I wanted a partition to divide my room, and I had a whiteboard sitting around. I sawed it into three parts, and connected them with hinges:
I’m a little embarrassed at having done all this, since it was obvious as soon as I started the partition was way too short to work. I figured I’d still get some experience woodworking (this is my first project). Here’s where it went:
and I never saw it again
Recipe is mostly from Tricia.
Ingredients:
Read about raw beef and egg safety first to be well informed.
Previous work:
I wanted (for fun) to see if I could get data stored in paper formats. I’d read the previous work, and people put a lot of thought into density, but not a lot of thought into ease of retreival. First off, acid-free paper lasts 500 years or so, which is plenty long enough compared to any environmental stresses (moisture, etc) I expect on any paper I have.
Optar gets a density of 200kB / A4 page. By default, it requires a 600dpi printer, and a 600+dpi scanner. It has 3-of-12 bit redundancy using Golay codes, and spaces out the bits in an okay fashion.
Paperback gets a (theoretical) density of 500kB / A4 page. It needs a 600dpi printer, and a ~900dpi scanner. It has configurable redundancy using Reed-Solomon codes. It looks completely unusable in practice (alignment issues, aside from being Windows-only).
Okay, so I think these are all stupid, because you need some custom software to decode them, which in any case where you’re decoding data stored on paper you probably don’t have that. I want to use standard barcodes, even if they’re going to be lower density. Let’s look at our options. I’m going to skip linear barcodes (low-density) and color barcodes (printing in color is expensive). Since we need space between symbols, we want to pick the biggest versions of each code we can. For one, whitespace around codes is going to dominate actual code density for layout efficiency, and larger symbols are usually more dense. For another thing, we want to scan as few symbols as possible if we’re doing them one at a time.
Aztec From 15×15 to 151×151 square pixels. 1914 bytes maximum. Configurable Reed-Solomon error correction.
Density: 11.9 pixels per byte
Data Matrix From 10×10 to 144×144 square pixels. 1555 bytes maximum. Large, non-configurable error correction.
Density: 13.3 pixels per byte
QR Code From 21×21 to 177×177 square pixels. 2,953 bytes maximum. Somewhat configurable Reed-Solomon error correction.
Density: 10.6 pixels per byte
PDF417 17 height by 90-583 width. 1100 bytes maximum. Configurable Reed-Solomon error correction. PDF417 is a stacked linear barcode, and can be scanned by much simpler scanners instead of cameras. It also has built in cross-symbol linking (MacroPDF417), meaning you can scan a sequence of codes before getting output–handy for getting software to automatically link all the codes on a page.
Density: 9.01 pixels per byte
QR codes and PDF417 look like our contenders. PDF417 turns out to not scan well (at all, but especially at large symbol sizes), so despite some nice features let’s pick QR codes. Back when I worked on a digital library I made a component to generate QR codes on the fly, and I know how to scan them on my phone and webcam already from that, so it would be pretty easy to use them.
What density can we get on a sheet of A4 paper (8.25 in × 11.00 in, or 7.75in x 10.50in with half-inch margins)? I trust optar’s estimate (600 dpi = 200 pixels per inch) for printed/scanned pages since they seemed to test things. A max-size QR code is 144×144 pixels, or 0.72 x 0.72 inches at maximum density. We can fit 10 x 14 = 140 QR codes with maximum density on the page, less if we want decent spacing. That’s 140 QR codes x (2,953 bytes per QR code) = 413420 bytes = 413K per page before error correction.
That’s totally comparable to the other approaches above, and you can read the results with off-the-shelf software. Bam.
In a previous post I discussed how to backup android with rsync. In this post, I’ll improve on that solution so it happens when you plug the phone in, rather than manually. My solution happens to know I have only one phone; you should adjust accordingly.
The process is
First, let’s add a udev rule to auto-mount the phone when it’s plugged in and unlocked, and run appropriate scripts.
# 10-android.rules
ACTION=="add", SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee2", MODE="0660", GROUP="plugdev", SYMLINK+="android", RUN+="/usr/local/bin/android-connected"
ACTION=="remove", SUBSYSTEM=="usb", ENV{ID_MODEL}=="Nexus_4", RUN+="/usr/local/bin/android-disconnected"
Next, we’ll add android-connected and android-disconnected
#!/bin/bash
# /usr/local/bin/android-connected
if [[ "$1" != "-f" ]]
then
echo "/usr/local/bin/android-connected -f" | /usr/bin/at now
exit 0
fi
sudo -u zachary DISPLAY=:0 /usr/bin/notify-send "Android plugged in, please unlock."
sudo -u zachary /usr/local/bin/android-mountfs
sudo -u zachary DISPLAY=:0 /usr/bin/notify-send "Mounted, backing up..."
