• Polulu A4983 Stepper Motor Driver Carrier
• Makergear Plastruder Pack
• Kysan 42BYGH243AG14 Bipolar Stepper Motor
• John Yang’s PSCC V1.5 carrier board kit

I just finished soldering the carrier board kit with the shweet new Hakko 936 iron I got for Christmas.

We haven’t extruded any ABS plastic yet so you’ll have to settle for the impressive toothpick-and-electrical-tape indicator I stuck to the motor drive shaft :]

www.youtube.com/watch?v=ypC67-pY9AQ

Tips:

• Operating the PSCC V1.5 without its GND input connected will produce mysterious behavior (e.g. stepping the motor erratically based on the electrostatic fields of nearby objects!)
• The LED at top left indicates power supplied to the board.

Well too bad -- it’s just not possible to ascertain details that are hidden from the camera’s view!

You can get pretty close, though, with some software I discovered via an article in the Linux Journal.

GDV uses the Visualization Toolkit (VTK) to display what are called “surface plots”. I wanted to record a simple screencast of myself rotating a surface plot by hand but I couldn’t convince VTK to do “live” previews. As a workaround I whipped up this shell script which rotates the surface plot in small increments, taking screenshots along the way:

# simulate multiple click-and-drag mouse events along predetermined

# coordinates. after each of these click-and-drag events, take a screenshot
# with imagemagick's "import" utility.

# you should generate coordinates at which to click with...
#  (while :; do xdotool getmouselocation | \
#   awk '{print substr($1,3) " " substr($2,3)}'; done) | uniq
# ... and save them to the file at COORDS_PATH

# you can assemble the screenshots into a movie with...
#  ffmpeg -r 30 -b 300k -i %05d.jpg -b 1157kb out.mp4

COORDS_PATH=~/prog/sh/screenshot_rect_while_dragging.dat
SHOTS_DIR=/media/humid_data/tmp/shots
# head -n1 ${COORDS_PATH} | read PREV_X PREV_Y
# PUZZLE: why doesnt the above work? instead we'll use...
PREV_X=343; PREV_Y=135
I=1
mkdir ${SHOTS_DIR}
while read CUR_X CUR_Y
do
  echo moving to ${CUR_X} ${CUR_Y} as step ${I}
  # move to pos
  # greets to fellow RIT alum jordan sissel, xdotool's author
  xdotool mousemove ${PREV_X} ${PREV_Y}
  # mouse down
  xdotool mousedown 1
  # move to pos
  xdotool mousemove ${CUR_X} ${CUR_Y}
  # mouse up
  xdotool mouseup 1
  # give the app some time to finish rendering
  sleep .3s
  # take screenshot
  import -crop 640x480+38+130 -window root -quality 100 \
  ${SHOTS_DIR}/$(printf "%05d" ${I}).jpg

  I=$((I+1))
  PREV_X=${CUR_X}
  PREV_Y=${CUR_Y}
done < ${COORDS_PATH}

Next I assembled the screenshots into a video with Openshot, a young but very stable and featureful nonlinear video editor. Here’s the result:

www.youtube.com/watch?v=a4UCOrIZb2s

For some more image-processing fanciness, see this slick video demo of the “structural editing” tools planned for Photoshop CS5. There’s interesting discussion (incl. some NSFW comments) at this proggit thread. For instructions on feeding “heightmaps” to a 3D printer, see these instructions.

We stopped at the Museum of Science as soon as we arrived. It housed an excellent “history of mathematics” exhibit sponsored by IBM and sprinkled with comic strips to keep it from getting too heavy. I became comfortably lost there for almost an hour.

I stopped by the computing exhibit next and found a replica Enigma Machine -- a piece of WWII crypto history that was central to the plot of a book I just finished -- Neal Stephenson’s Cryptonomicon. The machine itself was understandably enclosed in a plastic display case, but an authentic Enigma transmission bleated out from a little speaker at the push of a button.

Around the corner I found “Whirlwind“, an early computer built down the river at MIT under an Air Force contract. The machine included a shoebox-size stack of “core” memory -- you know, the stuff made of ferrite donuts after which most Unixes name the memory dumps created for misbehaving programs¹. The museum installed a 16-bit bank of interactive core memory nearby that you can fiddle with . Dime-sized compasses indicate the values programmed at each bit. Neat.

www.youtube.com/watch?v=lnvWbq6V7AU

www.youtube.com/watch?v=K89lFWV2KcI

We consulted Yelp for dinner ideas and decided on Cafe Belo, a Brazilian BBQ restaurant in Everett of the rodizio style. You pay a fixed price ($10, there) and servers stop by your table every few minutes with hot meats on skewers, asking if you’d like a slice. Brazilian Beef ribs, Jamaican chicken, sirloin, pork, and some killer garlic beef.

On Saturday I got up early and took the train to Cambridge to visit the MIT campus.

It was quiet save for a scattered handful of undergrads with MIT sweatshirts looking more energetic than any undergrads I’ve seen on a weekend morning.

Access was restricted to Rivest‘s hallway, the Program Analysis Group‘s wing², and the Computer Systems Security Group‘s wing. I did, however, have lunch in the curiously-shaped Stata center and stumble across a Lisp Machine!

That afternoon we drove to the IMAX theater in Natick to see Tim Burton’s Alice in Wonderland. An enterprising furniture salesman convinced IMAX to build this theater in the middle of his showroom, thus guaranteeing a continuous flow of people in a receptive frame of mind. Ingenious.

On Saturday night we met Jumbo’s high school buddy, Mike, at his home a few blocks from Bunker Hill. We all went out to celebrate Mike’s birthday at the Midwest Grill. It turned out to be another Rodizio restaurant. In addition to Cafe Belo’s fare, we had bacon-wrapped chicken, sirloin tips, checken breasts, chicken hearts (!), and some of the best keilbasa I’ve ever had. The hot buffet included some amazing smooth and buttery ocra, two stews, and some mean pork rinds.

As if to prevent me from floating off into culinary heaven, our waitress denied my request for draft Sam Adams (imagine that -- out of Sam Adams in Boston) and instead brought me a bottle.

We returned around noon today after having some killer french toast at Ball Square Cafe in Everett and climbing the Bunker Hill Monument.

1. Linux 2.5+ gives you some options in this regard via its core_pattern `/proc` knob
2. Check out the deep reading list at the Program Analysis Reading Group’s site

Fortunately for us dub fans, Tabone has uploaded 87 of his hour-long shows in MP3 format with track listings. You can find them in the “Audio” section of the show’s website. Unfortunately, the recordings are only 16kbps. They sound a bit poor as you’d expect, but they only weigh in at around 7MiB apiece. I emailed Manwel to express my gratitude for his efforts and to ask about higher-quality recordings of his past shows. It turns out that none exist.

Most shows are a nice mix of roots reggae and dub. There are some dancehall tunes too. He’s even uploaded some tribute shows including a bunch with a Bob Marley theme.

I just got finished listening to show #674 which features “Finger on the Pulse” from The Dub Revolutionaries, a collaboration between Sly and Robbie and The Mad Professor. This track has a hot little sax line in it. So hot, in fact, that I had to go dig out my burned copy and listen to the whole thing!

www.youtube.com/watch?v=M9Wm8DHxW6I