Reasonable expectation of privacy is the legal test, I think. The courts have ruled that in public, there is none. Chicago is the most over-surveilled city I could imagine. For probably fire or six years, there have been a huge number of CCTV cameras, mostly at intersections. In iffy neighborhoods, they are even in the middle of the block. They have large microwave link antennas, and can have a clear line of sight in four directions. If you look around a a square mile or so of hte city, you will see that they are all pointed at the closest precinct police station. They have ligt bars fomn police motorcycles on top of the (bulky) radio unit. A friend lives in a second floor apartment, and they put one of these outside his window.There are more cameras in lower-class neighborhoods, but they are everywhere. (Chicago is a patchwork of about 200 culturally and economically distinct neighborhoods). Mayor Daley several years ago mandated that any business open after midnight has to have cameras. Now the police department wants to use fresher technology to put covert cameras everywhere.
The cameras are clearly meant to intimidate. Daley is a man who's authority is not to be trifled with, and I cannot help but think that the embarrassment his father suffered from the 1968 police riot produced a "never again" mentality around dissent. Chicago has a long history of identifying and suppressing potential or perceived dissent. The infamous "red squads" ferreted out thought crimes until the feds ended the Chicago Police Department's Subversive Activities Unit in 1985.
Some things never change.
The cameras are clearly meant to intimidate. Daley is a man who's autority is not to be trifled with, and I cannot help but think that the embarressment his father suuered from the 1968 police riot has produced a:never again" mentality in his thinking. Chicago has a history of identifying and supressing dissent. The infamous "red squads" ferreted out thought crimes until the feds ended the Chicago Police Department's Subversive Activities Unit in 1985.
Most of what's being called serial here is asynchronous serial, meaning there's no external clock line. Each end of the connection has a clock that determines the baud rate, and so they must match in frequency within a couple of percent. There's a TX transmit line and an RX receive line and a ground wire in the minimal configuration. In a pc or an MCU there's a chip or an emulated version of same called a UART Universal Asynchronous Receiver Transmitter that takes care of buffering the serial bits as they come in (or go out of) the data wires One Bit At A Time. Many microcontrollers have built-in UART's. It used to be that the signal from a UART was universally converted to RS232 voltage levels. The spec says -12 volts is a 1 and +12volts is a 0. This is a really old standard that was invented to connect dumb terminals to mainframes through a modem. Several other wires are in the spec have to do with flow control and interacting with the modem. To get from 5 volt (or whatever) logic levels, a special line driver is used. A popular one is the MAX232 series of chips. These days the other lines in the RS232 cable are rarely used for their original purpose. The Arduino uses a flow control line to start the flash burner through a bootloader for instance. Async serial is very much still around because there are a large number of periperal chips and board-level modules that use a UART to communicate with an MCU or each other (sparkfun.com). In these applications, the voltage is at logic level. It is not shifted to RS232 levels, although you could do this if you needed to. The serial port on the original PC is a DB9 connector. The UART's interface to the CPU is interrupt driven, so you can do pretty good real-time stuff. Since the async serial port us pretty much gone on PC's, a lot of devices like most cell phone cables use an emulated UART port running over USB. There are a couple of companies that make USB to 5 or 3.3 volt UART converter chips that implement the USB protocol. Rather than having to put the USB protocol it in the target processor, you buy the functionality. Of course there are MCUs that know the USB stuff, but they're a bit uncommon. Also there's the whole licensing problem if you roll your own USB device. So as strange as it is, designing with an 8-bt MCU, you'll use a chip with a lot more horsepower than the target to handle the USB interface. This is a very, very common thing to do. The other half of the problem is the host device drivers. FTDI make chips with no-cost drivers that are routinely used alongside a lot of 8-bit MCUs. There are drivers in the linux kernel for a handful of converter chips, and FTDI's are the best known. The PITA for embedded designers is that the serial port emulated by the FTDI chip has buffering constraints and timing limitations (16ms latency) that basically ruin the real-time capability of the port. This really sucks. The alternative is to write your own drivers for Win, Mac, and Linux, and program your mcu to use one of the faster modes in the USB protocol than the one offered by the USB device class that includes async serial. For most people this doesn't matter. The host app on the PC uses its driver package that comes with, and you never have to know that your cell phone is using a 50 year old data link to talk to the pc.
