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morphy_richards
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kitting out a classroom

Sat Feb 09, 2013 11:39 am

At 4pm on Friday I had a bit of a Brewsters millions moment. My budget had been underreported and I suddenly discovered an extra £700. Our deadline was 4.30 pm on the same day for this financial year and any money left gets "assimilated"
So what's a panicked budget holder to do in such a situation?
Buy a stack of Raspberry Pis. Added to my current stock I now have enough to permanently fit 30 in a classroom.

Layout.
3 rows of 5 pc computers on left side of room
Ditto on the RHS
Network cabling in walls with points next to each row.
To do .. / to think about / ideas / to buy...

I've got a Linux box / server with 8 gig memory. The Pis will primarily act as X terminals to that but can be swapped with an sd card to "Pi mode" too.

They need to be in robust enclosures and deter teefing and jacking (ie. Theft)
(Edit - didnt mean to submit this yet, having a mare with my phone while typing , sitting on west coast mainline to Manchester.... Continuing ...

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morphy_richards
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Re: kitting out a classroom

Sat Feb 09, 2013 11:48 am

Continued.
I'm considering a few networking options,
2 port hubs at end of cable from wall to share each port between rpi and pc with minimum wire mess or a larger hub or switch for each row to share 1 port on the wall with one pc and 5 rpis
Any other options or suggestions which are cost effective?

Also, USB switches to share mouse and keyboard between pc and rpi. Anyone have experience with these things?

Off hand does anyone know if you can have VGA and DVI connected to a monitor at the same time to let pc and rpi share that too. (cant imagine why not)

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rpdom
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Re: kitting out a classroom

Sat Feb 09, 2013 12:05 pm

morphy_richards wrote:Continued.
Off hand does anyone know if you can have VGA and DVI connected to a monitor at the same time to let pc and rpi share that too. (cant imagine why not)
I expect that would depend on the monitor, but most should be ok.

My old Dell has DVI and VGA and an input select button to switch between the two. I have a PC and Pi connected to this (For various reasons the PC is connected to the DVI and the Pi to VGA via a composite->VGA convertor). I also have an old Philips monitor with the same inputs and select button.

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Re: kitting out a classroom

Tue Feb 12, 2013 2:17 pm

I'm thinking of making a network for this like the one below.
There are 3 rooms, each with 30 computers (and the possibility of a fourth being added at some point) so there could be anywhere between 30 to 90 (or even 120) students logged in at any one time.

The server is a HP Prolient with SCSI hard drive and 8 gig of memory in. I'm not sure what speed the processor runs at but it's an Intel Xeon (apparently)

I intend to mount a second network card in here which will connect to the school internet connection.
The main network card will go to "my network"
One cable will go from server to room 1.
Each room has 8 rows (4 X 4, side by side) of work stations. (There are actually ample School Ethernet connections built into the wall but they are maintained by a potentially litigious Managed Service Provider)
I will use a series of 8 port switches (nice and cheap) alongside each row to provide network connections to the "berry terminals"

It will be a bit like this:
Image

To begin with I will try this in just one room, if successful I will extend to my other rooms. If very successful I will do away with most of the Windows computers and just hold a few back for terminal un-friendly work (like sound and video editing).

Will be for teaching Programming,
"IT" (using open office etc.)
Networking (learn how to wire up your own departmental network)

Criticism and suggestions gratefully received. Especially in terms of the topology (must be cost effective) :)

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morphy_richards
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Re: kitting out a classroom

Tue Feb 12, 2013 3:46 pm

Bl00dy big thick solid Victorian walls everywhere and I cant get into the trunking for the existing networking without ripping things apart.
Help!

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Re: kitting out a classroom

Tue Feb 12, 2013 9:08 pm

One possible solution could be to allow each room to establish its own 100 mbs network including its own Linux application server (which I think could be a recycled desktop pc with extra RAM chucked in)
The server in the office will continue as a samba server, as a general file server for student's home directories. It will also be the internet gateway.

There will be no direct network connection between rooms. The high bandwidth stuff (i think) will mainly be the x graphics between server and terminals. This will all take place within room networks.

