small portable display for RPi

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Hello to all,

I'm looking for a small portable display which can be used in
combination with almost any RPi (model B/B+/2/3).  
Most important: The display should be powered by its own battery (no
external power source except for charging the battery) and it should be
as small as possible. The resolution  can be quite low as long as a
standard console font can be read, and the display does not need to
have features like a touchscreen or something like that. The battery
does not have to last for a long time either, one hour would be way  
enough. A straight-forward plug'n'play minimal display would be great..

The main purpose will be to plug it in and get the console  
displayed (no graphical interface required, just simple shell
environment), mostly on headless Raspberries for troubleshooting issues.
I don't care about HDMI or the composite-AV-Port as long as the
text output can be read.

Does anyone have some hints for me?

--  
[null]

Re: small portable display for RPi
On 03/02/17 07:40, Stephan Elinghaus wrote:
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find an old netbook or similar and i9nstall a basic linux on it and  
network in to the pi.

Honestly, it will be  cheaper than some kind of tiny hdmi or so on monitor


--  
Canada is all right really, though not for the whole weekend.

"Saki"

Re: small portable display for RPi

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Agreed. The OP is overthinking this. Any decent console app on a smart
device or laptop will serve this purpose.

--  
If you're not part of the solution, you're part of the precipitate.

Re: small portable display for RPi
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I will have to disagree. I have been a few decades in the field
with such systems (OK, they were physically a lot larger 30 years ago).

In around a third of cases you need good, old console access.
The PIs are not the exception here.

For the PI this means a) a serial cable to the serial console
b) a USB keyboard/mouse combo and a portable HDMI screen.
I use the ones from hardkernel.com (click on displays on the left
hand side). I love the old vu8 (discontinued, replaced by vu8c).
I also use the small 3.3V console thingies from this site, but I
have to crimp new molex connectors on them.

I have a small 12V battery with a 12V/5V regulator for power to
the screen. A 6Ah battery lasts nearly two hours.

-- mrr






Re: small portable display for RPi
Am 2017-02-03 hat The Natural Philosopher geschrieben:
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Thanks for your answer, but this won't work for me.
All my Pis are running headless. The main purpose for the display  
is troubleshooting issues. If the pi doesn't even come up
the (not working) network access is quite useless then.
I think the mentioned car monitor will be the best for me.

--  
[signature left intentionally blank]

Re: small portable display for RPi
On 06/02/17 07:27, Stephan Elinghaus wrote:
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Ah. OK.

The same reason we used to have reverse terminal servers on remote  
serves. To watch the bios and boot messages.

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Probably

--  
New Socialism consists essentially in being seen to have your heart in  
the right place whilst your head is in the clouds and your hand is in  
We've slightly trimmed the long signature. Click to see the full one.
Re: small portable display for RPi
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Look for things like Car Reversing monitors. You'll need to hook up a
12v battery but most of them seem take composite video in.

Gordon

Re: small portable display for RPi
On 03/02/17 07:40, Stephan Elinghaus wrote:
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Or without wireless, some PDAs & mobile phones that connect to desktop  
computers over a USB cable are able to use that computer's network  
connection.

https://en.wikipedia.org/wiki/Ethernet_over_USB

Maybe can do same with r-Pi?

The host linux driver is usbnet

http://www.linux-usb.org/usbnet/

(above is theoretical, I haven't it linux)

--  
Adrian C

Re: small portable display for RPi
Am 2017-02-03 hat Stephan Elinghaus geschrieben:
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Thanks for all the answers. I think I'll give the car monitor a try,
seems to be the best solution for my purposes.

--  
[footer space for rent]

Re: small portable display for RPi
On Mon, 6 Feb 2017 08:32:44 +0100, Stephan Elinghaus

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A mate has a small battery powered monitor, bought from eBay that has
all sorts of inputs that I believe was 'designed' for CCTV field use?

I've used it with him both on CCTV (Composite) and a PC (VGA) and it
worked well for both. I *think* it also had an HDMI port.

If it didn't and you can find a battery powered PC (VGA) monitor, I
have used an HDMI to VGA dongle with no issue on my RPi's.

http://www.ugreen.com.cn/product-784-en.html

The only requirement is that it has to be powered on *before* you
power on (or boot possibly) the Pi but I think that's because it
(Linux?) defaults to the CV port otherwise (and may not switch back to
the HDMI dynamically). I think you can set it to the HDMI
(raspi-config?).

