Raspberry Pi Fiddling

Raspberry Pi

I'm sure you've heard of it.

700mhz ARM CPU, 512 megs of ram, OpenGL ES GPU, HDMI, 2 USB ports, I2C, SPI, UART, and GPIO pins. All in a single board computer that costs $35? Sounds like fun! So fun, I got one for christmas.

(that you santa)

Getting the Rasperry Pi Working

I should note that it really takes some other investment to get rolling with a Raspberry pi. You're going to have to put out for an HDMI cable, a powersupply, an ethernet cable, and USB cable, and a decently sized SD card. Also, I discovered that hot plugging my one USB keyboard between several computers and the Pi to be pretty tedious. If you plan on adding a lot of USB stuff, a powered hub to supply 500mA is going to be needed (my keyboard fades every now and then). A protective case might also be worth considering. Plan and additional $30-$80 worth of investment if you don't have any of that equipment

It took some experimentation to get mine to boot. (That's mostly because I didn't read the manual. ) Unlike a traditional x86 PC, it doesn't have a complicated firmware that preconfigures hardware and allows boot device selection. It just recusively drills the SD card for a bootloader and runs from there. No card? No Bootloader? No magic. Just a bright red activity LED and a dimly glowing SD card read light.

It's also very picky about where the bootloader is. The first time I downloaded the raspian disk image, I ran (on my mac)

%dd if="~/Desktop/2012-12-16-wheezy-raspbian.img" of=/dev/disk3s1 bs=10k

That process took forever and didn't work. After checking the cables and reading the manual, I learned that I need to overwrite the whole disk, not just the first partition, and that BSD uses a different syntax in that scenario: disk3s1 becomes rdisk3.

%dd if="~/Desktop/2012-12-16-wheezy-raspbian.img" of=/dev/rdisk3 bs=1m

Took just a few moments (read up on tuning dd's bs=* in your spare time. It will, one day, spare you time) and, when I plugged in and powered up the rbpi, i was greated with a massive screen load of linux booting goodness...

 ... and ultimately a desktop!

Raspberry Pi First Impressions

Fast computer, slow XWindows. 

Watching the boot speed, I was genuinely impressed. For how small and cold (temperature wise, it only needs 700 mA to start), it can really move. It's an amazing demonstration of how much power has been packed into chip packages through miniaturization. My enthusiasm was damped once I started X. The pi does not yet (at the time of writing) have an accelerated XWindows driver, so the GUI feels very sluggish at times. With some tuning, the fbdev driver can be made to feel somewhat snappy (using lightweight window managers and turning every single graphical flourish off), but for users not familiar with X and *nix, that's not going to be an easy option. The LXDE distributed with the Pi is a pretty good balance of usability and speed, but is not outright snappy. I think that puts user focused nettop duty out of the picture until X acceleration arrives. After being spoiled by compositing window systems for 8 years, and accelerated graphics for nearly 20, it's a little hard to go back. For programming and fiddling, It's definitely usable.

The raspian distribution comes with a heavy lean on python development, though there is a smattering of other compilers/interpreters present (C(++), perl, lua, bash), and if you're that kind of person, you probably know how to get what you want running. I was able to use apt to get emacs. As far as going from just a cute board to a cute board that does stuff heavy computational stuff, the barriers are quite low.

Now to figure out what to do with it...

Programming Shoot and Ladders

In college and highschool, we (really, the ubiquitous We, since i'd have this conversation with anyone who cared), spent a lot of time discussing the merits of different programming languages, about which model worked best and which was fastest for a given application. I spent a lot of time at work and home tinkering with different languages. Fortran, C, shell script (tcsh & pdksh), javascript/html, VB, perl, Igor, and labview.

However, I'm a career chemist, not a computer scientist. My goals are very much focused on cranking publications and not fine tuning code. I've come to realize the best tool for a lot of problem is the one you have to effectively solve the problem. One example: at work, one of our visualization products is written in Delphi. I doubt that would be the tool of choice for many people, but the scientist who is the PI knew pascal really well (back in the 1980s!) and it has stuck over time.

Of course, the tool you have works great, until you reach its limits. I use Labview for instrument automation. It has a easy to use GUI toolkit, and knows a lot about hardware and signals, right out of the box. Yesterday, I found something it doesn't know much about: drawing arbitrary graphics on screen.

 I'm building a control package for a vacuum manifold that preconcentrates gases before injecting them into a gas chromatograph. I thought it would be nice to give a visual representation of the flow paths that were open by drawing the manifold on screen. It turns out, labview doesn't give you many tools to do easily do that:

What this image is showing is that Labview's 2D drawing stack is entirely procedural, with no facilities for storing, moving, or transforming images after they've been created. Anytime your program wants to update an image screen, the code you write needs to explicitly redraw the entire image. It's not possible to algorithmically create a sprite library, then scoot the sprites around, or rotate or otherwise transform them. You have to build a bunch of routines that describe objects and then push those around.