The tools are beautiful objects, to be sure. But what makes beautiful science is elegant, concise, and simple (within the context) descriptions of how the universe works.
In the US we don't seem to have much interest in our technological past. These days we seem to value museum exhibits to the extent that we can "brand" them to advertise the donor corporation. This sale to corporations of cultural artifacts and institutions for use as vehicles for advertising is everywhere. Everything from art exhibits to sports arenas are defaced with logos. Twenty years ago the Museum of Science and Industry in Chicago had a really neat collection of IBM first-generation computing hardware on display. I went back later on to have another look and saw IBM desktop machines with peripherals and printouts in the display area with advertising on the wall behind. I was crushed. I asked the docent what happened to the display I had come to see. She told me that IBM wanted to get away from its image as a stodgy old company that built big impersonal machinery and that the historical display didn't fit their marketing efforts. So they traded up.
Britain on the other hand uses the lottery to fund preservation of its technological-cultural heritage. Another favorite of mine is the Kew Bridge Steam Museum. (q.v.)
Those of us who are Americans shouldn't lose sight of the fact that the culture that produced the contents of Bletchly and Kew is the culture that, in the late 18th and early 19th century, spread a temperament of tinkering, inventinting, hacking, making, and appropriating (and technological competition) across the Atlantic. I am an American, and a tinkerer in the best sense, and so this heritage is also mine. In the US we've lost so much of our past due to redevelopment, ignorance, and simple apathy that there's very little left to see, and what there is is often deteriorating (Henry Ford Museum - Greenfield Village, Eniac).
It is the responsibility of the State to preserve cultural history. You may think otherwise, but if you do, you're wrong. The simple reason is that our heritage is not yours to destroy by sins of omission. Our heritage belongs to our children. To claim that a heritage has no value because things that belong to everyone belong to no one and thereby implicitly demonstrate a lack of value, is to make a judgement based in a fad of popular culture (greed is good) that will evolve into some other way of thinking in the future. But by that time the damage done by neglect may be irrevocable.
If we are unwilling to do the work here, I sincerely hope that the Brits can find a way to do it there before their opportunity disappears, too.
The Baby is set apart from other early machines by two major features.
Memory was what we would call dynamic RAM. The storage element was special CRT's called Williams tubes which were the first all-electronic memory device (flip-flops we not economically viable for storing data). Williams tubes were randomly accessible and, used charges to store bits, and were therefore volatile. The volatile characteristic means that bits had to be refreshed by reading, or they would evaporate due to charge leakage. This is the same reason modern RAM chips have a periodic refresh cycle. This isn't a functional parallel, just a historically interesting one. FWIW, mercury delay lines are volatile, too, but not because of charge leakage. Programs were read into RAM from which they were executed.
The other feature of the Baby which was adopted into subsequent designs was conditional jumps - sort of like goto's. The relative jump is a jump to a calculated address. Without the ability to hop around the program space based on whether statements are evaluated as true or false precludes easy implementation of things like for loops and arrays. In 1998, the Z3 was mathematically proved to be capable of conditional jumps, but this was not an intent in its design and didn't lead anywhere.
The Baby had only seven instructions (take that, Microchip PIC!):
Jump (indirect), Jump Relative (indirect), Load Negative, Store Accumulator, Subtract, Skip if Accumulator < 0, Halt
A very good and hard to find page with info on the Mark I <URL:www4.wittenberg.edu/academics/mathcomp/bjsdir/madmmk1.shtml/>
I've had a Linux Fund card for a good while now. Clerks always say "awwwww what a cute penguin". But that's not why I got it. It was suppose to fund OS projects and encourage the health of the OS movement. Now that it looks like it won't be doing that, I think the best way to use the money to support OS is to ensure the legal right to tinker. OS is a subset of that genre of endevor, So I think the money should go to the EFF.