I just use a twin output USB PSU, one uUSB lead straight to the dongle
and another uUSB power lead to the Pi has a power switch on it (easier
than trying to plug the uUSB connector in poor lighting or access
conditions).

Cheers, T i m

Re: small portable display for RPi
On 09/02/2017 12:43, T i m wrote:
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Forcing the RPi to use HDMI is done by setting "hdmi_force_hotplug=1" in  
/boot/config.txt and rebooting. Also see other related HDMI-settings:  
http://elinux.org/RPiconfig


Re: small portable display for RPi
On Thu, 9 Feb 2017 13:12:45 +0100, "A. Dumas"

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Ah ok. Checking here it was possibly 'Overscan' I was thinking of
(that presumably also modifies config.txt).

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Cheers.

So, I guess it would make sense to always set the output to HDMI if
you never use the composite video output?

Cheers, T i m



Re: small portable display for RPi
On 11/02/2017 13:34, T i m wrote:
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Yeah maybe, but I never needed to!

Re: small portable display for RPi
On Sat, 11 Feb 2017 14:06:14 +0100, "A. Dumas"

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1) If you boot a Pi / Raspbian headless and then plug in a real HDMI
TV / Monitor, does it always output video to the HDMI port?

2) When I have tried to retrospectively plug in an HDMI > VGA adaptor
I don't think it's detected it and had to reboot to ensure that it
did.

Hence why I was wondering if it might be a 'good idea' to make it a
default (and am not sure why it isn't in the first place. I mean, now
many people use composite video (fir it to be the default)? I know it
might be the lowest common denominator etc but ...

Cheers, T i m

Re: small portable display for RPi

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if you put:
hdmi_force_hotplug=1
in config.txt then yes.

Bye Jack


Re: small portable display for RPi
On Tue, 14 Feb 2017 00:02:33 -0800 (PST), snipped-for-privacy@gmail.com wrote:


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Ok thanks. I'll give that a try (and see if it then handles the
HDMI-VGA converter hotplug).

Cheers, T i m

Re: small portable display for RPi
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I think the issue is that the Pi can detect the presence of an HDMI cable,
but not composite video[1].  Hence:

HDMI cable detected: output on HDMI
else
output on composite video

means in practice you can plug in either before boot and it'll work without
any config.

If you default to HDMI you then have a chicken-and-egg problem because the
composite video user can't see anything to change the setting to that port.
(pulling the SD card and hacking config.txt on another machine isn't very
friendly to the novice user)

It is only in the case of post-boot HDMI connection that the default is
- unhelpful and you can change the hotplug setting for that since you can
boot with HDMI attached and then see to change the setting.

I don't know if the Pi can run both HDMI and composite at the same time, but
if so it would't be very useful - resolution would be limited to 640x480.  
So practically you do have to select one.

Theo

[1] while some boards have it as a TRRS jack that might have a switch to
detect a plug, on others it's just a pin header.

Re: small portable display for RPi
On 14 Feb 2017 13:49:41 +0000 (GMT), Theo

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<sorry I've not been back sooner>
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Ok.

Oh, but not have it switch dynamically to HDMI if inserted after boot,
ok. That isn't so much an issue since I have discovered SSH (late to
the game I know <g>) but it can be a pain of you need to get access to
a machine that isn't on the network for some reason.
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Understood, however, I (personally) don't have a composite video
monitor on hand (I do still have them though) but do have several HDMI
devices around, including the HDMI > VGA adaptor and it would be nice
to know I would get video output on those if required.
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Understood.

Understood.
Cheers, T i m

Re: small portable display for RPi
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I use the serial port for this.
You can get a USB-serial adapter which works with the Pi's 3.3V
serial port directly from Adafruit, and it's very cheap. Use it
with a laptop/netbook/whatever with a serial port. Can probably
even use a smartphone with a terminal app.

--  
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Re: small portable display for RPi
On 11/02/2017 10:45, Andrew Gabriel wrote:
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A laptop/netbook/whatever with a *USB* port: the adapter cable with  
embedded convertor chip is from GPIO pins on the RPi side to USB plug on  
the other. So you also need appropriate drivers for this particular  
serial-USB chip (there are 2 older and 1 current version from Adafruit).  
And beforehand you need to enable the UART serial function of those GPIO  
pins, which on the RPi3 requires you to disable bluetooth, I think.

Or if you *do* want to use a serial port on the second device, I guess  
you need another adapter RS232->USB. I think with phones you may end up  
in adapter hell: microUSB->RS232->USBfemale<->USBmale<-GPIOserial.


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