The less bandwidth dependant file management and internet connection between rooms and server in office could be enabled over either WiFi or Power Packet ( a new version of powerline networking)..
Hmmm....
:?

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rpdom
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Re: kitting out a classroom

Wed Feb 13, 2013 3:58 am

morphy_richards wrote:One possible solution could be to allow each room to establish its own 100 mbs network including its own Linux application server (which I think could be a recycled desktop pc with extra RAM chucked in)
The server in the office will continue as a samba server, as a general file server for student's home directories. It will also be the internet gateway.

There will be no direct network connection between rooms. The high bandwidth stuff (i think) will mainly be the x graphics between server and terminals. This will all take place within room networks.

The less bandwidth dependant file management and internet connection between rooms and server in office could be enabled over either WiFi or Power Packet ( a new version of powerline networking)..
Hmmm....
:?
That sounds do-able :)

As long as you choose a subnet number that doesn't clash with any your MSP is using. You could choose a subnet based on room number or something, as long as it is in one of the Private address ranges.

100MB sounds good. X can take quite a lot of bandwidth at times.

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Re: kitting out a classroom

Wed Feb 13, 2013 10:53 am

rpdom wrote: As long as you choose a subnet number that doesn't clash with any your MSP is using. You could choose a subnet based on room number or something, as long as it is in one of the Private address ranges.
If the server in my office has two network cards, one to connect to the MSP network for internet and a second interface for my little departmental Computing network, would that be a sub net of the main MSP network or would it be an entirely separate network ?

I had imagined it would be the latter and therefore there wouldn't be any such issue.?

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Re: kitting out a classroom

Wed Feb 13, 2013 11:19 am

It must be separate, but it must be very separate. If, for example, the MSP has your PC on the network 192.168.10.x, it may also have a network down in the language laboratories of 192.168.11.x, and the admin office might be on 192.168.100.x. If you use any of those network addresses for your little network, then your PC will get confused and probably wont be able to talk to the admin office etc. In the worst case nor will anyone else, but you're probably safe from that using Windows.

So you should choose a network address that you are sure that the MSP does not use for any network that you can access. There are three ranges that are allocated for these sorts of private network:
10.x.x.x
192.168.x.x
172.16.x.x to 172.31.x.x
If the MSP uses one of those, then you should choose another.

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Re: kitting out a classroom

Wed Feb 13, 2013 12:42 pm

Thanks for that Rurwin. I don't think we use the 10.x.x.x anywhere else so will go with that.

Some fun and games (and I can pretend I'm doing "work")

Image
Mocking up a network. I'm using an old Linksys ADSL wifi router and 4 port switch at the moment as it's what I've got to hand. I'm only interested in the switch part of it. Haven't done anything to setup the (new (but "second hand")) second network card yet other than plug it in.

Turned everything on, just to see what might happen.

Getting some interesting output on the berryterminal

Image
Link up, link down, link up link down (kevent 4 may have been dropped?)
Image
link up, link down, link up, link down, but reported differently.
Image
Lease granted?

I now need to find more out about what I am trying to do.

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Re: kitting out a classroom

Wed Feb 13, 2013 1:55 pm

Second network card was causing a PCI bus error on the server ... un plugged and replugged it, now it works. Now obtains a lease but then stops. More to do but out of time on this for today.
Image

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Re: kitting out a classroom

Wed Feb 13, 2013 4:01 pm

Hello from Berryterminal.

Still have not configured anyting manually.

Logged into server as root. Ran netstat
Got ipaddress for eth1 (second network card)

Added this to config.txt on berryterminal config file
server=192.168.x.xxx
Image
Hewwo!

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Re: kitting out a classroom

Tue Mar 05, 2013 3:21 pm

Starting to get complicated ...
Image
VLE is now running edubuntu. I'm trying to set this up as a single sign on server and unified file manager. Also to be connected to from around the school on random windows computers using Xming.

"Fred" is an example of a LTSP server. Each classroom will have it's own LTSP server. Each teacher will administer their own LTSP server, install software as they wish etc.

Berryterminals and other machines will connect to that classrooms LTSP server (eg. "Fred")

"Fred" will then look to "VLE" for login authorisation and user home directorys.

