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| Does a hobbyist need a Oscilloscope? |
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| suicidaleggroll:
--- Quote from: tggzzz on June 30, 2016, 05:21:06 pm ---Sounds like compression wouldn't work with something involving a CLK, CE, DATA. --- End quote --- Why not? --- Quote from: tggzzz on June 30, 2016, 05:21:06 pm ---The very cheap LAs I looked at didn't have a separate CLK input (or it was improperly terminated); instead they relied on asynchronously sampling to infer the DUT's clock. --- End quote --- Yes it's asynchronous, but the sample rate is fast (Saleae is 500 MHz) and it only takes up space when the signal changes states, so does it really matter? --- Quote from: tggzzz on June 30, 2016, 05:21:06 pm ---OK, so stuff can be missed in an operating system; hit-and-miss for logging and post-mortem dumps. --- End quote --- If you shut off logging, then yes you'll miss whatever happens while logging is shut off. I wouldn't really call that "hit-and-miss". If you tell it to grab 5 hours of data, it'll grab 5 hours of data gap-free, provided your system has enough memory to handle it given the activity level of the signals you're monitoring. Something like 115k async serial could be recorded for days, a 50 MHz SPI running full tilt is another story. --- Quote from: tggzzz on June 30, 2016, 05:21:06 pm ---All tools and techniques have their limitations. The extent of those limitations depends on the tools and the system being tested. --- End quote --- Sure, but dumping out everything you want/need to see over a slow uart plugged into a PC running minicom is incredibly limiting. It's useful if your requirements fit within those ridiculously restrictive limits, but if not, that's where a LA comes in. All I'm saying is that for somebody getting into microcontrollers, while ideally he would have both a LA and a scope, if it had to be one or the other he'd get far more use out of a decent LA than a scope IMO. Most of my work is with digital circuits, and while I have a scope, the LA gets far more use. I can't even remember the last time I turned on the scope, it's been at least a year. |
| tggzzz:
--- Quote from: janoc on June 30, 2016, 06:08:56 pm ---I think this is not the thread to argue about what is and isn't an LA. --- End quote --- Just so, as I pointed out in my one reply :) --- Quote ---If Buspirate works for your needs (which seem fairly specific and not typical use cases for a logic analyzer, more a serial terminal, btw!), by all means, do keep using it. --- End quote --- Well, I wasn't the one to raise the serial interfaces point. I don't agree that my points are limited to serial terminals; they are applicable to all comms where there is a series of bits/bytes/messages going in one or more directions. There are too many counter-claims running around, with people claiming tool X is best/required/poor/unnecessary for serial comms. There's some truth in many statements, but too often the balances and caveats are omitted - which makes it seem as if the matter is cut-and-dried. --- Quote ---That's not the point. However, if someone is looking for an LA, Buspirate isn't the best first choice because that function is at best an afterthought in the design of that (otherwise very useful) tool. I have both a Buspirate, two cheap logic analyzers (a cheap Saleae clone and the OpenBench Logic sniffer) and my scope can do some limited decoding as well, but I would never consider that these tools are somehow interchangeable. Each is good for one thing and sucks big time for another. --- End quote --- And that's the balance that is often missing. An engineer will find a way to use whatever is available. Doing more with less is elegant. |
| tggzzz:
--- Quote from: suicidaleggroll on June 30, 2016, 06:11:00 pm --- --- Quote from: tggzzz on June 30, 2016, 05:21:06 pm ---Sounds like compression wouldn't work with something involving a CLK, CE, DATA. --- End quote --- Why not? --- End quote --- How much can you compress the CLK? --- Quote --- --- Quote from: tggzzz on June 30, 2016, 05:21:06 pm ---The very cheap LAs I looked at didn't have a separate CLK input (or it was improperly terminated); instead they relied on asynchronously sampling to infer the DUT's clock. --- End quote --- Yes it's asynchronous, but the sample rate is fast (Saleae is 500 MHz) and it only takes up space when the signal changes states, so does it really matter? --- End quote --- Yes, if it is a 10MHz clock and one message every millisecond; that's 10000 transitions per message --- Quote --- --- Quote from: tggzzz on June 30, 2016, 05:21:06 pm ---OK, so stuff can be missed in an operating system; hit-and-miss for logging and post-mortem dumps. --- End quote --- If you shut off logging, then yes you'll miss whatever happens while logging is shut off. I wouldn't really call that "hit-and-miss". --- End quote --- If it is capturing when a message arrives, that's a "hit". If it is dumping, the message will be "missed"! --- Quote ---If you tell it to grab 5 hours of data, it'll grab 5 hours of data gap-free, provided your system has enough memory to handle it given the activity level of the signals you're monitoring. Something like 115k async serial could be recorded for days, a 50 MHz SPI running full tilt is another story. --- End quote --- Thank you for making my point! --- Quote ---All I'm saying is that for somebody getting into microcontrollers, while ideally he would have both a LA and a scope, if it had to be one or the other he'd get far more use out of a decent LA than a scope IMO. Most of my work is with digital circuits, and while I have a scope, the LA gets far more use. I can't even remember the last time I turned on the scope, it's been at least a year. --- End quote --- LAs can't verify the signal integrity, which is a necessary pre-requisite before it is worth connecting an LA! I often see signal integrity causing problems in other people's circuits, because they haven't understood that there's no such thing as a digital signal. A scope can, OTOH, do some of the things that an LA can - and with some understanding and imagination, is often sufficient. Anyway, off to the Hackspace, where last week I came across exactly such a signal integrity problen: turning on a heater caused a USB link to lose sync. Good luck debugging that with an LA! |
| System Error Message:
a DMM just doesnt compare to a scope, the reason is you can get a decent DSO and configure it as you like when measuring, my scope has an app that shows the measurement value just like a DMM. In my opinion a decent DSO should be the first thing on your list other than a decent soldering set. You still do need a DMM as the portable DSOs cost like gold per weight just for one as good as a bench DSO. So whether you get a bench DSO or a DSO that relies on having a PC connected they can both be useful. If a DSO relies on a PC than all that matters is the bandwidth between device and PC and PC's hardware resources. You will learn a lot from a decent DSO, get one you wont be disappointed as it is also a toy. Technically you could make game apps for DSOs but do EEEs play video games? Some will say you can use peak detects to get accurate measurements but DSOs have them too. |
| nctnico:
3 pages on this simple topic? :palm: Ofcourse a hobbyist needs a scope! Stupid question because a scope is the only instrument which lets you look at the shape of a signal and electronics is all about shapes of signals :rant: |
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