Not entirely unlike a Kaplan turbine, my mini-turbine is used in a high-flow, low-head(room) scenario. Only in reverse, sort-of. Confused? Perfect, mission accomplished :-)

I got fed up with the silly WAP-11 wireless access point and its lack of support for WPA; wanted to have faster wireless and not absolutely have to have openvpn on top of it. A few weeks ago I noted a discussion of the evilness of Fon (example one and two) which also mentioned that Fon's subventioned wifi access point (La Fonera) is dirt-cheap and works with OpenWRT, an open distribution for such hardware (originally only for linksys WRT's, hence the name.

Perfect: more hackvalue, new fun, embedded gear to experiment with and yet another box that runs something unixy, which can't be bad by definition. It also brings my linux-covered hardware architectures up to three-and-a-bit: Intel, Intel-but-embedded/crippled (netvista), (Ultra)SPARC and now MIPS.

So I got me a new Fonera for AU$10 and started reading up on it.

First one needs a 3.3V-to-RS232 converter to make the serial console accessible; the usual 10min soldering job and a max232. I stole the power from the main supply which is conveniently +5V (the power pin on the serial jumper pad is only +3.3V, not enough for a normal max232). Some sources claim that the fonera doesn't boot if the TX pin is connected during startup, but I can't confirm that: mine starts fine and fast, no matter what.

Second, one needs to think about cooling: the Fonera case is...marginal in that regards and many people have complained about heat problems. I had an old Dlink AP carcass sitting around, and a 5V fan from a gutted lapdog. That was also beneficial, because I immediately soldered in an extra antenna onto the second pad for diversity (not that I need it for my setup, but shouldn't hurt) and all of these extras wouldn't have fitted into the Fonera case, ever. Even with the Dlink box it's Very Little Headspace Indeed and I had to cut out an intake hole for the turbi^Wfan. The fan is quite sucky and somewhat loud and therefore the box is named turbinchen (German for small turbine).

Finally, one has to find one of the many, slightly misleading and often outdated sets of docs that describes a working procedure for flashing the OpenWRT firmware over the Fonera one (which is openwrt-based but crippled and with lots of Fon-evilness thrown in). Of course I bricked it straight away, but thanks to the goodness of RedBoot (the open bootloader which lives in flash and simply rocks) the recovery was a trivial two minute job.

This is a nice description of the hardware options for getting a serial console, but in German.

Here is the official doc on OpenWRT on the Fonera, which is mostly correct. The explanation on how to get a backup of the Fonera firmware is wrong: the httpd is not silly enough to read block devices for you. This explanation of the initial mtd partitions is better, covers a working way for backup and also methods of gaining access without a serial console.

In the end I simply nuked the Fonera firmware without backup and went with this very nice German howto. Overall the procedure wasn't overly bad, but the lack of authoritative and up-to-date info covering the OpenWRT guts was annoying. All in all it took me only one evening from start (ripping things apart, soldering up gimmicks) to finish (WPA2 with suitable regulatory domain settings, remote syslog etc. etc.).

Here are some obligatory photos of the finished product.

 2008_04_03-turbinchen-open.jpg  2008_04_03-turbinchen-top.jpg
[ published on Fri 11.04.2008 12:18 | filed in interests/tinkering | ]
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© Alexander Zangerl