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Using large format paper with Linux and the Epson WorkForce WF-7520 printer
Update: Nope, I can’t get this to work any more.
I have an Epson WorkForce WF-7520, and I really like it: excellent built-in duplex large format scanner with ADF, CIFS network storage, giant paper bins, photo quality printing up to 330×482 mm, only slightly expensive print cartridges… Under Linux, though, it’s not so well behaved, especially if you want to print on large format paper. This is the workaround I developed:
- Put the B-size/11×17″ paper in Tray 1 (the upper one), and the Letter paper in Tray 2. This, unfortunately, matters — the driver that can print large format can only access the upper tray. On the setup menu on the printer console, tell the printer which tray holds what size of paper.
- Install the epson-inkjet-printer-escpr driver; it should be in the standard Ubuntu repos. Define a printer (wf7520-lf, for example) that uses this driver. Set the paper size to “US B 11 x 17 in”.
- Ensure that the lsb and lsb-printing packages are installed:
sudo apt-get install lsb lsb-printing - Download and install the non-free epson-201115w driver from the EPSON Download Center. Define a printer (I used wf-7520 for the name) using this driver, making sure that the correct PPD (epson-inkjet-printer 1.0.0-1lsb3.2 (Seiko Epson Corporation LSB 3.2)) is used. Set it up to use Letter paper, and (important!) set the source to Paper Cassette 2. You might want to make this printer the system default.
To print to large format, use the command:
lp -d wf7520-lf -o PageSize=USB file.pdf
To print regular size, just send the job to the wf-7520 device.
(modified from my Ask Ubuntu question/answer: Selecting Large Format Paper: what printing options work?)
Update for the (rightly) confused: Epson appear to have hoiked US B / 11×17″ support for this printer. Here are my PPDs:
- Epson-WF-7520_Series-epson-driver.ppd — this is from the non-free driver. It doesn’t need to support large format.
- wf7520-lf.ppd — this is the large-format driver I use. Compare it with the epson-inkjet-printer-escpr PPD in the Debian code repo, and you’ll find all references to many paper sizes gone from it. Hmm …
Copying PPDs from one driver to another may not work, but you’ve likely nothing to lose.
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ZX Spectrum → Canada
Ah, the ZX Spectrum… so many hours of my youth wasted on this book-sized computer. Now anything with a display can emulate one in its spare processor cycles, the 30 year old hardware itself is a bit chunky:
That’s a lot of discrete components; all through-hole, too. I brought this one back from the UK earlier this year in the hope of getting it working.First item that needed attention was the power supply. The original had a 230 V AC to 9 V DC, 1.4 A supply of some extremely dodgy regulation. I replace this with a Circuit-Test AC/DC Adapter – 9 V DC 2.2 A, which will have plenty of current. Since the adapter has a 2.1 mm centre positive DC barrel connector, and the Spectrum uses a centre negative connector, I used the soldering opportunity to wire in an inline switch. The Speccy’s famous lack of a power or reset switch really isn’t part of my retrocomputing experience.
Next up, bypass the UK PAL TV modulator. This required disassembling the computer, and disconnecting the legendarily fragile keyboard membrane edge connectors. It’s a very simple soldering job to re-route the composite video feed (dot crawl and all) from the PCB to the Video Out. Put it all back together, plug it into the TV, and:
… another partial success. My TV doesn’t talk 50 Hz PAL composite well, giving an oversized black and white display. I’ll either need to buy a PAL to NTSC converter box, or spring for a tiny monitor which supports both standards.
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And this, kids, is why we rig our dipoles with black Dacron …
I guess the “UV Resistant!” nylon rope I used to rig my mini-G5RV wasn’t that resistant. Two summers of Scarborough sun did for it, turning the casing into friable dust. I knew that buying that big reel of black antenna rope last year was a good idea. -
Artisanal Hardware Random Number Generator
Artisanal Hardware Random Number Generator — scruss
(the Flickr page has popup notes about the circuit.)Trickles out a few thousand made-with-love organic random numbers per second to the attached Arduino. The circuit is essentially Rob Seward’s True Random Number Generator v1 (after Will Ware, et al) which uses a MAX232 to power two reverse-biased 2N3904s to create avalanche noise. Another 2N3904 amplifies the resulting noise into something an Arduino can sample using AnalogRead(). Many modern processors include hardware RNGs (such as RdRand in recent Intel chipsets) so this circuit is just a toy now.
My interest in random number generators didn’t just arise from yesterday’s post. I’ve had various circuits breadboarded for months gathering dust, so I thought I’d pull out the most successful one and photograph it. Hardware RNGs seem to be a popular hobby electronics obsession, and there are many designs out there in variable states of “working†and/or “documentedâ€. I wanted one that could be powered from the 5V rail of an Arduino, and didn’t use too many expensive components. Rob’s RNG Version 2 circuit and code is the basis, but I replaced the 12V external supply with the MAX232 circuit he used in version 1.
Perhaps the reason that there are so many RNG projects out there in various states of abandonment is that making a good, reliable hardware RNG is hard. Just a few of the things you have to think about are:
- Analogue sources of noise can fade over time; power supplies droop as capacitors age, contacts can corrode, … How do you deal with this fade? If the output becomes so small, can you rely on those few bits from your A→D converter to be useful noise?
- Could someone try to attack your RNG so they can influence the results of your secure transactions? How would you detect it? How would you signal to the data user that something is amiss securely, such that an attacker couldn’t fake distress behaviour?
