Very direct look at USB 2 protocol with keyboard

Cool stuff. Digital storage oscilloscopes look to be very useful for looking at transmission data. I never got into that stuff, outside of learning fundamentals of reading logic gate and ic data (long forgotten now). Unfortunately the digital class I had never got into doing anything practical with any of it. It was a typical cram and test class. Any way, it’s amazing what can be done with on and off pulses.

Snookoda, did anything in particular get you interested in this video?

I have started reading Linux Device Drivers (3rd Edition) so am thinking about drivers, but it is just really interesting seeing the signal “live” on a piece of paper as it is in electrical form instead of abstracted away. Ben Eater’s videos are always entertaining, even though I’m mostly clueless about electronics. I can nod along but give me an empty breadboard and a stopwatch and I’d just have to nope out of there! :slight_smile:

Nice. That book looks like pretty hefty reading. A good book (or video series) on digital fundamentals (logic gates and higher level devices made up of them) might be very interesting to you. The topic starts with simple binary logic gates, simplifying progressively complex circuits of them using Boolean algebra (not nearly as scary as it might sound) and further into logic gate configurations of more complex logic ic’s for doing useful stuff, including memory, reading data from logic ic’s, and encoding and decoding fundamental protocols, which is very relevant to that USB video. The topic can be taught without any background in electronics. I had the class simultaneous with DC fundamentals and didn’t really need anything from the DC class to get on in the digital fundamentals class, since digital logic is abstracted away from the electronics level. But maybe that would be too long of a side topic from your current path (although very relevant and foundational).

I found that stuff fascinating in a class I had, despite the class itself being pretty mediocre. We didn’t do much of any hands on, 99% book work, and zero experimenting. Maybe one day I will find time to revisit that stuff.

I don’t understand the electrical current. What is it, and how can it transpose sound and vision? And then there’s the analog to digital thing… Where would be a good place to start? For the totally ignorant sucker.

Jorgen, the definition of current depends on who you ask. :grinning:

In typical academia, current is taught as flow of electrons (as if electrons are objects, or a quantity of them). So in this way of thinking, electrons (negatively charged) flow to a source of positive charge, which is called current. But even accepting this way of thinking about current, there is a big problem. At the engineering level, current has always been taught as flowing the wrong way, from positive to negative. And at the modern technician level, current is taught the right way, from negative to positive. In fact, markings on components, terminology, and schematic symbols were created long ago according to the wrong way of current flow. Academia refuses to change this, simply because of sticking to the past, avoiding having to modernize and explain a handful of wrong things in past engineering education (negative to positive is actually more intuitive too). Essentially, avoiding explaining that there was a simple mistake turned into a massive fuck up in physics many years ago and not admitting it by not correcting it.

Another way of thinking about current is as a sustaining of an electromagnetic field (not little symbolic particles called electrons) throughout a circuit which has a source of negative charge and positive charge attracting one another (like when you place two opposite magnet poles near each other, and this is very related), where it is said to have a direction of flow because of how the field behaves across some materials making up some electronic components.

Just to give you a simple example of the two current models here, the first says that current is a flow of electrons through a wire like water, where water analogies tend to break down miserably. The second says that current is a field around a wire, like the magnetic force between magnet poles, and this can actually be measured as such, which is why clamp-on current meters work.

I could get more into this if it is interesting to you, although not today. I do need to get some things done, including wiring up an a little Marshall type clone amp kit (and hope the damn thing works!).