Getting motors and motor controllers with a high enough power density and acceleration (power) to move like that is pretty impressive. If you've never tried building a motion control system, the difficulty may not be apparent. There are multiple layers (or nested loops) of control at work here, and to get this fluidity of "organic motion" implies that in addition to the position, velocity, and acceleration control, they probably also have some rather sophisticated kinematic/inverse kinematic processing going on. This is not at all the same tech as a Robot Wars but-it-walks device would be.
I really wish I knew what kind of servo systems they're using and, even generally, what their control algo's look like. But that's probably a state secret.
Now Bush will give his buds at Enron or whoever carte blanche to screw everybody on their electric bills to "modernize the grid". I'm certain that the screwing will take place, but I bet the money from the increases never manages to show up as moderization. After all, who can say if they really do the work or not. Wink wink.
The only people who would want to know technical details like that would be the terrorists.
Multi-Channel motion control
on
Mirror, Mirror
·
· Score: 3, Informative
His system has one motor per "pixel". To produce the grey scale, he has to treat each pixel as an axis of position control. the two ways this is usually done is with servo's can do this with position feedback on the load (ala model-airplane servos), or with steppers which can be more finicky, but requre no feedback sensor. In either case, it wasn't trivial to build all the "pixels" and then get them under control. I'll bet it wasn't cheap either.
a recent experience with matrices
on
Pure Math, Pure Joy
·
· Score: 4, Insightful
I'd never studied linear algebra until recently when I had to learn just enough to work through the inverse kinematics of a robot arm. Actually, I never really got along with Mathematics very well anyway. But looking at how matrices can solve all kinds of problems just by drawing zig-zags through rows and columns of numbers made me wonder whether the problems they model or the problems themselves came first. As I was learning the little bit of this math that I did, it started to seem to me that the Math has an independent existence, and a somewhat mysterious set of relationships of correlations and causalities connected to but not dependant on physical nature.
Slashdot Mirror
Reasonable expectation of privacy is the legal test, I think. The courts have ruled that in public, there is none. Chicago is the most over-surveilled city I could imagine. For probably fire or six years, there have been a huge number of CCTV cameras, mostly at intersections. In iffy neighborhoods, they are even in the middle of the block. They have large microwave link antennas, and can have a clear line of sight in four directions. If you look around a a square mile or so of hte city, you will see that they are all pointed at the closest precinct police station. They have ligt bars fomn police motorcycles on top of the (bulky) radio unit. A friend lives in a second floor apartment, and they put one of these outside his window.There are more cameras in lower-class neighborhoods, but they are everywhere. (Chicago is a patchwork of about 200 culturally and economically distinct neighborhoods). Mayor Daley several years ago mandated that any business open after midnight has to have cameras. Now the police department wants to use fresher technology to put covert cameras everywhere.
The cameras are clearly meant to intimidate. Daley is a man who's authority is not to be trifled with, and I cannot help but think that the embarrassment his father suffered from the 1968 police riot produced a "never again" mentality around dissent. Chicago has a long history of identifying and suppressing potential or perceived dissent. The infamous "red squads" ferreted out thought crimes until the feds ended the Chicago Police Department's Subversive Activities Unit in 1985.
Some things never change.
The cameras are clearly meant to intimidate. Daley is a man who's autority is not to be trifled with, and I cannot help but think that the embarressment his father suuered from the 1968 police riot has produced a :never again" mentality in his thinking. Chicago has a history of identifying and supressing dissent. The infamous "red squads" ferreted out thought crimes until the feds ended the Chicago Police Department's Subversive Activities Unit in 1985.
Some things never change.
