Tue Feb 21 16:56:18 UTC 2023 /nisanth/notes.d/stm32f4x.d/stm32f4xx_saga-pt-I.01.txt Saga text here ;) TODO Ideas Ideas formed during this document's creation on Tuesday 21 Feb 2023: Tue Feb 21 17:37:29 UTC 2023 idea: gpio pin made of PN2222A and its symmetrical mate, only, as the primary technology. Not sure what that circuit'd look like or if it needs a clock (think it does). Tue Feb 21 17:37:29 UTC 2023 SOMEWHERE close to 1970, I saw a good-sized cut piece of plywood. We had built (or at least vistited) other tree-forts made of the same (or similar) manufactured wooden material. It's strong. The plywood had, mounted on it: a telephone rotary dial; several 6.3 Volt incandescent (bayonet base) light bulbs, and I don't know know just what else. No memory of how it came to be shown to me. To demonstrate, that person put their finger into the dial and dialed a number, as usual. We all had rotary telephones in our homes, so there was no question about what that dial was or where it'd come from. Clearly repurposed for this gadget. The lights started coming on, one by one, in an on then off pattern. Working right to left (I think the dial was near the top and don't remember which side it was on - wasn't centered). The dial operated normally: spring loaded return; a stop for your finger to bump against when you had fully dialed it (but had not yet released it so that it could spin back to its parking position). INSIDE the phone itself - if you opened one of them, and I had (at some point) is the 'guts' of the dial, and it has clear windows (plastic case(s) through which you can see the workings. They include like brass strips, very springy, with metal bumps on them, where they face each other. And a cam! The cam operates these switch contacts, as the dial returns to the parked position. That's a clock. It's async - its speed and timing are governed by the mechanism, as well as by just when you let it go. Through gear reduction or drag or such, it does not instantly spring back. Instead, the cam rotates and briefly wedges a springy brass part to get it to separate from its close neighbor. It's a sandwich - there are idk how many strips of brass in there, in an essentially parallel arrangement. No metaphor comes to mind - its its own thing. 'sandwich' is partly right but its a very narrow one! There are solder lugs fixed to this assembly or screw terminals or a combination of those. IT WAS quite possible to dial that same telephone by simply lifting the receiver (handset) and operating the 'hook switch' (the same switch that moves under the weight of the handset as you replace it back onto the telephone 'hook' - which is more of a cradle, often. Depends on the model (kitchen, wall-mounted phones had a Y-shaped metal bracket that received the earpiece part of the handset; the weight of it pulling it down a good half an inch as it was replaced). To dial a '9' (nine) you could quickly depress the hook switch somewhere near eight to ten times (whatever the count was, to do it correctly, did not vary at all, most likely). I would simply fool with it until it started ringing somewhere on the far end of the connection, and quickly hang up -- it had obviously 'dialed out' and I didn't want to find out who's phone I'd just rung. ;) THAT'S GOING to be about my first encounter with a 'computer' -- if we can stretch that definition to include any electro-mechanical (or fully 'electronic') machine that can 'count something, reliably' (and also make some kind of persistent 'display' of what it counted 'from' and/or 'to' - a single-digit number, for base 10 (decimal) for the most part. There might be some other qualifying thing I haven't thought about. So, this would-be computer has a clock - the dial serves this function. It provides the evolution of the system, from moment to moment, and it lets the machine (overall) come to a rest - to stop doing new things. ;) The telco (telephone company) provides part of the computer (well, all of it when you count the telephone in the home ;) What they have there, far away, is a series of electro-mechanical switches (long since replaced by fully electronic ones in more recent times) that are known as 'stepping relays' because, instead of the more usual kind, these relays turn in a circle (like an old automobile ignition under the cap). Can't remember if that's the 'distributor' and 'distributor cap' but as I typed this that seemed right. As the 'pulses' from the rotary telephone in the home 'come in' (are relayed by wire, from the home to the telephone company) the stepping relay takes a 'step' for each part of the dialed number its designed to respond to. A '9' likely gave it 9 steps in total; an '8' dialed makes it step one less than that (8 steps in total) and so on. It can return back to zero - it goes in only one direction, so it has to go past every 'station' in the circle to get back to a neutral (or zero) position. Not sure beyond that how this gets to be more complex, as more and more of the outbound call is dialed (by its number). The guess here is timing provided by the phone company. They would (ostensibly) preserve the very first number dialed, in that first relay, and let it be, from then on. Instead, the next relay at the phone company takes over and registers the next number dialed. And so on, until enough digits were dialed to complete a call (using the 'prefix' dialed as the very first part of the telephone number of an outbound call). You can see how dialing '0' (or "oh!" as it was called) could in fact bring up the telphone operator (an employee at the telco) as a zero dialed probably steps the stepping relay ten times (9 + 1 = 0 here, haha). So that's a computer because it likes everything you dial and places it into a context that does new work (placing telephone calls by /routing them/. More or less. ;) Definitely sparked something of the imagination; the people who built the detailed workings of them certainly had computer-like ideas in their heads at the time. The personal demonstrator for the binary counter (telephone dial and incandescent miniature light bulbs) was certainly in this category. Maybe we didn't really have (or need) a specific name for it. It was fairly easy to figure out how to predict the 'answer' it 'gave' if you dialed a specific 'problem' into it. I don't remember how you reset it to a zero condition (like when the Rubik's cube is fully back to one color per face for all six faces; a known 'state' of the 'machine'). If you think about it, if they gave you a Rubik's cube in an otherwise solitary prison cell, you could keep a journal on it, given a fantastically accurate system for turning the faces of it to produce unique and well-known 'states' for all the little sub-faces that make it up. Could be done. Maybe not by one in a hundred thousand people, but it seems somewhat likely a stubborn person with this ability could do some of that, successfully. Why they'd be blessed with the one and not the other (skill required to operating that 'state machine' reliably, but yet unable to remember the 'journal entries' they would 'store' on the cube!) .. is an excercise left to .. no one, really. It's an absurd case, all the way through it. ;) END.