The underlying mechanism of digital is voltage pulses being used to represent some data. For example, a pulse of 5 volts is an on state, and 0 volts is an off state. In binary math, it is 1 for on and 0 for off. All the complexity of digital is built upon that. And those on and off states are achieved using transistors as electrically controllable switches (essentially tiny and inexpensive relays), where a transistor has three legs. Two of the legs are essentially an open circuit, yet almost completed. The other leg sits between the two and allows for putting just enough voltage across the gap of the other two legs to initiate a complete path of current between the two. And removing the voltage of that middle leg drops the connection between those other two legs. Specific sequences of 1’s and 0’s are decided upon for representing some piece of information. For example, we could say that 1 = white and 0 = black for switching on and off a pixel. And the programming of such at the software level, using 1’s and 0’s to represent the on and off states at the hardware level, can be stored (as electrical charge!) and manipulated however a person likes. For example, we could say that if the mouse coordinate is at a specific location, switch a pixel state to ON to show the location of the mouse, and otherwise switch all pixels OFF to show where the mouse is not located.

This is also how a transistor used as a power amplifier works. Place a big current power source across the two legs (+ and ground), which have a very small gap between them preventing a completed circuit. Then on the third leg (sitting between + and ground legs of the transistor), input a small voltage signal (say a guitar signal), and the path will become completed via the introduced field from the small signal, where the current across the two legs will follow the shape of the smaller signal. So then what is happening with an amplifer is a big DC power source (DC here is a flat line graphed) is being modulated by the shape of the small voltage signal, and that big current pushes a speaker in and out according to the shape of the small signal. A small AC voltage signal controlling a big DC current source.

Take a look at this schematic symbol for a transistor.

B = base
C = collector
E = emitter

Notice the direction of the arrow, indicating that DC current flows from the collector to the emitter. See the problem there? Something that emits sends something, and something that collects receives something.

The collector would be connected to + of a DC power supply, and the emitter would be connected to - of the DC power supply (ground), and there is a very small gap between the two, preventing a completed circuit. Say the voltage difference between collector and emitter is 100 volts. A small voltage audio signal (say 1 volt) would be connected to base and ground, and as the small voltage signal rises on the base, an electric field is developed between the tiny gap between the emitter and collector and a current is initiated between them, following the rise and fall of the small voltage signal at the base. So a small 1 volt AC signal is controlling a 100 volts source that provides enough current to push the resistance of a speaker.

Another one, a diode.

The way that a diode works is that once a given voltage level is reached between the two legs (say 0.7 volts), current begins passing between the legs from negative to positive (a field develops over the gap), the flow being indicated by the big white arrow here. And if the diode were connected backward, current would not pass unless the voltage is VERY high, which is indicated by the straight line of the symbol (as if to block current), at which point the diode would breakdown. But there is again a problem here. The way that this device is actually connected to a supply voltage is opposite of what the symbol indicates, where negative is connected to the line side, and positive is connected to the arrow side, where current flows from the line side to the arrow side. The two small arrows here indicate that this is an LED type diode, emitting light. Some symbols for LED’s even have the little arrows pointing in the opposite direction, as if light is being received. But there are also light receiving devices with a similar symbol.

Lies, lies, everywhere. Even in science. :grinning:

@brainio: it seems quite chattily written as far as chattiness extends to Linux drivers, I need to compile a custom kernel to get going with the practical stuff and I don’t know yet if I’ll just stop when I have enough of an overview to know the unknown unknowns.

I know about logic gates inputs and expected outputs from using logical operators, it might be fun checking out the circuits and sticking some together on a breadboard. It must have been tough doing a course on this stuff with no experiments, sounds a bit dry!

Snookoda, studying on logic presented through digital electronics gives some stuff that I think isn’t learned through using logical operators in software programming, such as using Boolean algebra for simplifying numbers of logic gates (operators) down to simplest possible solutions for complex logic decisions, as one of the early things learned. I guess it’s hard to express how useful it all looked to be when it is all so faded away at this point. I don’t know why it is that logic approaches taught from both digital electronics and programming seem so different, because both seem like they would very useful across both. Programming approaches for arriving at fastest solutions. Digital electronics approaches making those solutions as efficient as they can be and seeing why many things in software are the way that they are. And I think those people who have learned both very well must have a superior understanding of how things work in computing devices.

