The Austringer

I had the chance to work with my Raspberry Pi some more late last night and this morning. Quite a lot of stuff works, given that the board design is essentially at a state of “ready for the software developers to do their thing”. But some things are not quite there, or behave oddly.

My first boot-up that I talked about was on a bench without networking. That turns out to be significant. When I tried to run my RasPi with the full load of peripherals in the USB hub and also have the wired Ethernet on, I got a lot of “kevent 4 may have been dropped” error messages and no network connection. The canonical answer on the RasPi forum is that this is a power supply issue, where marginal power to the board means there isn’t enough to properly run the Ethernet circuitry. Some respondents have noted that their circumstances don’t fit into that neatly. I suspect that I may be joining them, but I have some more experimentation to do before saying so categorically. My get-it-working solution so far is to run the RasPi off a dedicated power supply and have all the peripherals on a powered hub. This isn’t ideal for something I hope to deploy remotely. I need to figure out really reliable, comes-up-on-power-on every time configurations.

I spent entirely too much time dealing with something that I should have caught early. The RasPi is a UK invention, and its default settings are convenient for people in the UK. I have a firewall here, and I set my RasPi to enable SSHD so I could login over the net. I logged in from an Ubuntu box and changed the “pi” user password to something approaching a strong password, you know, one with odd case, numbers, and symbols. That’s all to the good, but then I rebooted and ran into the network interface being offline. Fine, I thought, I’ll login directly. But I couldn’t, because no matter what I did, I could not generate one of the symbols in the new password from the directly-connected keyboard, not even with alt-codes. Stripping the RasPi down to just power and network allowed it to boot and establish the network interface, and I could login once again from a remote computer. I changed the password to avoid the bad symbol and worked on localization. The involves “dpkg-reconfigure” applied with three different targets, the keyboard, the locale, and the timezone.

I’ve been able to install a batch of additional software. I installed Cmake and libncurses5, then tried building Avida on the RasPi. The Avida build doesn’t get far. tcmalloc apparently is known to have build issues on ARMv6, plus multiple classes got an “out of virtual memory” error. That still holds with the boot switched to the 224MB main memory setting. But python-scipy and python-gps installed without issues. I even installed VLC to check if the final piece of a media center was anywhere close to done. While the VLC and its dependencies went on without complaint, plugging in a USB DVD drive and pointing VLC at it did not go much of anywhere. There was no continuous playback, and if I changed the media pointer, it would display a single frame. I think that the color rendition was off, but I had plugged in a movie that I hadn’t watched yet, so it is just possible that the cinematographer thought a strange palette would be a good thing.

I tried out my USB GPS dongle. I installed “gpsd-clients” and ran cgps, which reported … absolutely nothing. That was disappointing. I plugged the GPS into my Ubuntu box, and cgps happily displayed a fix and chatter from the dongle. I went back to the RasPi, stopped gpsd, then used gpsmon. That displayed a fix and messages from the dongle. So I’m not sure why gpsd on the RasPi is doing things differently than on the Ubuntu box.

For those pulling up “Geany” to do some Python scripting, you’ll need to change the preferences so that the terminal of choice is not “xterm”, but rather “lxterminal” (this is for Debian Squeeze).

That’s it for now. I’m expecting to have to repeat this process whenever a new version of the operating system is released, so a set of notes on what gets done seems in order.

Notes on RasPi

Adding nameservers:
sudo nano /etc/resolv.conf
nameserver 4.2.2.2
nameserver 4.1.1.1

Localization:
sudo dpkg-reconfigure keyboard-configuration
sudo dpkg-reconfigure locales
sudo dpkg-reconfigure tzdata

Additional python modules:
sudo apt-get install python-scipy
sudo apt-get install python-gps

WiFi dongle —————————————–
See http://elinux.org/RPi_Peripherals

Add to /etc/apt/sources.list:
deb http://ftp.us.debian.org/debian squeeze non-free

Then
sudo aptitude update
sudo aptitude install firmware-atheros

cd /lib/firmware
sudo wget http://wireless.kernel.org/download/htc_fw/1.3/htc_9271.fw
sudo wget http://wireless.kernel.org/download/htc_fw/1.3/htc_7010.fw

I got email from Newark today saying that they had shipped my Raspberry Pi. I should get it this week.

They also sent an invoice, having charged my credit card. The item itself is $35.00, shipping is $5.00, and tax is $2.28, for a total of $42.28. Way back in early March, I called Newark to place my order since someone noted that the huge shipping charge they were quoting at the time could be avoided with a phone order rather than an online order. Hopefully they’ve fixed the online ordering since then.

Otherwise, I think that I have enough RasPi accessories to get started with when it arrives. I picked up a used Tektronix oscilloscope and an LCD monitor with DVI interface from Mario DeSario at Audio Workshop in Bradenton, Florida. I have a HDMI to DVI adapter and an HDMI cable. I have a 2.5 amp powered USB hub to supply the RasPi and allow me to plugin more accessories. I’ve got a USB GPS and a USB sound interface. I’m looking forward to diving in on this.

