Random notes & other stuff…

Cisco 1841 ADSL configuration for Free telecom

(a french translation for this article is here)

http://leucos.lstilde.org/wp/2009/05/cisco-1841-ads…r-free-telecom/

People connected via Free, a french internet provider are usually happy customers… until they need to get support. Well, this is a problem with most of providers out there.

When you subscribe to Free, they send you a Freebox : a combo containing a DSL modem, a router, an FXS to hook your telephone, and sometimes more if you’re lucky enough to have TV and other services.

But when you don’t want to use this box, or when it’s dead, you can use alternate ways to get connected. The easiest one if to get a DSL modem (a speedtouch for instance), and use a PPPoE capable routeur (like a Linksys WRT54GL + tomato firmware).

You can also do PPPoA if you have a router with an ATM interface. The configuration included below can be used on a Cisco 1841 routeur with ATM card to connect to Free. It probably can be adapted to other models  very easily by changing only interface names.

You can debug what happens by issuing :

Good luck.

High-power TVBGone

This TVBG has been done a long time ago, but I never took time to write about it. It’s quite powerful : you can easily take off TV’s at 100ft, and even works thru your pocket (and pretty far if you wear GoreTex). But guess it, with power comes batteries, and the downside is it’s size, roughly the size of a cigarette pack (all the pictures below are pretty outdated…).

TVBGone with it

The design is pretty simple : an AtTiny85, 6 TSAL 6100 IR diodes from Vishay (rated 1A for short pulses), 6+1 NPN transistors. Unlike what is show in the picture below, there is no more jumper (it was used to switch between programming mode and run mode). The tantalum capacitor has been scrounged, and not bought. If you know what coltan is, you know that buying tantalum stuff is rather bad.

TBGone bottom viewTVBGone with it

The thing is powered by 3xAA batteries. There is no current limiter, the only limit is provided by the batteries internal resistance so take care if you want to change supply for a LiPo or whatever, you’ll blow the LEDs for sure. In this case, add a resistor along each LED, or better, use some current regulator.

For now, the 6 TSAL LEDs are sucking 2.5 Amps without a current limiter.

TVBGone top view

The AVR code has been found on the net, and is provided here almost unmodified. The original authors are in the main.c header file, among which, of course, Limor (aka Ladyada).

I’ve changed the IR codes a bit, removing some duplicates, reordered them too so the most used codes comes first (file with modified codes is PERSOcodes.c).

One of the problems is that LG TV can not yet be turned off. This is a pain since LGs are everywhere. I don’t have time to reverse engineer timings for LG or use convert Lirc codes for now. But for sure, this would be valuable work. If you do it, please drop me a note.

EDIT : CaitSith2 dropped a note saying he has more up to date code for TVBG which turns off LGs too (see comments). So you’d better use his code than mine. Thanks CaitSith2 !

EDIT2 : It seems that CaitSith2 is more high power : 8 TSAL6100, 4xAA… nice !

In the schematics (tvbgone2_cms), all the little pads near JP1 are for a very weird slide button (I was too leazy to draw an eagle lib part). So don’t panic and adjust for your switch.

There is another schematic included : tvbgone_mini.sch, which is a variant intended to be build as jewelry. I plan to use CR2477 batteries but I never built it. If you make it, please tell me how things turned.

The P & R pins are « Program » and « Run » respectively. When done programming, just cut the wire going from the central pad to P, and make a solder bridge between the central pad and the R pad. If you need to reprogram again, remove bridge, and bridge between the central pad and P, etc…

Get the eagle schematics, grab the code, turn off those TVs and have fun.

Fixing ‘IPSEC(initialize_sas): Invalid Proxy IDs’ with dynamic VPNs

Dynamic VPNs is a Cisco feature that makes a central router accept VPN establishment without specifying a peer or an ACL for the SA.

The configuration is very simple (even simpler than normal, statically specified tunnels) so when the tunnel doesn’t come up, it is quite frustrating.

And when you get ‘IPSEC(initialize_sas): Invalid Proxy IDs’, meaning SA ACL doesn’t match on both sides, you start to pull your hairs out : how can’t they match when they are not needer on the headend side ??

Well, it seems that the headend is checking the remote SA specification (Proxy ID) anyway, and bails out from isakmp when things go wrong.

Consider this log, saw on a router sitting at 172.22.1.130/27 with

and

See it ?

the subnet mask 255.255.255.193 comes from a wrong ACL specification :

instead of

So 255.255.255.193 last byte yields a discontinuous mask (11000001) which is not so commonly used
That’s why the tunnel is not coming up, and how you lost the last hour.

