Embedded Linux and Amateur Radio

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Good day all,

I am currently brainstorming on developing and implementing a amateur network in our region (northeast Oregon, southeast Washington), to include using 802.11 devices running under US FCC part 97 regulations, similar to Green Bay Professional Packet Radio:

    http://www.qsl.net/n9zia/

But, having had some very positive experience with commercial outdoor 802.11a/b/g access points built around Linux single board computers (SBC), I'd really like to move in that general direction. That is, I'd like to build a system with no moving parts, using Linux as the operating system, with miniPCI 802.11 radio cards, and having serial ports to support KISS or 6PACK on TNCs. I'd like the ability to run LinuxNode at the least, or preferrably (X)Net. I'd imagine that the latter would mean that the CPU would have to be x86 compatible, since (X)Net is not open source and only binaries are available for it. The ability to compile the kernel is almost certainly a must, to roll in AX.25 support, etc. Since some of the sites are fairly remote and inaccessible for six months of the year, stability and reliability is an absolute must. For that reason, I'm leaning towards the 2.2 series kernels, as my experience was that it was always rock solid with AX.25 compiled in -- although I did just have 190 days uptime on my gateway with 2.4.24 before it inexplicably rebooted (power bump? -- my UPS is shot).

Has anyone already expended some energy along these lines, either time on the drawing boards, or actually spent building such a system? Any words of wisdom? It would be much appreciated.

73 es tnx,

Brett Mueller, WA7V

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One of the niftiest ideas I can think of in this realm would be to use a Linksys WRT54GS access point as a Linux Packet device. It runs Linux, with OpenWRT firmware you have a fully read/write 6MB filesystem in firmware, and you can easilly hack on two serial ports to talk to external TNCs (although I'm not sure they support hardware handshaking). Oh, and it would remain a 6-ethernet-port Wifi device. :)

http://www.rwhitby.net/wrt54gs/serial.html

That hack would be slashdot-worthy, and probably not TOO hard. :)

Braddock Gaskill
Writing this through a reflashed BusyBox Linux WRT54G...

I think so too. Sometime soon I want to move my APRS gateway (running aprsd) onto the Linksys with the TNC connected to a hacked-in serial port.

That may mean recompiling the 54GS kernel to add AX.25. Has anyone done this already?

Hamish

Hamish Moffatt VK3SB <[email protected]> <[email protected]>

Ahh, now I do not feel so bad, I had this somewhat perverted dream of doing the same thing... Multidrop kiss would allow you to have more than one TNC hanging off of the thing... If 6pack for Linux is fixed for multiple tnc's then it would be even better....

Chuck Hast 
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going
out and having to identify your bits and pieces in the midst of torn
and twisted metal."

Hi there,

I've been working on a project in work for the last few months. I've based my work on cqureap Linux Wireless Access Point

and as well updating all the packages and changing it to write a Compact Flash Image (instead of floppy), It's relatively straightforward to add any package thats required.

For work we are building a Linux Access Point and adding intrusion detection functionality, using Atheros PCI/PCMCIA Cards (great cards btw, real good for backbone links as well at 5.8Ghz).

This week I'm in London trying to co-ordinate with others at an Integration/Project Audit event.

I'm currently using the EPIA MII10000 motherboard

If anyone is really interested I have a draft document explaining (to myself) how it all hangs together, and if someone is really interested I could send them the draft.. but its not of good quality.

My own plan is to take what I've learned, and make a CF image that would allow me to put Digi_ned/java aprs server on a box and use it then as an APRS Node/Igate OR, I might just move to using a picotux, I've not really decided yet.

Regards
de John
EI7IG

P.S. I've re-sent this with all urls removed... the last one got blocked.

The last time that I was in Wal-Mart, the WRT54G (no S) model is down to $58 now too...

FYI, the Sveasoft Talisman firmware is really nice.

Mike

I've ported Xnet to MIPS; it's been demonstrated on the Packet Radio Congress in Darmstadt in April running on a WRT54G wireless access point.

In such a case you want a watchdog or remote reset facility anyway. And a machine that minimizes mechnical parts such as fans.

For that reason, I'm leaning towards the 2.2 series

Pure luck. The kernel AX.25 was and is full of potencially fatal bugs.

The wisdom says use proven OTS components :-) It may not be as fun as homebrewing but minimizes potencial points of failure.

73 de DL5RB op Ralf

--
Loc. JN47BS / CQ 14 / ITU 28 / DOK A21

Hi, Brent -

I've spent a lot of time trying to get a small version of linux running on a Soekris Engineering single-board computer (http://soekris.com),
with the intent of running packet radio through it. Ultimately it will be the communications payload for a weather balloon, similar to what Jim Meehan did at http://vpizza.org/~jmeehan/balloon/.

I thought the tough part would be getting the OS running - not so. I'm using Bering 1.2, which runs fine by itself but has no way to rebuild the kernel - no make, no gcc, no nothing. I'm trying to build an ax25 module on another machine, but I'm a kernel-building newbie and I'm scratching around in the dark.

If you *do* come up with something, please share! And if anyone out there has tried what I'm trying, or has a better suggestion, please chime in!

Thanks, and good luck!

Patrick Koehn

There's lots of vendors with boards like this. Though I haven't used any of their stuff some of the local guys are fond of Soekris (www.soekris.com) for hardware hackery projects. Soekris seems to be a small house with pretty sharp people, and their stuff is inexpensive. Their 4526 board seems made for your project.

