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Bloody posted:Also ten megs on a breadboard is going to be fine, your tenth order harmonics are still more than a meter and the parasitics will be irrelevant I was going by the last post in this thread on the 68 Katy and the other site linked from it which made me think running a >1 MHz bus onto a breadboard would be problematic.
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Dec 26, 2014 06:19
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eschaton posted:I was going by the last post in this thread on the 68 Katy and the other site linked from it which made me think running a >1 MHz bus onto a breadboard would be problematic. well if you have long looping wires you're making antennas which needless to say is bad
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Dec 26, 2014 06:41
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10 MHz on a breadboard is possible as long as you keep in mind to build everything as compact as possible
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Dec 26, 2014 06:52
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hobbesmaster posted:well if you have long looping wires you're making antennas which needless to say is bad Which, at 10 mhz, need to be nearly a meter in length to be relevant to your tenth order harmonic (which is pretty dang irrelevant, you can get by just fine with like less than fifth order)
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Dec 26, 2014 07:11
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Back in school we built an arm7 system on a solderless breadboard with like memory buses and poo poo running all over the place and those effects were by far the least of our issues
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Dec 26, 2014 07:12
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Olivil posted:10 MHz on a breadboard is possible as long as you keep in mind to build everything as compact as possible Do this, but also don't sweat it
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Dec 26, 2014 07:13
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If 10x your frequency is still long relative to whatever you're doing, then nothing matters
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Dec 26, 2014 07:14
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Bloody posted:Back in school we built an arm7 system on a solderless breadboard with like memory buses and poo poo running all over the place and those effects were by far the least of our issues that's pretty cool i'd like to design something with like DDR2 RAM but apparently it's really hard to get right idk i mean i think you're supposed to start with easier poo poo like just a microcontroller with integrated flash and sram but unfortunately that's not very useful for what i have in mind, it needs to have a bunch of io but also a tcp/ip stack and being able to run high level poo poo like http and that basically means linux (no i am not going to use uip)
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Dec 26, 2014 07:16
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Mr Dog posted:that's pretty cool It's not so much hard as just expensive. With stuff like that you have to start caring about impedance controlled traces and that generally means lots of layers and things like termination and now you've got an eight layer board with bga components and microvias and that poo poo sucks at least at a hobbyist level Although for what you're looking for I dunno something like tis new m4s could work maybe? Tm4c I think?
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Dec 26, 2014 07:20
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eschaton posted:surplus post would be a nice yosmas present Paging yosposter Raluek, paging Yosposter Raluek please report to low level thread
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Dec 26, 2014 09:03
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Jonny 290 posted:do we need a separate surplus thread, or should i just megapost Wanna see this post
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Dec 26, 2014 19:39
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ill do it up. IRL intervening right now
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Dec 26, 2014 21:05
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All this talk of clock speed, and no mention of edge rate 10Mhz tells you the period of the signal, doesn't tell you poo poo about the edge rate of the signal; if you've got some shiny new parts driving 10mhz on a tiny rear end process, you could have near sub-ns rise times, which is a frequency much higher than 10mhz here's a good explanation: http://www.freelists.org/post/si-list/3dB-or-Knee-Frequency,3 Si-list is legit, even if it's sometimes full of grey beard fights, but these guys design 100G+ telecom backplanes, so I listen
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Dec 26, 2014 21:10
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movax posted:All this talk of clock speed, and no mention of edge rate thanks! for me, I'm specifically talking about NuBus. I'm not sure how to figure its edge rate, but it's specified as 75ns unasserted, 25ns asserted, with signals asserted on the rising edge and sampled on the falling edge of its active-low bus clock. Edit: Found more detailed timing info towards the end of the pdf I linked. looks like it's not too bad... eschaton fucked around with this message at 22:03 on Dec 26, 2014 |