Most of what's being called serial here is asynchronous serial, meaning there's no external clock line. Each end of the connection has a clock that determines the baud rate, and so they must match in frequency within a couple of percent. There's a TX transmit line and an RX receive line and a ground wire in the minimal configuration. In a pc or an MCU there's a chip or an emulated version of same called a UART Universal Asynchronous Receiver Transmitter that takes care of buffering the serial bits as they come in (or go out of) the data wires One Bit At A Time. Many microcontrollers have built-in UART's. It used to be that the signal from a UART was universally converted to RS232 voltage levels. The spec says -12 volts is a 1 and +12volts is a 0. This is a really old standard that was invented to connect dumb terminals to mainframes through a modem. Several other wires are in the spec have to do with flow control and interacting with the modem. To get from 5 volt (or whatever) logic levels, a special line driver is used. A popular one is the MAX232 series of chips. These days the other lines in the RS232 cable are rarely used for their original purpose. The Arduino uses a flow control line to start the flash burner through a bootloader for instance. Async serial is very much still around because there are a large number of periperal chips and board-level modules that use a UART to communicate with an MCU or each other (sparkfun.com). In these applications, the voltage is at logic level. It is not shifted to RS232 levels, although you could do this if you needed to.
The serial port on the original PC is a DB9 connector. The UART's interface to the CPU is interrupt driven, so you can do pretty good real-time stuff. Since the async serial port us pretty much gone on PC's, a lot of devices like most cell phone cables use an emulated UART port running over USB. There are a couple of companies that make USB to 5 or 3.3 volt UART converter chips that implement the USB protocol. Rather than having to put the USB protocol it in the target processor, you buy the functionality. Of course there are MCUs that know the USB stuff, but they're a bit uncommon. Also there's the whole licensing problem if you roll your own USB device. So as strange as it is, designing with an 8-bt MCU, you'll use a chip with a lot more horsepower than the target to handle the USB interface. This is a very, very common thing to do. The other half of the problem is the host device drivers. FTDI make chips with no-cost drivers that are routinely used alongside a lot of 8-bit MCUs. There are drivers in the linux kernel for a handful of converter chips, and FTDI's are the best known.
The PITA for embedded designers is that the serial port emulated by the FTDI chip has buffering constraints and timing limitations (16ms latency) that basically ruin the real-time capability of the port. This really sucks. The alternative is to write your own drivers for Win, Mac, and Linux, and program your mcu to use one of the faster modes in the USB protocol than the one offered by the USB device class that includes async serial. For most people this doesn't matter. The host app on the PC uses its driver package that comes with, and you never have to know that your cell phone is using a 50 year old data link to talk to the pc.
The tools are beautiful objects, to be sure. But what makes beautiful science is elegant, concise, and simple (within the context) descriptions of how the universe works.
In the US we don't seem to have much interest in our technological past. These days we seem to value museum exhibits to the extent that we can "brand" them to advertise the donor corporation. This sale to corporations of cultural artifacts and institutions for use as vehicles for advertising is everywhere. Everything from art exhibits to sports arenas are defaced with logos. Twenty years ago the Museum of Science and Industry in Chicago had a really neat collection of IBM first-generation computing hardware on display. I went back later on to have another look and saw IBM desktop machines with peripherals and printouts in the display area with advertising on the wall behind. I was crushed. I asked the docent what happened to the display I had come to see. She told me that IBM wanted to get away from its image as a stodgy old company that built big impersonal machinery and that the historical display didn't fit their marketing efforts. So they traded up.
Britain on the other hand uses the lottery to fund preservation of its technological-cultural heritage. Another favorite of mine is the Kew Bridge Steam Museum. (q.v.)
Those of us who are Americans shouldn't lose sight of the fact that the culture that produced the contents of Bletchly and Kew is the culture that, in the late 18th and early 19th century, spread a temperament of tinkering, inventinting, hacking, making, and appropriating (and technological competition) across the Atlantic. I am an American, and a tinkerer in the best sense, and so this heritage is also mine. In the US we've lost so much of our past due to redevelopment, ignorance, and simple apathy that there's very little left to see, and what there is is often deteriorating (Henry Ford Museum - Greenfield Village, Eniac).
