Adafruit delivered my Beaglebone Black today. Wow, what a fun piece of gear! First the Raspberry Pi, now the Beaglebone Black. In a couple of months there will probably be a new ubber-toy, but for now this is the neat stuff.
Beaglebones have been around for a while but the price of around $90 seemed pretty steep once the Raspberry Pi hit the market for $35. The just released “Black” is just $45 and it includes an Angstrom Lunux install on 2G of on-board memory (plus 512M RAM). The processor is a bit faster than the Pi but what really sets it apart are the i/o headers. This thing looks like it can connect to everything at once. There are 65 GPIO pins ! Configurations include the capability for four RS-232 ports, 2 I2C ports, seven analog inputs, multiple timers and PWM, etc, etc.
The other thing that sets this apart from the RPi is how quickly you can bring it on line. Depending on the Linux image, the Pi will have to be hooked to a keyboard and monitor for set-up. After that you can set up some remote access like VNC to work with it over the LAN. The Beaglebone Black includes a USB-to-mini-USB cable that plugs the Black right in to your PC. The USB provides the system power and the Black will show up as a disk drive file folder. All of the manuals and instructions are right on the device.
The next step is to install the special drivers for your OS. Be warned that if you are running Windows 8 you will need to go into the special start-up mode to allow the Beaglebone unsigned drivers. Once you have the drivers running, more awesomeness is in store. The Black is running a web server that you can access with your PC browser. From there you can write and debug programs, and even open an SSH connection through a terminal emulator.
Fuse and it’s location on the PCB. Cutting tool at left.
So, a few posts down the list I mentioned how I fried a diode in a 5 volt router by trying to feed it 12 volts. The router is back in good order, but the diode failed by presenting a dead short to ground. Yep, the power supply, insulted by the router’s request for infinite current, ceased to function.
For some reason these 12 volt power supplies, “wall warts”, are hard to come by at the local Goodwill store. It seems like every time I go in there I come out with another router, but no power supply. I decided to see if the PS had a replaceable fuse inside. The case was very permanently glued. No amount of prying would loosen it, and the danger of a mishap with a knife blade led me to another option.
A few months ago I bought an electric “oscillating tool” with a cutting blade from Harbor Freight for about $12 because it was darned cheap and I KNEW I would find a use for it some day. That tool made short work of the three seams around the PS (I left the cable exit side alone) and in no time I had the patient flayed open. There was a little PC board next to the transformer with a shrink-tubed fuse mounted vertically on in the path of one of the secondary windings. It was open alright. I removed it and replaced it with, in this case a 3A slow-blow which I insulated with a piece of electrical tape. I closed the patient up with some black Duct Tape and returned him immediately to service.
I have been spending a lot of time messing with mesh routers. To avoid the hassles of plugging/unplugging cat-6 from my desktop PC I had been using a laptop. The desktop with the big monitor is a lot more comfortable hacking platform however. I bought a GWC USB/Ethernet dongle from Newegg a couple weeks ago and I am very happy with it. At the time it was on sale for $10 with free shipping but I think the regular price is about $13. What this lets me do is leave my tower PC in place with it’s usual Ethernet connection in back, while I can plug the dongle in to a front USB jack when I want to play with the mesh toys.
The dongle was recognized right away by Windows 8 and Ubuntu 10 with no additional drivers needed (but they are included). Windows can be kind of difficult (at least for me) when you have multiple Ethernet cards as far as changing routes, IP addreses, and such. I set up a Mint Linux distro VM in VirtualBox to use as my “mesh playground”. All you have to do is tick the Ether-Dongle box in the VM menu USB section and it will light up in the VM (and disappear from Windows). While the network connection works fine in Linux, it is not recognized in the Netmanager GUI as a network device. It does however respond to command line utilities like ifconfig and route.
“Radio Mobile” is a terrific radio path analysis program by Roger Coudé, VE2DBE. Unfortunately it’s great power comes with great complexity of the user interface and all of the options and parameters. Thankfully Roger now offers a web based version of Radio Mobile which lacks much of the customization of the standalone freeware, but is much easier to use for quick analysis. Just head over to http://www.cplus.org/rmw/rmonline.html and register for a password. In a few minutes you will receive an email with your password which you will use to log in and operate the software. Having a log-in is a great feature, because it allows you to store your site and link details for ready access in the future.