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Dec 26, 2014 21:40
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can someone help me pick out a display to buy to hook up to a microcontroller? previous experience: making a single 7-segment display spell out "yourE gAy" one letter at a time. I'm looking at stuff like this http://www.adafruit.com/products/661 http://www.adafruit.com/products/358 but I dunno what products/stores are good I don't have any specific goal in mind I just wanna buy one and goof around with it
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Dec 27, 2014 20:07
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Tin Gang posted:can someone help me pick out a display to buy to hook up to a microcontroller? previous experience: making a single 7-segment display spell out "yourE gAy" one letter at a time. they're pretty simple these days i think, get an SPI interface board, load the library, start drawing boxes and sending text
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Dec 27, 2014 20:10
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Tin Gang posted:can someone help me pick out a display to buy to hook up to a microcontroller? previous experience: making a single 7-segment display spell out "yourE gAy" one letter at a time. adafruit makes arduino libraries for all their screens as far as I know, I had a 96x64 oled that I was able to easily get bmps pushed out onto and do some sprite animations for a dumb gift
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Dec 27, 2014 20:57
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just bought a Fluke 115, its not an 87V but it's pretty nice. would have been nice to have a mA scale though, but it's good enough
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Dec 27, 2014 23:12
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movax posted:All this talk of clock speed, and no mention of edge rate ya and all your shitass parasitics are gonna demolish those edge rates
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Dec 27, 2014 23:18
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crosspostingZeether posted:Some guy got Quake running on an oscilloscope: http://www.lofibucket.com/articles/oscilloscope_quake.html
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Dec 28, 2014 21:27
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Holy poo poo
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Dec 28, 2014 22:24
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Olivil posted:crossposting 
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Dec 28, 2014 23:27
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I now have an HP 1660CS logic analyzer and scope! (pods and clips are on the way.) so far I've used the scope to view the action in a little 555 blinker. total overkill, sure, but it was fun to see the hardware I just picked up do something besides boot. also, it gave me the idea that I should also be able to diagnose and repair my digital tuner (a Korg DT-1) pretty easily now. I could also do that with a just multimeter, of course. I've also set it up on my network, and downloaded the user and programming guide PDFs from
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Dec 29, 2014 01:02
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movax posted:All this talk of clock speed, and no mention of edge rate im a mathematician who snuck into signals and hardware thru a couple of end-arounds, i don't really understand this post but i feel like i should
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Dec 29, 2014 02:54
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fritz posted:im a mathematician who snuck into signals and hardware thru a couple of end-arounds, i don't really understand this post but i feel like i should what's the Fourier transform of the unit step function?
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Dec 29, 2014 03:37
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welp the guy that i bought my fluke 115 from lost it so he refunded me just stepped up to a fluke 179, p hyped
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Dec 29, 2014 08:49
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fritz posted:im a mathematician who snuck into signals and hardware thru a couple of end-arounds, i don't really understand this post but i feel like i should digital signals are defined by logic highs and lows and once you get to high rates of throughput the electrical characteristics of the traces and parasitic effects start to interfere so you must design around this and pull a lot of rabbits out of your rear end I'm not an EE but I hope that explanation is more or less accurate
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Dec 29, 2014 10:32
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hobbesmaster posted:what's the Fourier transform of the unit step function? it's going to have power @ all frequencies? and so this: Mido posted:digital signals are defined by logic highs and lows and once you get to high rates of throughput the electrical characteristics of the traces and parasitic effects start to interfere so you must design around this and pull a lot of rabbits out of your rear end means that channel effects come in and act as a filter that needs to be dealt with?