It is the responsibility of the State to preserve cultural history. You may think otherwise, but if you do, you're wrong. The simple reason is that our heritage is not yours to destroy by sins of omission. Our heritage belongs to our children. To claim that a heritage has no value because things that belong to everyone belong to no one and thereby implicitly demonstrate a lack of value, is to make a judgement based in a fad of popular culture (greed is good) that will evolve into some other way of thinking in the future. But by that time the damage done by neglect may be irrevocable.
If we are unwilling to do the work here, I sincerely hope that the Brits can find a way to do it there before their opportunity disappears, too.
The Baby is set apart from other early machines by two major features.
Memory was what we would call dynamic RAM. The storage element was special CRT's called Williams tubes which were the first all-electronic memory device (flip-flops we not economically viable for storing data). Williams tubes were randomly accessible and, used charges to store bits, and were therefore volatile. The volatile characteristic means that bits had to be refreshed by reading, or they would evaporate due to charge leakage. This is the same reason modern RAM chips have a periodic refresh cycle. This isn't a functional parallel, just a historically interesting one. FWIW, mercury delay lines are volatile, too, but not because of charge leakage. Programs were read into RAM from which they were executed.
The other feature of the Baby which was adopted into subsequent designs was conditional jumps - sort of like goto's. The relative jump is a jump to a calculated address. Without the ability to hop around the program space based on whether statements are evaluated as true or false precludes easy implementation of things like for loops and arrays. In 1998, the Z3 was mathematically proved to be capable of conditional jumps, but this was not an intent in its design and didn't lead anywhere.
The Baby had only seven instructions (take that, Microchip PIC!):
Jump (indirect), Jump Relative (indirect), Load Negative, Store Accumulator, Subtract, Skip if Accumulator < 0, Halt
A very good and hard to find page with info on the Mark I <URL:www4.wittenberg.edu/academics/mathcomp/bjsdir/madmmk1.shtml/>
I've had a Linux Fund card for a good while now. Clerks always say "awwwww what a cute penguin". But that's not why I got it. It was suppose to fund OS projects and encourage the health of the OS movement. Now that it looks like it won't be doing that, I think the best way to use the money to support OS is to ensure the legal right to tinker. OS is a subset of that genre of endevor, So I think the money should go to the EFF.
Getting motors and motor controllers with a high enough power density and acceleration (power) to move like that is pretty impressive. If you've never tried building a motion control system, the difficulty may not be apparent. There are multiple layers (or nested loops) of control at work here, and to get this fluidity of "organic motion" implies that in addition to the position, velocity, and acceleration control, they probably also have some rather sophisticated kinematic/inverse kinematic processing going on. This is not at all the same tech as a Robot Wars but-it-walks device would be.
I really wish I knew what kind of servo systems they're using and, even generally, what their control algo's look like. But that's probably a state secret.
Now Bush will give his buds at Enron or whoever carte blanche to screw everybody on their electric bills to "modernize the grid". I'm certain that the screwing will take place, but I bet the money from the increases never manages to show up as moderization. After all, who can say if they really do the work or not. Wink wink.
The only people who would want to know technical details like that would be the terrorists.
His system has one motor per "pixel". To produce the grey scale, he has to treat each pixel as an axis of position control. the two ways this is usually done is with servo's can do this with position feedback on the load (ala model-airplane servos), or with steppers which can be more finicky, but requre no feedback sensor. In either case, it wasn't trivial to build all the "pixels" and then get them under control. I'll bet it wasn't cheap either.
I'd never studied linear algebra until recently when I had to learn just enough to work through the inverse kinematics of a robot arm. Actually, I never really got along with Mathematics very well anyway. But looking at how matrices can solve all kinds of problems just by drawing zig-zags through rows and columns of numbers made me wonder whether the problems they model or the problems themselves came first. As I was learning the little bit of this math that I did, it started to seem to me that the Math has an independent existence, and a somewhat mysterious set of relationships of correlations and causalities connected to but not dependant on physical nature.