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| HaasoscopePro AFFORDABLE open-source open-hardware 2 GHz oscilloscope! |
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| tggzzz:
--- Quote from: haastyle on December 08, 2024, 09:51:27 pm --- --- Quote from: tggzzz on December 08, 2024, 07:34:29 pm --- Having a quick look at your PCB, you don't mention your stackup, the analogue input circuits don't seem to minimise track length, and I wonder if things marked 50ohm in the schematic really are 50ohm. Personally I wish you luck with your kickstarter, but I wouldn't think of investing until you demonstrated it working - preferably plus a review of the prototype by an independent engineer. --- End quote --- Very legitimate concerns! I am writing more about the project over here: https://hackaday.io/project/200773-haasoscope-pro The stackup is 10-layer, sig1 gnd sig2 gnd pwr1 pwr2 gnd sig3 gnd sig4. Impedance controlled pcb of course. I made test boards and tested track impedance with a nano vna plus. It definitely works. I've tested with a Leo Bodner pulse generator with 40ps riserime, and I see about a 200 ps risetime. I'm fine tuning the multi board oversampling now, which will get up to 6.4GS/s, at which point I'll be able to test the bandwidth more accurately. There will certainly be videos, plots, etc demonstrating the performance before the project launches next month. At the moment we are just in pre-launch. There will also be independent reviews. Hopefully even one from Dave again. --- End quote --- Oh... good. You are further ahead than I realised. We look forward to seeing the results :) |
| Nominal Animal:
--- Quote from: tggzzz on December 08, 2024, 11:43:16 am ---Sometimes it is known when creating the schematic that certain PCB rules will have to be followed, e.g, differential pair matched length or impedance control. With simple tool for small designs, those constraints can be simple text annotations. In complex tools for big designs where a different person does the PCB layout, such properties can be entered into the schematic, and the tool will (hopefully) ensure the PCB layout person has complied. --- End quote --- Right. In EasyEDA, selecting different colors for different wires is very easy, so for some examples I've used the wire color to denote different types (power, digital, analog, high-frequency analog video), just to try and see if it makes the schematics easier to understand. (I'm not sure that worked.) But I definitely understand what you're saying. --- Quote from: tggzzz on December 08, 2024, 11:43:16 am ---In the cases where, say, several signals are individually buffered before going off-board (e.g. a control bus with inverters), the schematic designer will wire them up without knowing the detailed PCB layout. That may cause an unnecessarily tangled set of wires, and it is perfectly reasonable for the PCB person to swap pins. Such swaps are then automatically back-annotated into the schematic. --- End quote --- This is the exact reason why I started putting labels on the connectors, instead of drawing wires to the connectors in the schematic: when doing the PCB in EasyEda, it makes it trivial –– just a few clicks –– to change the pin order. With wires, it gets messy. There is now a pin order/editing tool, where one can remap the pins of a component in the schematic editor, but it is way more complicated to use than just moving the net labels around. I'm reassured to understand that what I'm doing is only amateurishly wrong, and not painfully wrong, if you know what I mean. That is to say, what I'm trying to achieve is normal, I'm just not doing it very well yet. If not on the exact correct path, then at least nearby, instead of wandering randomly in the woods. This is kinda-sorta important, because learning is easier than un-learning bad habits, and I was really afraid the functional separation of schematics was wrong. I do believe https://github.com/drandyhaas/HaasoscopePro/blob/main/adc%20board/haasoscope_pro_adc_fpga_board_schematics.pdf is split into too small parts, and would rather see modular units instead of component-level splitting. (I actually have seen similar issues in source code, having individual functions split into separate files, instead of functional "modules". I believe all affected developers had Java (applet) backgrounds, as the web Java applet environment required file name and applet class name to match, IIRC.) As an enhancement suggestion for OP (for at least the main ADC board), I believe it would be nice if each input channel was on the same sheet, spatially grouped showing the preamp/first input stage (left), gain sections, and actual ADC (right). It would allow others with experience in precision/high-frequency ADC designs see the key scheme and details at once, and suggest enhancements. If it means that sheet does not fit an A4/Letter, no problem: use as large a schematic sheet as is needed. --- Quote from: Bud on December 07, 2024, 07:01:55 pm ---What is wrong with you people? --- End quote --- Absolutely nothing: we just don't know better. That's the thing: if you do not tell us what and why we are doing wrong, and tell us how we can do better, how the flying fuck should we know how to do things right? We're not telepaths, and creative analytical engineer-type humans do not learn by simply emulating others: we investigate, examine, and are not satisfied by just what or how, but also exactly why those particular whats and hows should be used. You know, the basic science and engineering stuff. If you cannot or do not want to do it yourself, you can still find a book or video or blog or forum where one can learn how to do better, and just point us that way. If you don't want to do that either, then you're just commenting on how stupid wobbly toddlers look when they're trying to learn to walk, and demanding they stay hidden until they've learned to walk, so they won't upset your sensitive sensibilities with their wobbly toddling. --- Quote from: tggzzz on December 08, 2024, 11:43:16 am ---Fundamentally it is a matter of understandability and good taste. An engineer ought to be able to comprehend the former, but the latter cannot be taught! --- End quote --- "Good taste" is based on intuitive (statistical) analysis of human responses to the stimuli at hand, so while it indeed cannot directly be taught, even analytical barrel-grown hick potatoes like myself can be shown how to develop one. The trick is to point out the things achieved and things avoided when applying good taste. The rest is left to the innate human pattern-recognition abilities. |
| tggzzz:
--- Quote from: Nominal Animal on December 09, 2024, 03:17:06 am --- --- Quote from: tggzzz on December 08, 2024, 11:43:16 am ---Fundamentally it is a matter of understandability and good taste. An engineer ought to be able to comprehend the former, but the latter cannot be taught! --- End quote --- "Good taste" is based on intuitive (statistical) analysis of human responses to the stimuli at hand, so while it indeed cannot directly be taught, even analytical barrel-grown hick potatoes like myself can be shown how to develop one. --- End quote --- Nope. That's "common taste", which is often appalling. :) It is also how ML works, which produces grammatically correct bullshit. That's what many people do, and many people are fooled into believing the bullshit is correct. |
| KE5FX:
--- Quote from: tggzzz on December 09, 2024, 10:19:38 am ---It is also how ML works, which produces grammatically correct bullshit. That's what many people do, and many people are fooled into believing the bullshit is correct. --- End quote --- Eh, that dismissal isn't going to fly for much longer. |
| tggzzz:
--- Quote from: KE5FX on December 09, 2024, 06:20:06 pm --- --- Quote from: tggzzz on December 09, 2024, 10:19:38 am ---It is also how ML works, which produces grammatically correct bullshit. That's what many people do, and many people are fooled into believing the bullshit is correct. --- End quote --- Eh, that dismissal isn't going to fly for much longer. --- End quote --- We'll see. Even stopped clocks are right twice a day. One swallow doesn't make a summer. Etc. |
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