I also saw on the RasPi forums that by installing Mono, a RasPi can run executable files produced in managed .NET code from Visual Studio. That is a cool capability. I might try doing the monitoring system software in C# and .NET.

I still need to do some work on the hydrophone side of the system. I want to do a bit of home-brewing there. Years ago, I heard Cornell’s Chris Clark talk about fabricating in the field what he called a “schlong-o-phone”, which was basically a microphone capsule potted in epoxy in a convenient flexible cylindrical latex mold, otherwise known as a condom. Some of the more convenient materials for filling a mold don’t actually work well for salt-water and electronics. For example, most RTV (silicone) formulations are waterproof in themselves, but do not bond well to cable insulation. Additionally, the relatively high viscosity means that best results require applying a vacuum to de-gas an RTV mold, and that’s outside my current state of gear. I’m going to experiment with a piezo disk and Plasti-Dip. I’ve priced urethane for molds, and it is indeed expensive, but it is also low viscosity (no bubbles in the mold) and should bond nicely to cable insulation. If the Plasti-Dip results are bad, I’ll likely give the urethane a try.

Checking stuff out will require at least a couple of the home-brew hydrophones, our trusty frequency generator, and the oscilloscope. I have a variety of pre-amp and amplifier DC-powered circuits to pair up with the hydrophones.

Something I’ve wanted to try out for years now is doing a reciprocity calibration, but I’m not quite there yet, either. Reciprocity calibration uses three transducers (whose characteristics may all be unknown) and yields an absolute calibration of a receiving transducer. If a transducer can serve for both receive and projection on short time scales, a self-reciprocity calibration can be done. In either method, precision measurement of the current going to the projector in the system is necessary. That’s the part that is most challenging. There are plenty of other challenges, though. For hydrophones, the distance between all the transducers needs to be enough to be in the far field, where spreading loss is predictable. At least a meter to 1.5 meters is what would serve as a minimum. Then, one needs to be far enough away from either the water surface or any other obstacles so that the calibration signals aren’t bouncing off other things and giving reverberent noise that would compromise the received energy levels. 1.5 meters distance from other surfaces would give about a millisecond’s worth of unblemished sound. So we’re talking a quiet body of water at least 4.5 meters wide by at least 3 meters deep just to get a millisecond of calibration data at a time. I think I’ll have to defer home-brew reciprocity calibration for a later date.

I have owned several Canon digital cameras in the point-and-shoot through prosumer range. Something Canon has offered for a long time is the Canon Loyalty Program. This allows one to obtain a refurbished Canon digital camera at a discounted price when one trades in a Canon digital camera. Unfortunately, I’ve never had much luck finding current offerings via Canon’s website. So a little while ago, I asked on the phone what refurbished cameras are currently available and at what price. I will provide the list in a table. I wanted to collect all the ancillary information, but my life is still pretty hectic now, so I’ll put up what I have and add to it as I get time (if I get time).

To take advantage of the program, call Canon at 866-443-8002.

I attended the 2011 Consumer Electronics Show in Las Vegas, Nevada last week. Lots of articles are out there concerning the general tenor of the thing and the hot topics. In summary, the show is still The Big Thing for the consumer electronics industry, with upwards of 130,000 attendees. The exhibitors are thinking that mobile computing, especially with tablets, is going to continue to be huge. For entertainment, makers of monitors, TVs, and video projector systems all are convinced that 3D is going to finally achieve the big market acceptance they’ve been pushing for lo these many years.

The show itself took up the entire Las Vegas Convention Center, all the halls and all their levels. There were exhibitors also at the Hilton and the Venetian hotels. Having so many attendees come into Las Vegas put a bit of a strain on the transport from the airport; I heard reports of fifty minute cab rides for the trip. Putting all the attendees into the halls with the exhibitors made for quite the crowded experience. I don’t recommend it to people who get upset about intrusions into their personal space. There is simply too much show for any one person to survey it completely. Of course, most attendees will have a fairly narrow set of high priorities, which helps cut down on the number of venues and halls to be visited.

Compared to past shows, there was far less distribution of promotional goods and even a lot of cutting back on providing printed materials. Some places provided quarter-sheet cards pointing to websites with information. This points to a tightening-up of the market, I think. One conversation I overhead at a middle-sized exhibit was that the exhibitor had spent about a million dollars to come and present at CES. They did have printed materials to hand out, I should note.

The opening day “CES Daily” magazine had an article noting that the industry should be putting effort into promoting science, technology, engineering, and math (STEM) education. There were a couple of exhibitors I noted who had education in mind in their offerings, but it is tough to gauge commitment to science education from a trade show. Hopefully, the attendees and exhibitors paid some attention to the article. If innovation is what is looked to for saving economies around the globe, preparation in the educational system is a critical component to enable that to happen. Here in the USA, I think there is way too much complacency, with our past record of technological prominence luring people into a comfortable sense that things will continue in that way. They aren’t doing so, and it is time that we acted to correct the downward trend we have concerning STEM education and career choices.

I’ll be posting about specific things I saw at CES 2011 as I get both time and my photos processed.