Setting up LDAP is tricky :?

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Re: kitting out a classroom

Thu Mar 07, 2013 8:34 pm

Decided to go for broke and stick with what I know works for the time being.
My main server, "VLE" works as an LTSP server. It has two NW interfaces and allows the internet connection attached to "eth0" from the school network to be used by my "computing" network on "eth1".
In due course I want this server to be a "Single Sign On" server, internet gateway and file server which will kind of be like a backbone to smaller networks in each ICT room. For now, I'm just setting up a smaller network in my own classroom. Some of my year 10's built one of these smaller servers (this one will be called "Lovelace") today using parts bought from MISCO. Total cost for a quad core server from parts but using ATA hard drive about £120.
Image
In the distance, against the far wall you can see "VLE".

VLE is plugged in to the school network using a patch cable made by one of my year 10's. The first patch cable took us about 40 minutes to make, used up about 6 RJ45 plugs and the cable shrank from 3 meters to 2 meters. After the first one we found we could make them much more quickly.
VLE is also plugged in to quite a big switch with lots of ports. I inherited this switch from a quango organisation that was attached to my school and which became extinct recently. I'm hoping it's just an ordinary dumb unmanaged switch and hasn't got any funny jiggerypokery.

From the big switch with lots of ports I am running a cat 6 cable up into the ceiling and along, then down to each row. So, a 9 spoked(?) star topology.
At the end of each row, on the end of each spoke of the main star, there will be am 8 port switch. 1 port will connect the smaller switch to the big switch with lots of ports. 4 more ports will connect to Berry (thin) terminals and will leave 3 ports free for lessons and experiments with all sorts of crazy network fun.
Here is a closer view
Image

Ran out of time with the small year 10 class but was going to get my big year 10 class to build SD cards for the berryterminals this afternoon.

I tried to do a demo of this process using a r-pi bought from RS recently. It seemed to be a dud, LED lit up but noew video output.
Tried with another r-pi, also a dud?
By then the moment was kind of lost so we packed up the r-pis and got on with doing coursework. After the lesson I tested the same r-pis using an SD card, PSU and DVI cable known to work. Definitely dud. Odd that two were dud in a row.

Over the next week in spare moments myself and when I can get suitable students who can be spared from normal classswork I will finish off adding RJ45 plugs to the rest of the cat 6 cables, add cables to the other side of the classroom and test each r-pi to see how many need to be sent back :twisted:
Going to need lots of trunking soon.

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Re: kitting out a classroom

Thu Mar 07, 2013 9:00 pm

Thanks for the progress report.

It sounds like you are really getting there :)

A pity about the two duff Raspis though. Have you checked the SD card connector pins? Some people have reported that one of the pins sometimes isn't bent up far enough to make contact properly.

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Re: kitting out a classroom

Fri Mar 08, 2013 3:47 pm

Every single one of these 21 Raspberry Pi's is tested and is a dud!
Image
Put in a SD card known to be good with Hard float Wheezy on, I get the ACT light flash for less than a second and then nothing whatsoever... :evil:

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Re: kitting out a classroom

Fri Mar 08, 2013 4:17 pm

How old is the Raspbian image the "known good" card was created from?

Some of the older firmware (from the 256MB model B days) isn't compatible with the newer 512MB versions.

It might be worth downloading a fresh image and trying that.

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Re: kitting out a classroom

Fri Mar 08, 2013 4:22 pm

... quick update.
Phoned RS customer services with the order number and they are shipping out 21 replacements and one free one for the inconvenience on Monday.

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Re: kitting out a classroom

Fri Mar 08, 2013 4:26 pm

rpdom wrote:How old is the Raspbian image the "known good" card was created from?

Some of the older firmware (from the 256MB model B days) isn't compatible with the newer 512MB versions.