/usr/bin/flock /var/lock/phone-backup.pid sudo -u zachary /usr/local/bin/phone-backup-xenu
sudo -u zachary DISPLAY=:0 /usr/bin/notify-send "Backup completed."
# !/bin/sh
# /usr/local/bin/android-disconnected
#!/bin/sh
sudo -u zachary DISPLAY=:0 /usr/bin/notify-send "Android unplugged."
sudo -u zachary /usr/local/bin/android-umountfs
We’ll add something to mount and unmount the system. Keeping in mind that mounting only works when the screen is unlocked we’ll put that in a loop that checks if the mount worked:
#!/bin/sh
# /usr/local/bin/android-mountfs
android_locked()
{
ls /media/android 2>/dev/null >/dev/null
[ "$?" -eq 2 ]
}
jmtpfs /media/android # mount
while android_locked; do
fusermount -u /media/android
sleep 3
jmtpfs /media/android # mount
done
#!/bin/sh
# /usr/local/bin/android-umountfs
fusermount -u /media/android
The contents of /usr/local/bin/phone-backup are pretty me-specific so I’ll omit it, but it copies /media/android over to a server. (fun detail: MTP doesn’t show all information even on a rooted phone, so there’s more work to do)
Compared with last update, the Dead Tree Publishing website is looking nicer.
It’s served over HTTPS now (not needed for security, but it puts people at ease and enabled Chrome’s autocomplete) and you can order multiple books at a time.
Other than some more visual improvements, the main thing missing is proper detection of page size — my server doesn’t understand about page margins, so it things books are bigger than they really are.
Most of the following taken from : http://www.msfn.org/board/topic/151992-install-xp-from-usb-without-extra-tools/, just modified to include syslinux support.
Let me know if there are any omissions; it an XP installer bluescreens on boot for me so I can’t actually test.
syslinux -i /dev/sdXX
$ cp /usr/lib/syslinux/bios/mbr.bin >/dev/sdX
$ mount /dev/sdXX /mnt
mkdir /tmp/xp_iso
mount xp.iso /tmp/xp_iso
cp -ar /tmp/xp_iso/* /mnt
umount /tmp/xp_iso
rmdir xp_iso
cp /usr/lib/syslinux/bios/{chain.c32,libutil.c32,menu.c32,libcom.c32} /mnt
cp /mnt/I386/{NTDETECT.COM,SETUPLDR.BIN,TXTSETUP.SIF} /mnt
Edit /mnt/syslinux.cfg:
UI menu.c32# Windows XP
LABEL windows_xp
MENU LABEL Run Windows ^XP Setup
COM32 chain.c32
APPEND fs ntldr=SETUPLDR.BIN
umount /mnt
Boot from the USB stick
Last post I discussed the publishing website I’m working on.
Today I added credit card processing and address forms–it’s functionally complete and available at https://publishing.za3k.com
Next up I have to clean the site up, because it looks like this:
I’ll also add HTTPS.
I started work on my publishing website again (Dead Tree Publishing). The idea is to make a really, really convenient way to get a physical copy of a PDF/epub book. Think: “send me a printed copy of this mailing list / tumblr”. Right now things are looking encouraging.
I use a “back end” publisher who does all the actual printing, and the one I was using before charged quite a lot and wasn’t amazingly fast; I just used them because they were the only publisher who was at all up to date. Seriously, order of $100 – $200 for a 100 page book, just absolutely ridiculous levels of expensive. I’m switching over to a new publisher who can offer that same book for something like $7 (maybe $12 in hardback), which is absolutely reasonable, and with similar 2-week turnaround times.
First you upload a PDF:
Then I tell you what your ordering options are (hardcover, softcover, color), and what they cost. I’m also supposed to ask you your address to ship the book, and for you to pay for it, but those aren’t done yet.
Hopefully in the next day or two I’ll have something up and running so people can order books, and then make it gradually nicer! I’m very excited about this website existing.
Just a quick shout-out to Chrome extension Stylish, which lets you add custom stylesheets to any web page. I’m using it with “display: none” and “visibility: hidden” exclusively, to hide annoying page elements.
I wrote a list of video games which I’ve enjoyed especially here.