Frosty66
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Not booting up

Tue May 20, 2014 8:59 am

I had a problem that my Pi would not boot up, I just had a blank screen.

I have a WiFi USB dongle and a wireless keybord USB dongle and if after turning on the Pi I take one of the dongles out and put it back again, or simply put one in if it were not already in, the Pi springs to life.

It's good that I can get it going just by doing this but it's a nusance, can anyone suggest a solution to this ?

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FTrevorGowen
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Re: Not booting up

Tue May 20, 2014 12:15 pm

Frosty66 wrote:I had a problem that my Pi would not boot up, I just had a blank screen.
I have a WiFi USB dongle and a wireless keybord USB dongle and if after turning on the Pi I take one of the dongles out and put it back again, or simply put one in if it were not already in, the Pi springs to life.
It's good that I can get it going just by doing this but it's a nusance, can anyone suggest a solution to this ?
This is probably a "power issue". Most WiFi dongles require up to 500mA peak current and are intended to be use in a "high power" usb port** (like those on a laptop, notebook, powered hub etc.) where as the Pi's ports can only supply ~140mA each when used with a good PSU and USB cable that ensures that there is at least 4.75V at the Pi testpoints (TP1 & TP2). So:
1) Check your testpoint voltage.
2) If <4.75V move the WiFi dongle to a powered hub or try using a wired keyboard since such require less current than wireless ones.
Finally, since the Pi has a fairly small "reservoir" capacitor, the USB ports should not be treated as "hot-pluggable". (Sometimes the extra capacitance provided by an external, unpowered, hub improves "hot-pluggability")
Trev.
** All USB ports should support "low-power" (<=100 mA) devices. Besides the "standard high-power" ports that should provide up to 500mA there are now, so-called "charging ports" which may supply 1A (so long as the hub's PSU is capable of such), these should be labelled such or be of a "different colour".
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

Frosty66
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Re: Not booting up

Tue May 20, 2014 8:13 pm

Oh I see yes I never thought of anything like that. The kit I have came with a powered 4x USB port, now I know why !!! :-)

Thanks so much for the help.

Frosty66
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Re: Not booting up

Wed May 21, 2014 4:17 pm

However, is this is to do with power, it should book OK when neither dongle is is yes ? It doesn't, if I try to boot up with no dongles it doesnt boot, when I put a dongle in it does.....

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williamhbell
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Re: Not booting up

Wed May 21, 2014 8:10 pm

Frosty66 wrote:However, is this is to do with power, it should book OK when neither dongle is is yes ? It doesn't, if I try to boot up with no dongles it doesnt boot, when I put a dongle in it does.....
Can you define "doesn't"? When there is no keyboard or mouse present, then the Raspberry Pi will switch to headless mode and not output the video signal. You should see the lights on the board flash though and be able to connect to it using ssh. You need a minimum of the keyboard to be present for video to be shown.

Frosty66
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Re: Not booting up

Wed May 21, 2014 8:19 pm

Ah OK so hopefullly that might still solve my problem them, just need to find that powered USB that came with it ! :-)

Frosty66
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Re: Not booting up

Wed May 21, 2014 8:32 pm

Right I have the powered USB. However surprisingly I still have the same problem. I have the red power light on and oasionally the green ACT one flashes but nothing on screen.

When I power up the Pi the screen is blank, only when I plug either the WiFi or wireless keyboard dongle directly into the Pi (either by taking one out and replacing it or not having them in the first place) do I get the colour splash on the screen and then the screen full of text as it starts to boot.

Inserting the powered USB into the Pi whilst the dongles are plugged into the powered USB does not ause it to boot. Only when I plug a dongle directly into the Pi does it then boot