This is a screen capture of a coverage map that I created with Radio Mobile Online. I wanted to get an idea for what kind of point-to-point links I might be able to make with a UDR56K4 radio so I set the SITE at my QTH and in the COVERAGE section I used 440 MHz, 20 watts, and an 6db omni antenna at 8 meters AGL. The MOBILE section specifies the other end of an RF link. Since I was interested in the path from me to other fixed stations, I also specified a 6db antenna at 8 meters.
No path simulator is going to have all of the terrain and obstruction data that has a real effect on your coverage, but it is very nice to have a ballpark estimate of what you MIGHT expect. Note that the online version is limited only to Amateur frequencies, which are noted in the HELP section.
I have been playing with cast-off consumer routers for the past few weeks. I have amassed a few, and been in the habit of leaving the 12 VDC cable at the ready so I can quickly pop one on line to use. I have a small pile of routers now, MOST of which are 12 volt devices.
Now with custom graphic on the side to remind me… 5V!
Tonight I pulled a Buffalo off the shelf that I had previously flashed with OPEN-WRT firmware. It is not supported by the commonly available ham mesh firmwares, so I wanted to tinker a bit and see if I could make it play on the mesh. I plugged it in and the lights flickered for a bit, then all went dark. Hmmmm. Wrong sized barrel plug? Nope. Power supply dead? Nope- 12 VDC on the meter. I read the sticker on the router- “5 volts DC” D’OH! I was so used to 12 volt routers that I forgot there are a few out there that run on 5.
The new diode is just right of the DC jack
After prying open the router case, I was relieved to see a diode right next to the DC jack. Could it be that the Buffalo engineers included an anti-knucklehead feature? The diode read dead short both directions on the meter. YES! I didn’t have a schematic but I knew (now) that this was a 5 volt circuit so I replaced it with a 5.1 volt diode from my parts bin. Back in business
This is a picture of a decibel. They are very important critters in the ham radio world. Usually, the more the better- especially when you are discussing gain. For all the time I have read about them in spec sheets, I had never actually seen one until today.
Last week I ordered an omnidirectional 2.4 GHz antenna from WLANPARTS in Pasadena for $60. I was impressed (and a little suspicious) that they could pack 15 db of gain into an omni antenna that is only 41 inches long. Regardless, this “house brand” unit is cheaper than the competing 9-10 db units, so why not give it a shot?
A few minutes after the UPS truck left I had the antenna disassembled to see the magic. The unit is solidly constructed with a fiberglass radome over a 15 element collinear array with a female N connector on the aluminum base section. Mounting hardware is included for attaching to a mast. Scouting around the web I discovered that a 15 element array like this one should have about 9-10 db of gain. A similar figure that is claimed for competing branded omni antennas of comparable length. I suspect that the marketing guys opened one of these up and figured, “Those little do-hickies must be the decibels…. there are 15 of them… Wow! Our antenna is way better than the competition!”
Dubious gain figures aside- I think this is a decent antenna. I have not exhaustively tested it, but it is sturdy and clearly boosts indicated signal strength in my brief use. The fact is you probably would not want much more gain in an omnidirectional antenna. You don’t get something for nothing. Antenna gain comes from shaping the pattern, so the greater the gain, the less vertical beamwidth you have. Unless your antennas are at the same elevation, they might “beam” their signals over and under each other. So, if you want to boost your wifi signal around your property, do NOT mount this thing at the top of your tower
On the bright side, my MESH network is bound to expand geographically because I am going to run out of physical space for the nodes. I now have the pair of bullets that I started MESHing with last month, supplemented by three WRT routers that were rescued from the Goodwill store. Once they hit critical mass, I will start foisting them on members of the MBARC Digital Group. I am not sure when that will be. I am still getting a thrill from watching the metamorphosis from cast-off “slow” router to high-speed ham radio ubber-toy.
There have been a few local people climbing on the bandwagon, and a few tire kickers. I added a MESH page on the MBARC /Digital Group page which has a link to a Google Drive spreadsheet for interested Whatcom / San Juan area Meshers. If you put your address on the spreadsheet you will be marked on the accompanying map to help find potential node links. The information column (2) appears as a tool-tip in the map view.