Pain.

This means that it's going require writing quite a bit of code to make a panel that easily represent the open flowpaths to the user. Achieving that kind of functionality is not a high priority for the project, so for the time being, it will fall back on using more generic, less descriptive indicators.

If you're standing in front of the hardware, it's possible to guess what this means, but I think that's going to be beyond the grasp of inexperienced users, so I consider the solution to be suboptimal. Experience has shown that analytical error rates scale with the steps the analyst must complete and the clarity of state and hardware protection that software can provide. This panel doesn't clearly show linked flow paths, or if the instrument really knows if gases are moving or pressure tolerances are being exceeded.

Things could be a lot better.

Obey Posted Speed Limits

We took the Pike Peak Cog Railway to the top of Pikes Peak on Christmas Eve.

I think this is the first time in 10 years I've seen the trains up close (actually, it might be more, I don't remember if I drove up last time or took the Cog). This time I paid a lot more attention to the details of the engines.

The biggest gauge was the speedometer. It was about 8 inches in diameter and ranged from 0 to 15 mph. While slow compared to most commuter trains, I would note that most people can't climb the mountain that fast, and it can keep a decent speed up a grade at high altitude. My ponderings of higher velocities were curtailed when I looked out the window and saw this:

The rails are so warped that it would seem to be a mistake to attempt high speed travel. Besides, your sinuses might explode from the pressure change.

BlikenLichten

We bought timers for our Christmas lights this year. It let us have them on while we were away, and probably saved some money since we didn't forget and leave them on all night.

The timers we got are digital (I wanted grounded outlets, and digital was the only way we could find a time with grounded outlets.

Of course, we got it home and I had to take it apart; I had to know how it worked.

Do you recognize anything thing? Here, I'll give you a hint:

DC From AC Without a Transformer

The timer is made up of two boards, a power/switch board (left) and a clock board (right). The timer is powered by the rectifier/capacitor circuit in the lower left through the Yellow-Red wires, running to the clock. The clock has a battery (green, upper right), a photo sensor (middle far right, "dusk") and a quartz crystal (middle right). The clock signals a relay (black box, middle left) through a trigger circuit to turn the outlets on and off. I'm not precisely sure how that circuit works (didn't try to lift out that board). Plausibly, the clock opens the transistor (middle left, beside the relay), which applies partial rectified power using the diode and capacitor to the relay's coil. (The relay doesn't work when the timer is unplugged).

I'm surprised at how much of this timer is air and hand assembled discrete components.

Film Developing

If Wal-Mart charges $14 and refuses to give back your film, you should consider sending it to NCPS. NCPS does a great job developing film and also makes good quality scans. That's only ~$11 per roll.

Garden of the Gods

Over the holidays we visited my parents in Colorado. One of my favorite places near their house is Garden of the Gods. Although it was only early afternoon, the December sun was low enough that the light on the rocks was interesting and contrasting enough to help yield some interesting photos.

It reminds me of someplace Zane Grey would write about.

Where I Do My Work

I have to fill out lots of forms at work. I think somewhere there is someone whos job in our organization is to make forms, and that person is trying very hard to impress everyone with the quality and quantity of forms that must be filled out.

One of todays forms asked me to describe my home office. It is highly likely that the form was trying to determine if my work "environment" was a doghouse in the backyard. I wasn't sure, so I tried to cover as many bases as possible.

Describe your work environment:
"Small office with a door, a desk, rolling chair, and a telephone, and a north facing window looking out over a sizable bamboo stand, where raccoons and squirrels fidget. There is a grill in the floor that squirts hot air in the winter and cold air in the summer. The desk has two cups with miscellaneous writing instruments, a few scraps of paper, and a large computer monitor. There is also a small desklamp that makes very cool bright light. It makes me feel happy. The office also has shelves, a cubby closet, and a bureau for storing things. Beside the bureau is my treasured oscilloscope. It's analog, and thus doesn't face the nyquist sampling problems that digital scopes do, and it's green glow and soft waveforms are very nice.  There are several three pronged electrical outlets that supply electricity. Usually, I use that electricity for normal things, but sometimes I use it for unusual things. The door of the room is cheap and hollow, with white paint and a chrome brass knob. If I walk out the door and pull a hard right, I find myself in a bathroom, complete with running water, a commode, and a shower. The bathroom has not been cleaned in several weeks, but I will probably do it this weekend. If I forget to turn when I leave the office, I end up in the hall closet. It's dark in there."