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Re: Not booting up

Wed May 21, 2014 10:22 pm

Frosty66 wrote:Right I have the powered USB. However surprisingly I still have the same problem. I have the red power light on and oasionally the green ACT one flashes but nothing on screen.
When I power up the Pi the screen is blank, only when I plug either the WiFi or wireless keyboard dongle directly into the Pi (either by taking one out and replacing it or not having them in the first place) do I get the colour splash on the screen and then the screen full of text as it starts to boot.
Inserting the powered USB into the Pi whilst the dongles are plugged into the powered USB does not ause it to boot. Only when I plug a dongle directly into the Pi does it then boot
Just to clarify things further:
Is your Pi a model A (with one USB port and no ethernet port) or a model B (with two USB ports and an ethernet port)?
If the latter, is it a 'B1' (256Mb & USB polyfuses) or (more likely) a 'B2' (512Mb w/o USB polyfuses).
How do you power your Pi and the powered hub?
For example:
1) The hub has a (better than) 5V 2A PSU and the Pi is powered via a "charging" USB port on the hub**
2) A (better than) 5V 2A PSU with multiple outputs (or an "inverted" 'Y' cable to split the power) to power both the hub and the Pi.****
3) The hub and Pi each have their own, separate, PSU (Not recommended)
Finally do you know if your hub "backpowers" (this "out-of-spec feature" of cheaper hubs can allow a single PSU to be used but, because the Pi's overvoltage and short-circuit protection {polyfuse + "crow-bar" circuit} is by-passed introduces some risk)
Trev.
** See my previous post
**** My preferred method, predominantly with my model 'A' Pi, when I need network connectivity using a USB-to-LAN adapter (rather than a WiFi dongle) when GPIO-connected circuits are "under-test".
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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williamhbell
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Re: Not booting up

Wed May 21, 2014 11:52 pm

Frosty66 wrote:Right I have the powered USB. However surprisingly I still have the same problem. I have the red power light on and oasionally the green ACT one flashes but nothing on screen.
This probably means that the keyboard is not recognised due to a power problem or there is some USB issue with the hub and the keyboard.

When you power up the Raspberry Pi and the powered hub, do you power the Raspberry Pi and the powered hub at the same time? Some powered hubs provide power backwards and some do not. For some powered hubs, the Raspberry Pi will start to boot without the micro usb power being on. then you can hit power problems too. To be completely safe, can you try to power the micro usb to the Raspberry Pi and the powered hub at exactly the same time?
Frosty66 wrote:When I power up the Pi the screen is blank, only when I plug either the WiFi or wireless keyboard dongle directly into the Pi (either by taking one out and replacing it or not having them in the first place) do I get the colour splash on the screen and then the screen full of text as it starts to boot.
This sounds like the USB communication is not getting through to the Raspberry Pi. I can create a similar problem with a low spec. powered hub and a wifi dongle. The problem can be that the wifi dongle is drawing enough current that a low spec. powered hub does not allow the Raspberry Pi to communicate with the keyboard. Can you provide the current per port specifications for your powered hub, as well as the model information? (As the moderator suggests, USB powering problems are more complicated with the version 1 Model B Raspberry Pis.)
Frosty66 wrote:Inserting the powered USB into the Pi whilst the dongles are plugged into the powered USB does not cause it to boot. Only when I plug a dongle directly into the Pi does it then boot
It sounds like the hub also has power limitations. Can you specify your WiFi dongle model too? It tends to be necessary to find a slightly higher specification powered hub with a higher USB current limit.

Frosty66
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Re: Not booting up

Thu May 22, 2014 10:43 am

I have just tried a standard wired USB keyboard with no dongles inserted but directly into the Pi and also the powered USB. The Pi doesn't boot at all, like this including taking it out and back in after powering up the Pi.

It is a Model B Pi, two on board USB plus an ethernet, I'm not sure how to identify it further, it's from a pakaged kit from Maplin.co.uk including the powered USB. The powered USB is not branded but is described as a 4 Port 2.0 triangular Desktop Hub and is model "USK".

http://www.maplin.co.uk/p/raspberry-pi- ... oard-n34qg

Unfortunately I don't have another powered USB to try on it so it it is due to that I will have to order one, any suggestions which one is definately OK ?

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Re: Not booting up

Thu May 22, 2014 10:47 am

Time to go back to Maplin's with a broken RPi.
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Frosty66
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Re: Not booting up

Thu May 22, 2014 10:49 am

According to the Maplin site this kit has a model B Pi with 512MB memory which from what has been said so far makes it a B2 ?

Frosty66
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Re: Not booting up

Thu May 22, 2014 1:34 pm

I have been using Raspbian so far, I just tried Arch Linux and it does not suffer this problem at all, it will boot regardless of the presence or insertion of any dongle. Is there perhaps some config needed in Raspbian that would help ?

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Re: Not booting up

Sat May 24, 2014 12:30 am

Frosty66 wrote:I have just tried a standard wired USB keyboard with no dongles inserted but directly into the Pi and also the powered USB. The Pi doesn't boot at all, like this including taking it out and back in after powering up the Pi.
If you remove the powered hub from the Raspberry Pi USB and connect just the keyboard to the Raspberry Pi, does it boot?

As the moderator said, using a powered hub as well as a power supply to the Raspberry Pi is not ideal. It can just about work, but the powered hub must be powered at the same time as the Raspberry Pi power supply. Can you first test if the Raspberry Pi will boot without the powered hub?

What type of USB wifi dongle is it?

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