WRT54G/GS/GL Relay Mod

Sometimes, it could be handy if your router (in this case, a WRT54G) could restart the device that connects it to the internet. For instance, if your ADSL modem needs some reboot or your cable modem needs a kick, having the WRT to do this would be nice.

This could be especially useful if the modem+router are deployed as an access point somewhere in the wild.

This usage is not limitating : we’re gonna build a WRT managed relay. What you switch on/off with this relay is your problem. A modem seems a reasonable idea, but you could switch a coffee pot (in this case, you should go with HTCPCP [http://www.ietf.org/rfc/rfc2324.txt]), lights, etc…

All this is possible with little modification. The behaviour of the system here is to switch the relay for approx. 14 seconds, but this time is also easy to change. You can even use a trim pot instead to make it fully tunable.

Schematics

Relay board schematic

The schematic is rather simple. The board is connected to the internal WRT54G serial port (TX pin). This pin uses LV-TLL signals (0, +3.3V), and logic high is 0V. In other words, when nothing is send out to the serial port by the WRT, the level is low and the TX pin show 3.3V. What we want is to activate the relay when voltage on this pins drop. The trick is to feed the TX pin to the Threshold pin of a 555 timer (see those excellent 555 links in Electronics Club and Mecanno Electronique in french). And this is what happens when we the WRT sends data to the serial port : square wave comes out of second serial port TX pin and triggers the 555. For this to work, the 555 is powered at 6V, and thus triggered when TX voltage drops below 2V (approx 1/3 of VCC). The 6V feed is very primitive and comes from WRT power (12V) sliced in half by a voltage divider. It would be wiser to use a voltage regulator (7805 or al.), but we’re going the easy way here.

The trigger from the 555 is fed at the base of the 2N2222 transistor which in turns feed the coil enough current to switch.

Primitive, as I said.

Assembling it

First, be aware that doing the bad things below will void your WRT warranty, your modem warranty. You also can burn things or yourself in the process, etc… So do at your own risk. This being said, that stuff has been my first electronics project so it is really easy. « my first electronics project » should also be taken as a warning.

• Open your WRT54G (or GS, or GL) by pulling the blue cover out

• Take the WRT PCB out.

• Solder a wire in the TX pin (pin 3) of the serial port

Soldering this port is really easy, even I did it without breaking anything or melting the router to a shapeless plastic blob. You’ll find more info and pictures on the LinkSys WRT5G/GS Dual Port Mod Page. You don’t need IDC headers or high end stuff like this. Just solder in the hole. It will be ok as long as you don’t pull too much on the wire.

The blue front cover has holes inside. These holes can’t be seen from the outside because of the stickers. This is a good place to make a complete hole with a hot wire if you plan to put your PCB relay outside the WRT. For recent models, like the GL, the PCB can probably fit inside.

• Pull the TX cable through the blue cover and assemble the WRT back

• Solder the wires with the DC power jacks on the board

• Cut power cables from modem and WRT. Be sure to cut it at the right place ! You need enough cable to plug the wall wart and enough cable to plug the modem and WRT.

• Remove some insulating material from the power wires and insert them in the screw clamps. Don’t mess with polarity or which wire go where. You would burn something for sure.

• Now we need software to get this going. The basic idea is to ping some IP address, and when consecutive failures are detected, the relay is activated and the stuff behind it reboots. You can push the shell script to the WRT running Sveasoft firmware under Administration/Diagnostocs/Run, then paster script and click « Save Startup ». You can do the same with OpenWRT and probably with other firmwares.

Tune variables at your liking. You can see how the relay is software activated : it just writes ‘ACTIVATE’ to the device driving the second serial port. What you write is not important. ’saddam’ and ‘george’ work equally well for instance. You should also restrain yourself from logging too much. The idel situation for deployment is to disable debug and logging. Space is scarce on the WRT.

Here is the final thing assembler, with the driver modem (a Terayon TJ720). The system works fine but is quite static sensitive. So discharge yourself somewhere before touching the running circuit, or the relay might activate. Also, proper casing should be done. Putting the circuit inside the WRT is possible with latter models (WRT54GS and WRT54GL). This hasn’t been tester though, and might put some noise inside.

Bill of materials

Building this stuff shouldn’t take more than 2 hours and if you wish to buy parts, it will cost less than 4€ (3.0€ each by 20 at GoTronic in France).

Here is the list of components required :

Besides the board and may be the 555, the rest is easily scavengeable.