De

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On 6/21/2005 10:34, I wrote, in part:

<snip>

Hello everyone. First off, thank you very much for your responses, both on list and off. I really appreciate them. I was directed to a number of good resources, some which I had previously found, and others that I hadn't. As I read some of your replies, I realized that I had neglected to mention a key fact that can significantly impact my selection of
hardware: the project has a decent level of funding. As a ham, I know what it's like to come up with solutions on a shoestring budget -- oftentimes "it may not be glamorous, but it works!" In this case, however, I have access to a number of prime public safety sites, and can spend a bit more on equipment than the average ham can cough up (certainly more than I could on my own). Also, equipment installed in those locations must be professional in appearance, and meet standards for grounding, lightning protection, etc.

For other (non-ham) projects, I have used Demarctech outdoor access points, which have a nicely laid-out Linux-based system (StarOS Router) on a PC Engines WRAP board (AMD Geode CPU).
http://www.demarctech.com/products/reliawave-rwv/rwv.htm
http://www.staros.com/
http://www.pcengines.ch/wrap.htm
For this proposed ham project, I was envisioning something similar, while adding the ability to load amateur-related software on the system.
I'd like to be able to have dedicated point-to-point connections
between the sites, perhaps on 5.8 GHz where possible. This would preclude using the WRT54G for those links, although I can see great possibilities for the Linksys unit elsewhere -- particularly other "peripheral" sites that don't have the "funding" resources available. Thanks to those that pointed out the great capabilities and hackability (in the old traditional sense of the word) of the WRT54G.

Compact flash cards certainly seem like the way to go (as per my original criteria -- no moving parts), but I think I'd probably invest in a CF - IDE adapter (especially if I went with an x86 based solution) so that I could compile/install/test from a faster machine.

Power-over-ethernet (POE) is great stuff, too, where you can easily mount the SBC / radio in an outdoor enclosure, use a meter or so of feedline to minimize your losses, and run some relatively inexpensive UV-rated CAT5 down the tower and into the facility (through lightning protection, of course).

Ralf's MIPS port of (X)Net also opens up other possibilities, having the option of using it on SBCs based on the MIPS architecture. He also correctly points out the inherent problems in the kernel AX.25 code, and I came to the realization that AX.25 support in the kernel would be unnecessary if (X)Net was running.

I like the looks of the Soekris boards that a couple of people pointed me to. I'd like to find one with dual Mini-PCI and dual serial ports, but I'm not seeing it. (hmm, will (X)Net do something like MKISS?) Nevertheless, great possibilities there.

Paul directed me to a "smallish" distro called Pebble Linux. Their page also includes good information on setting up a Soekris access point:
http://www.nycwireless.net/pebble

I'll keep sorting through the information out there. Thanks again...

73,

Brett, WA7V

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In the end I however consider usermode stack integrated with a whole set of applications and server daemons such as Xnet a design mistake for operating systems such as Linux that are pretending to have full blown and universal network stacks and I'm working - time permitting - on getting the kernel stack to work just as well. Nontrivial, challenging - and hopefully at some point - also rewarding ...

Ralf

In the case of the WRT54GS, I'm concerned that it will be running linux 2.4 yet AX.25 (from what I've read) was never too good on 2.4.

I want to run an APRS gateway on it and aprsd can work with just a serial port to the TNC, but I prefer the AX.25 method. (And I might want to switch away from AX.25 at some point).

I don't know if the WRT54GS could be upgraded to 2.6; I think it has some proprietary (binary-only) drivers for the Broadcom wifi chipset.

Hamish

Hamish Moffatt VK3SB <[email protected]> <[email protected]>

Quoting Hamish Moffatt <[email protected]>:

[...verbiage clipped in the name of brevity...]

I am aware that the WRT54GS (and many other of the some several products that Linksys makes) use a Linux Kernel for their firwmare. However, I have not yet secured time to review the released source code for these kernels. If the Wifi drivers for the Broadcom Wifi adapter inclusive to a particular Linksys product are something other than a loadable module (supplied presumably in binary format only), i.e. are written into the kernel, and Linksys has not released the kernel inclusive of said source code for the Broadcom driver, then I would contend that their is a potential cause of action to force Linksys to release the Broadcom Wifi driver source code!

Or are you saying that the Broadcom drivers are being supplied as loadable modules in binary form?

I do not own a 54GS, and therefore have not reviewed the source code and firmware releases.

Just some food for thought!

IT3 Stuart Blake Tener, USN (RC)
Beverly Hills, CA
(310) 358-0202
teners at bh90210 dot net

Nor probably are you a copyright holder. Initially Broadcom wasn't shipping source code at all, a group of Linux copyright owners, including me, and the FSF negotiated the issue with Broadcom. In the end they did release a very comprehensive tarballs of source code, tools etc. which should even to a newbie permit rebuilding the code.

The only problem were the wireless drivers; the Japanese regulatory authorites, the MIC, has some regulations that basically prohibit opening the access to the transmitter controlls such as power and frequency. The FCC's rules could be interpreted in similar ways and so in the end we agreed on this being a fair compromise.

73 de DL5RB op Ralf

--
Loc. JN47BS / CQ 14 / ITU 28 / DOK A21

I recall that early 2.4 (<2.4.18?) kernels had problems with AX.25, but I have been running a DX Spider node with 2.4 kernels (currently 2.4.26) for quite a while and have not experienced any AX.25 difficulties.

Bob, N7XY