- What if the generator just stops? How do you flag that in a trusted “no really i mean it and it’s really me saying this not some attacker honest no†way? There may still be a tiny bit of noise that your circuit picks up; are you sure it’s your kind of noise, or some attacker trying to inject noise into your system? Remember, testing for real noise is exceptionally hard, and you can’t guarantee that a hardware RNG that worked today will work properly tomorrow.
(I’d like to thank Peter Todd for providing most of those issues over a pint and a chat during from a keysigning event. Peter saved me from spending too many hours working on this by hinting that — just maybe — I didn’t actually know what I was doing…)
If you want to read more on how to build a proper hardware RNG, the article “Understanding Intel’s Ivy Bridge Random Number Generator†and its references make a good (if very technical in places) introduction. I’m nowhere near paranoid enough to experiment further with RNG design, although I do have all the components to build an LM393-based XR232USB…
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“Well, that was unexpected …”: The Raspberry Pi’s Hardware Random Number Generator
Hey! This is a bit old! Things may have changed and I haven’t necessarily fixed them.
Most computers can’t create true random numbers. They use a formula which makes a very long stream of pseudo-random numbers, but real randomness comes from thermal noise in analogue components. The Raspberry Pi has such a circuit in its SoC, as it helps making the seed data for secure transactions. It was only recently that a driver for this circuit was supplied.
To enable it (on Raspbian):I think the module is enabled by default now for the different versions of the SoC.- Make sure your system is up to date with
sudo apt-get update
sudo apt -y upgrade Install the module:sudo modprobe bcm2708-rngTo make sure it’s always loaded, add the following line to /etc/modules (editing as root):bcm2708-rng- For some RNG-related stuff, install rng-tools:
sudo apt-get install rng-tools
The /dev/hwrng device should now be available, but can only be read by the root user.
Nico pointed out that you also need to:
- Edit /etc/default/rng-tools, and remove the # at the start of the line
HRNGDEVICE=/dev/hwrng - Restart rng-tools with
sudo service rng-tools restart
What random looks like
Random data look pretty dull. Here are random RGB values made with:
sudo cat /dev/hwrng | rawtoppm -rgb 256 256 | pnmtopng > random$(date +%Y%m%d%H%M%S).png(you’ll need to install the netpbm toolkit to do this.)
What random sounds like
Two short WAV samples of, well, noise:
Yup, sounds like static. It was made with the rndsound.sh script. You’ll need to install sox to run it.
This is not random
If it sounds like static, and even if it sometimes looks like static, it may not actually be true random noise. An infamous case of a pseudo random number generator being not very random at all was RANDU, which at first glance appeared to produce nearly random results, but close study showed it to be very predictable.
I wrote (what I think to be) a C implementation of RANDU: randu.c. While it produces appropriately random-sounding audio data (randu17.wav), if you output it as an image:
Those stripes are a giveaway; there should be no order in the output. (Then again, I have no idea if I’ve implemented RANDU correctly.) Testing random data is hard, then — you really need a barrage of tests, and even some of them might fail even for truly random output. Thankfully, when you installed rngtools, it included rngtest, a simple checker for random data:sudo cat /dev/hwrng | rngtest -c 1000
rngtest 2-unofficial-mt.14
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.rngtest: starting FIPS tests…
rngtest: bits received from input: 20000032
rngtest: FIPS 140-2 successes: 1000
rngtest: FIPS 140-2 failures: 0
rngtest: FIPS 140-2(2001-10-10) Monobit: 0
rngtest: FIPS 140-2(2001-10-10) Poker: 0
rngtest: FIPS 140-2(2001-10-10) Runs: 0
rngtest: FIPS 140-2(2001-10-10) Long run: 0
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=67.969; avg=921.967; max=1953125.000)Kibits/s
rngtest: FIPS tests speed: (min=842.881; avg=3208.336; max=6407.890)Kibits/s
rngtest: Program run time: 27658884 microsecondsWe were lucky that none of the tests failed for that run; sometimes there are a few failures. RANDU, on the other hand fares very badly:
./randu 17 | rngtest -c 1000
rngtest 2-unofficial-mt.14
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.rngtest: starting FIPS tests…
rngtest: bits received from input: 20000032
rngtest: FIPS 140-2 successes: 0
rngtest: FIPS 140-2 failures: 1000
rngtest: FIPS 140-2(2001-10-10) Monobit: 730
rngtest: FIPS 140-2(2001-10-10) Poker: 1000
rngtest: FIPS 140-2(2001-10-10) Runs: 289
rngtest: FIPS 140-2(2001-10-10) Long run: 0
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=45.630; avg=14255.221; max=19073.486)Mibits/s
rngtest: FIPS tests speed: (min=23.694; avg=154.238; max=176.606)Mibits/s
rngtest: Program run time: 141071 microsecondsSee? Lots of failures there. It’s hardly random at all. If you really want to get out testing randomness, there are the dieharder tests. They takes ages to run, though.
(Note: newish Intel machines also have a real hardware RNG in the shape of Rdrand.)
I trust you all got the obvious Strictly Ballroom reference in the title?
- Make sure your system is up to date with
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Like I need /more/ pens…
Uhoh. Wonder Pens sells pens — neato pens — and they are in Toronto. The Platinum Preppy they sent me free with my first order writes better than any $4 fountain pen should.
