Yo.’re b.eaking up – ca. you rep..t t.at ?

Well, it seems like my power line networking gear is struggling to maintain a connection between my house and garage. Seems that it works for a while, and then the connection gets dropped for a while, before coming back again.  Rinse, Lather, Repeat. Unfortunately my industrial controller takes a very dim view of this behaviour, and gives up on its Internet connection fairly quickly, and takes its ethernet interface down. Which is a pain, given that it needs that connection to talk to the outside world. And worse, since my only way to talk to it is over that connection too, I now have to trudge out to the garage with my laptop and serial cable to get it back on its feet again. Which means that my plans to do interesting things with one-wire weather stations and sensor networks are back to square one again.

Having spent a couple of hours crawling over the mains wiring in my house and garage, I suspect the problem is that there are just too many electrical connections between the two transmitters, which are introducing too much noise (actually, probably just reflections) into the data signals. I suspect that it doesn’t help that there are significant differences in the way domestic properties are wired in the UK and the USA where power line networking gear originated. Of course, this stuff has now been standardised, so it *should* work … and indeed it does. Just not reliably out to my garage. Grrrr.

So, time for “Plan B”.  I have wifi coverage in the garage, but unfortunately as we know, the industrial controller doesn’t speak wireless – otherwise I’d not have bothered with the power line stuff.  So the obvious alternative is to go for a wireless bridge, which will produced a wired Ethernet connection from my wireless system. Now, you can buy these off the shelf – which is good.  But (you knew there was a “but”?) they tend to be very expensive for what they are, and often perform quite poorly. So as an example, the Linksys WET54G is around £60 ($120) delivered.  Not impressive, given what a simple job it does.

So the geek in me says that there has to be a better answer (oh oh … this is how I got into this mess in the first place) … and there is. You can buy a Linksys WRT54GL wireless router for about £45 delivered. And then you can reflash it with an open source firmware based on Linux … check out OpenWRT.  And all of a sudden you have total control over a little device with an Ethernet port, a fully programmable 4 port Ethernet switch, and a wireless interface, with full support for VLANs, bridging, and even VLAN trunks.  And the icing on the cake?  This thing has two serial ports on the circuit board that aren’t normally exposed … but that are usable under OpenWRT.  And you can cross-compile and install your own packages!  All of a sudden I may not need to use my industrial controller any more … I might be able to get away with plugging a one-wire to serial converter directly into the WRT54GL, and monitoring the one-wire sensors and weather station directly from the WRT54GL.

I’m itching to order one. But once bitten, twice shy … doing a little more research this time.  And if you’ve any experience of OpenWRT, please post a comment.


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