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http://en.wikibooks.org/wiki/Serial_Programming/8250_UART_Pr...
Had to look it up, my brain was coming up with Logical Shift Right.
780 karma · joined January 18, 2012
> Inside the building, on those top floors, the oscillation is what unnerves us. A forty-story building may sway a foot to the left, a foot to the right. The span of that period might last around four seconds. A hundred-story building, by comparison, may move on the order of two-and-a-half to three feet to each side, cycling through a ten-second period. Typically, the taller the building, the longer the period of its cyclical motion.
And the implicit question of how much movement we feel:
> Acceleration is what causes the body forces that might tip us off our firmly planted feet, or nudge us back into the passenger seat of a car pulling away from a stoplight. Fighter pilots experience acceleration at many times the magnitude of gravity—“4 Gs” or more. The top of our hundred-story skyscraper accelerates through its period, as it sways from one side to the other, at a mere fraction of what a fighter pilot feels: maybe ten milli-g’s, or one hundredth of the force of gravity.
RPi is closer to a vanilla laptop/PC than it is to an Arduino.
Arduino describes an ecosystem of microcontrollers, traditionally 8-bit AVR and more recently 32-bit ARM. Microcontrollers are designed specifically (physically, instruction set, cost) to control low-level digital and analog IO, and not to run a general Operating System.
Raspberry Pi etc are general purpose computers. They only differ from your general laptop etc in form factor, and that they're built around a System on a Chip (SoC) rather than discrete CPU and peripherals. In that regard it's much like your cell phone, tablet, Chromebook and other budget laptop/desktop computers. But general computers are moving in that direction too — on-chip graphics, ethernet etc. Because RPi targets education and hobbyists, its form factor exposes some general purpose IO (GPIO) pins, much like a general computer parallel port might.
As far as I know, Raspberry Pi doesn't have ADC on-board, but you can wire an external one into its digital GPIO/SPI pins. You could also plug a USB or serial port ADC into your laptop, or your RPi.
With regard to “physical computing”, there's generally a real-time requirement, which cannot be achieved with a multi-tasking OS. Microcontrollers generally run at less then 100 MHz (often 8 or 16 MHz), but because of their instruction set design, timer and interrupt systems, and lack of multitasking, they can reliably and rapidly sample inputs or trigger outputs. A 48 MHz microcontroller could perhaps come close to 1 MHz sample rate.
SoC devices and general purpose computers are designed to run a multi-tasking OS at GHz speed with heaps of RAM. But despite that, this example shows an inability to reliably control I/O at more than 100 KHz when running a general (multitasking) OS. IO tasks that do require real-time characteristics (USB, ethernet, etc) are delegated to separate controller chips.
It's possible to write “bare-metal” code to run directly on a Raspberry Pi (or any computer) without an operating system which brings it closer to behaving like a microcontroller, but the instruction set isn't optimized for this, nor are the compilers/toolchains, and nor is the I/O and on-chip peripherals of the SoC.
Hope that meandering ramble helps.
— https://web.archive.org/web/20110521104819/http://www.apple.... via http://apple.stackexchange.com/a/12280
This could also be useful, but doesn't answer the question directly: http://www.apple.com/batteries/maximizing-performance/
Schneier on Security — Hacking Computers Over USB https://www.schneier.com/blog/archives/2006/06/hacking_compu...
The block-quote incorrectly mentions DMA over USB, but the described attack uses Windows AutoRun. The comments discuss a demonstrated FireWire iPod based DMA attack, and that USB doesn't expose DMA.
USB doesn't exposes DMA.
“Examples of connections that may allow DMA in some exploitable form include FireWire, ExpressCard, Thunderbolt, PCI and PCI Express.” – http://en.wikipedia.org/wiki/DMA_attack
The scenario described happens frequently when people `git push -f` a rebased tree, and it certainly does not go unnoticed by other developers on the project — more “havoc” than “subtle”.
and…
> It’s the same as firearms, if local P.D or Highway Patrol were to pull someone over that is a registered firearm owner, that officer has the right to know this information going into the interaction, the same could be said about a local P.D or Highway Patrol Officer that pulled over a registered motorcycle owner, the situations are honestly interchangeable in the eyes of National and Homeland Security.
Disturbing.
Edit: you could say “record the error and give the option to report it” but that's a whole lot of extra complexity, both UI and code. Especially for a bunches of single-purpose composable tools.
Has that ever happened on MacBook? It seems that better hardware and software, Apple has completely eliminated that issue.
Meanwhile, Arduino SRL (I can't help but think of them as “the fake Arduino”) have announced their Arduino Zero Pro[1] which appears to be the same thing, and is apparently available now.
However, the Zero Pro doesn't seem to be available through any reputable outlets (yet?). Perhaps the SRL lacks the distribution network / credibility of the LLC?
[0]: http://arduino.cc/en/Main/ArduinoBoardZero [1]: http://arduino.org/products/arduino-zero-pro
The TP3465 SPI chip mentioned sounds useful — I've been building a single-board 6502 which is CPU bit-banging SPI at 1 MHz, and takes about a minute to fill a small 16-bit color screen. I've wanted to offload that to an SPI chip, but hadn't found any. The downside; the TP3465 chips are about $11 each on Mouser, and don't come in hand-solder-friendly packages.
I mostly came here to write that I'm puzzled by “reasons I shouldn’t need to explain” here, though:
> In terms of disclosure of what is inside this CPLD – [...] Its final design is now almost entirely VHDL. If there’s sufficient interest I’ll do a good diagram of it at some point, but for reasons I shouldn’t need to explain, I won’t be providing the full source for it just yet.
I could only guess, from most to least likely; (a) it contains proprietary IP that is being used without a license, (b) he considers it too messy to release, (c) he just doesn't want to, or (c) he wants to retain the ability to license his creation.
“For years, I used to run Debian sid (unstable) on all my personal machines.”
“Sometimes things broke. But it wasn’t a big deal, because I could always get in there and fix it fairly quickly, whatever it was.”
“I’ve googled this issue, and found all sorts of answers pointing to polkit, or dbus, or systemd-shim, or cgmanager, or lightdm, or XFCE, or… I found a bug report of this exact problem — Debian #760281, but it’s marked fixed, and nobody replied to my comment that I’m still seeing it.”
… doesn't sound like somebody “who forget the beginner's spirit to look for answers on forums [etc]”
followed immediately by this inline ad:
> Try Newsweek for only $1.25 per week
… deliberate or accidental irony?
> The light emitted by most e-readers is shining directly into the eyes of the reader, whereas from a printed book or the original Kindle, the reader is only exposed to reflected light from the pages of the book.
So it's talking entirely about brightly backlit tablets, not e-readers with e-ink.
It was 1997. I'm pretty sure software and firmware was already in almost every device we own. But it's probably true that lawmakers had no idea.
Looks like a normally proportioned guy to me.
> Why is the project named Bitrig? > > The name Bitrig is derived from the Latin "Bitrigus", the name of the software used by the Romans to conquer Europe. Sadly, not having zero among its numerals made traditional computer science difficult for the Romans and the project was put on hold indefinitely. Bitrigus faded into obscurity until it was recently rediscovered at a Viking archaeological site in the modern day country of Iceland. > > The Roman emperor Hadrian is rumored to have sent Bitrigus as far west as a boat could carry it to keep it from the then growing threat of religious fanaticism within the Roman Empire.