likely your PSU is not powerful enough.
Possibly add a switch between the Pi and PSU, so the HD can spin up first? Might help :)
(Although not all USB disks spin up before the USB data link has been established)
forumisto wrote:Does the hard disk need more than 2A
Unlikely, most of the 2.5" disks I have state 1A max current, some as little as 500mA.

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 9:01 am

from that image you are powering the HD from the +5V GPIO pin.
this pin cannot transmit lots of amps,

it will be the HD needing more power to spin up

you may be better off splitting the power off before it comes into the RPi or having a docking gert capacitor from the +5V to the HD
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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 9:40 am

RaTTuS wrote:from that image you are powering the HD from the +5V GPIO pin.
this pin cannot transmit lots of amps,
It looks to me like the 5V is feeding IN to the GPIO pin from the PSU?

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 9:48 am

rpdom wrote:
RaTTuS wrote:from that image you are powering the HD from the +5V GPIO pin.
this pin cannot transmit lots of amps,
It looks to me like the 5V is feeding IN to the GPIO pin from the PSU?
yes you could be right////
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forumisto
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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 10:08 am

the hard disk is like this: http://www.honeybee-online.com/usd/medi ... M9AT00.jpg

as you can see, it need 5V and 1A

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 10:33 am

You are powering the HDD via the RaspPi, and it needs 1A. That is not going to happen; the input fuse on the RaspPi will limit the current and the RaspPi will see a reduced voltage. That is preventing it booting. It is marginal enough that when the RaspPi is not grabbing an inrush current on power-on, the HDD can get what it needs without the voltage dropping too low, but it wont be stable.

You need to either take the power feed from the power input to the Pi, by "manipulating" that lead too, or you need a separate power supply for the HDD (remembering to connect the grounds.)

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 11:26 am

He's NOT powering the HDD from the Pi: the power is going into the GPIO 5v pin, and in parallel to the HDD
Also, because of that, the input poly-fuse isn't in circuit, so that's not the problem.

And he says his power supply is 3A, which should be enough for the Pi (750mA) and the HDD (1A) with another 1A25 spare, so it can't be a power problem

Actually it can

The HDD says 1A, but it could be greater on start-up. And the power supply may be lying when it says 3A

Powering all on at once, the HDD inrush combined with the Pi's boot-up reduces the PSU voltage enough to corrupt the boot.
When the Pi has finished booting, it takes less current, so there's enough left for the HDD to run up when it's inserted.
When the HDD is running, rebooting the Pi succeeds because there's less current used by the HDD so there's enough left for the Pi to read the SD card

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Re: RPi doesn't start with external HDD

Tue Mar 12, 2013 12:46 pm

I would simply install a switch between the GPIO power pin and the power supply. Let the drive spin up then turn on the RPi.
I would also measure the power supply voltage before, during and after booting.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

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Re: RPi doesn't start with external HDD

Fri Mar 15, 2013 12:43 am

Burngate wrote:He's NOT powering the HDD from the Pi: the power is going into the GPIO 5v pin, and in parallel to the HDD
Also, because of that, the input poly-fuse isn't in circuit, so that's not the problem.
Its not a problem, unless you have a short in the PI, or the over-voltage protection diode D17 triggers, then you have a major problem, as your PI will burn out!
Especially because you bypassed the PI's polyfuse (which is an unnecessary operation as well if you directly power the HD).
You should always power the PI through its micro_USB port, as powering through the GPIO bypasses the PI's polyfuse and leaves it unprotected.

You current solution seems to be in two minds how to go about.

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