It might be worth downloading a fresh image and trying that.
It is older but still post 256MB. I've tested a whole bunch of SD cards with various operating systems and I've been cross checking on an older rev2 512 mb r-pi from an earlier order. The Wheezy sd card is useful for testing because it makes the ACT light flicker for about a minute. Berry-terminal only takes a second or two to boot up and then the light goes dead which makes it harder to judge if its an issue with the video output or just a general issue.
Main thing is I'm getting replacements fairly quickly. :)

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Re: kitting out a classroom

Tue Mar 19, 2013 4:03 pm

This will work well on a small scale - ie. in one classroom

Have got a few quandaries regarding building a network across the whole department.

So the network (computing.lan) will eventually be something like this....

Code: Select all

(internet from school network)---[router]------[switch]----[VLE]
                                                |
                                                +---[LTSP server 1]---[switch] ---{berry terminals}
                                                +---[LTSP server n]
I was originally planning to have VLE do lots of jobs;
A Kerberus and LDAP (file) server
A moodle server to the "normal" school network (shared back to the school network via the router)
A DNS server
A mailserver

The router is an old desktop PC with a few extra NICs chucked in. I've installed ClearOS on it.

Having being reading a fair bit of the Linux Network Administrator's Guide I've gone from a sort decent understanding of what can be done and vaguely aware fuzzy understanding of how it's done to a fuzzy level of vague awareness ....

I have got a few more obsolete desktops knocking around that can be pressed into service if needs be.
How many of the above jobs should be split out to other machines. It seems as though it might be preferable to have DNS server and mailserver at least as separates (or is there not really any issue with combining roles - going and setting up various config files though I seem to be making quite a lot of references to ip addresses from a machine back to itself, which doesn't sound right....

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Re: kitting out a classroom

Wed Mar 20, 2013 5:12 am

Phoned RS customer services with the order number and they are shipping out 21 replacements
and

http://www.raspberrypi.org/archives/3534
Just yesterday I received a batch of 21 units from a school
Coincidence?

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Re: kitting out a classroom

Wed Mar 20, 2013 9:31 am

I was just going to post that also ....
as always it's worth trying the latest version before consigning them to the RMA situation
How To ask Questions :- http://www.catb.org/esr/faqs/smart-questions.html
WARNING - some parts of this post may be erroneous YMMV

1QC43qbL5FySu2Pi51vGqKqxy3UiJgukSX
Covfefe

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Re: kitting out a classroom

Thu Mar 21, 2013 6:54 am

and the retailer who issues RMA number (if they do such a thing) should provide FAQ as a precursor to try to help avoid the need to ship the stuff back.

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Re: kitting out a classroom

Thu Mar 21, 2013 12:51 pm

http://www.raspberrypi.org/archives/3534
Just yesterday I received a batch of 21 units from a school

Coincidence?
Infamy!

Moving on ....


The new batch arrived. (also Hynix)

I took the same high performing students from their GCSE ICT class as the other week. Showed them the post about the memory issue on the Raspi front page and all the comments about our 21 pis and we had a bit of a chuckle that we have managed to caused such a stir.

Anyway, we are pleased that Berryboot and Berryterminal has been updated to work with these newer models as well so we have built some thin clients!

We currently have the setup as shown below

Code: Select all


["Lovelace" LTSP server]----[switchA]-...--[switch1]+-----[berryterminal 1]
                                                    +-----[berryterminal 2]
                                                    +-----[berryterminal 3]
                                                    +-----[berryterminal 4]

                                        

Lovelace has one test student user account and one sudo account at present.
One Berryterminal can log in and display the Edubuntu "unity" desktop.
Plug in a second berryterminal to switch1 and it will boot, send the "discover" process, start x, and then will just go to a black screen. (Have also tried re-powering the switch)
Whichever one works seems to be dependent on which one was turned on first, but the second will not display the LTSP login screen, just a black screen. Only one berryterminal seems able to work on this network at any one time. :?
Can anyone point to anything blindingly obvious that we might not have done / might have done wrong?

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Re: kitting out a classroom

Fri Mar 22, 2013 9:19 pm

Whichever one works seems to be dependent on which one was turned on first
I read that somewhere else too. I seem to recall it was something related to DHCP. So the place to start would be ensuring that each Pi is receiving an IP address and is ping-able. Look in the system logs (both the server and the Pis) to see if there are any error messages or DHCP refusals.

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