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Dec 29, 2014 21:42
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yeah. every trace is now a capacitor to some neighboring trace and/or ground, as well as an inductor along its length. this makes a low pass filter that is going to soften your rise and fall times
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Dec 29, 2014 21:46
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fritz posted:it's going to have power @ all frequencies? it's hard for us to make perfect square waves in nature (impossibru), so in reality the edges do have non-infinite slope. smaller, faster transistors can drive these edges incredibly fast compared to larger, slower transistors from last decade ill try to sketch something when I'm back home
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Dec 29, 2014 21:48
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effortpost on single ended logic: the real issue also involves the speed of signal transmission, the speed of light is finite in a wire (and in free space), in a pcb its around half the free space speed if a digital line is 1 ns long (~5-6" in a PCB, or around 1 standard western dick) and you're driving a signal that takes 10 ns to move from 0 to 1, no problem, if it takes 100ps then you need to terminate the signal properly or the signal edge will reflect when it reaches the end of the line and come back, if the source isn't matched either it tends to keep bouncing back and forth until it settles. series termination is preferred where possible since it's simple and just means adding a resistor to each line at the worst, sometimes AC termination is used but this tends to cause more problems than it solves in my experience the voltage at the signal input may have oscillated a few times before settling, which can cause real problems if the voltage at the end of the line oscillates down to logic 0 before settling, fast logic may pick this up as a double clock, even if the actual clock speed is slow as balls additionally the capacitance in the line needs to be charged at the slew rate (rate of voltage change) if there's a lot of inductance between the grounds of two devices then that fast edge will create a voltage between "true ground" and the driver and the receiver grounds, which further reduces the signal to noise ratio this is why fast logic and solderless breadboards dont play nice together, the leads used for power and ground are just too long for real fast poo poo the bond wires inside the package cause the same problem, which is why modern ICs often come with a big ground pad in the middle (QFNs, some QFPs etc.), DIP packages are usually right out since the pin spacing forces long bond wires inside the package that may actually make the IC unusable CMOS logic basically connects each output to either VCC or ground, which also means that for most devices the current draw of a CMOS device is very low until you try to drive an output, when going from 0 to 1 on the output the driver will be connected from ground to VCC, the current going into the line (charging all that capacitance) has to come from the power supply, so the current waveform of a CMOS device will be a series of pulses with the same rise time and frequency as the sum of all the outputs, i.e. a series of very high frequency pulses if you forget to put bypass caps near the IC then the inductance in a power supply lead will cause the supply voltage to sag during the transitions, this results in a lovely signal on the output, and may cause problems for the IC if the voltage drops below the minimum operation voltage this is one of the many reasons LVDS and similar differential serial protocols are heavily used in modern designs, ground potential between devices matters a lot less when the signal is differential and ideally the sum of the current draw when two outputs are differential is more or less constant
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Dec 30, 2014 00:27
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longview posted:effortpost on single ended logic: v interesting, thanks
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Dec 30, 2014 00:42
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basically at speed everything is a transmission line
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Dec 30, 2014 00:53
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Hed posted:basically at speed everything is a transmission line gently caress transmission lines and emc
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Dec 30, 2014 02:36
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fritz posted:it's going to have power @ all frequencies? was just getting at that if you want to analyze how good your square wave is you would need a significantly faster scope than you'd think if you just looked at the nyquist frequency this was covered by other posters in significantly greater details
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Dec 30, 2014 02:42
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whats a good cheap (<200$?) function generator? mostly need it for audio (aka low as f) frequencies and to calibrate 100 MHz analog oscilloscope (meh) not afraid to buy used or analog i was leaning toward an old Wavetek 182a (4MHz) but i havent given it more than 10 minutes
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Dec 30, 2014 08:05
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Olivil posted:whats a good cheap (<200$?) function generator? an arduino 
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Dec 30, 2014 08:14
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Mido posted:an arduino please proceed i must have a spare uno somewhere 
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Dec 30, 2014 08:19
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hey fuckers my cool dad has a basement full of 70s-80s test equipment, mostly hp stuff he repaired himself, plus some newer things. i hardly know what any of it does but i see the posts in this thread all "i could use an XXXXX" and i'm like, oh yeah we got one of those. and no you can't have it. just making sure you know that your hobby is exactly the same as everything else: dominated by people who are older and richer, and therefore better, than you
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Dec 30, 2014 08:20
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Olivil posted:please proceed i must have a spare uno somewhere generate wave forms, push them onto the DAC, pray the DAC characteristics aren't total poo poo
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Dec 30, 2014 08:24
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