The class I had was drier than a dead old lady’s vagina, taught by a first semester instructor who took the job because she (quoting her) “Honestly thought that teaching would be easy”, as she nearly had a breakdown mid-semester. She also often blurted out expressions such as, “God damnit!”, when things were falling apart. :joy: In her defense, she went above and beyond in trying to remedy a bad situation.

And the textbook had major and minor errors on every other page, including in end of chapter problem solutions, which made for a lot of unnecessary time untangling of this and that. It was a fucking nightmare but a damn interesting topic nonetheless. The director of the electronics department obviously didn’t review the books being used in the classes, and the students sure let him know about it.

Those could have been reasons why no time was reserved for hands-on and expriments.

Multiplexing and de-multiplexing was one particular interesting topic from that class. I don’t know if that is typically taught in programming.

And clocking.

There was a lot from that class that I wish I still had at least something of a grasp on.

If you ever jump into any of the electronics stuff, avoid at all costs textbooks written by Thomas L Floyd. I had to use a few of his books, which were all beyond horrible. One of my instructors refused to use the class textbook (by that same author), and put together something of his own book through a collection of resources that he had found and used over the years. That guy was a hell of an instructor, an old army guy.

Jeez, did she move to teaching statistics at a Scottish uni by any chance? :slight_smile: There might have been the usual hustle with the books just happening to be ones written by the faculty too!

I meant bitwise operators before, sorry - AFAIK it’s boolean algebra/turtles all the way down with and/or/not/xor. Clocking is something I want to know about, practical stuff like knowing when to stick capacitors and diodes inline with what and why.

Clocking is studied pretty well in Digital Fundamentals classes. Using components and non-logic silicon devices and doing the calculations are taught in analog AC classes, after DC. Component wise, DC is pretty much limited to resistors (and potentiometers), doing basic calculations for series and parallel, fundamental network analysis (using resistors), and some very limited use of capacitors and diodes. How I understand it, it used to be that power supplies were taught alongside DC, which changed over the decades, where many schools don’t even teach power supplies anymore outside of an engineering program. Seems stupid to me that it has been dropped because linear power supplies would be a great way to introduce differences between DC and AC, introducing diodes, capacitors, transformers, and efficiency of power supplies and why switching power supplies are used today.

I think the deal with how books are chosen is to do with deals (and probably kickbacks) between publishers and schools. And of course, books are updated every year, which is asinine. Fundamental electronics has been the same for over 100 years now. And digital fundamentals has been the same since back to the 80’s at least.

Lies and corruption, all the way down. :grinning:

Textbook publishers also resort to outright bribery, offering thousands of dollars in “reviewing” fees paid to profs who consider replacing their texts each year — profs also get taken on expensive junkets and wooed by publishers.

Goegan recently called out his school’s provost for allegedly forcing students to buy access codes, sending an email last month to the entire economics department that subsequently went viral. In the message, he claimed the provost there took a deal with Cengage. As InsideHigherEd reported, the gist of his accusation, which the college has categorically denied, is that, in return for a grant, the school compelled undergraduates to buy a $100 program called MindTap from the company, and also promised to fail at least 30 percent of students to somehow make it seem more effective.

“There were some semesters where I had over 1,000 students in my classes,” Goegan said. “With that many students, my choice of textbook would direct $100,000 to $200,000 in spending per semester. It’s no surprise that publishers will go to great lengths to get you to adopt their product.”

A good video going into some of the stuff brainio is talking about:

Does Electricity REALLY Flow? (Electrodynamics)

I’m thinking more along the line of both of these, not so much discrete particles and water flow analogy.

The electron field (19:40)

The skin effect in conductors

Thanks. I fear the theory is wasted on me, though. My mind isn’t fit for these things really. And I actually built a small electrical/electromagnetic motor in school when I was 15. Still got it somewhere. You hooked up a 9 volt battery and the thing started rotating at an impressive speed.

Thanks. I have this suspicion that nobody really knows what’s going on. It just works, and everybody is happy.