Open Source Oscilloscope, can it be done?

[garboui]

The other day I went searching for an open source or extensible oscope available. PC based devices were the only things that came up. Why is there no bench scope that's open? Is it just not financially practical?

[ataradov]

Well, a couple of ADCs + FPGA used even in entry level scope will cost you close to the price of the real scope. There is really no point.

Plus to debug and tune handmade scope, you need a scope an order of magnitude better, which defeats the point of making a worse one

[garboui]

Granted, the FR and ADC will use u budget, but what if these were closesd blobs and the rest of the UI and processing were open (similar to raspi)?

[ataradov]

I think there is an effort to reverse-engineer firmware and hardware of the Rigol scopes. The problem is, people that want to use their equipment need it to work when needed, not tinker with it. You are already debugging a problem, do you also want to debug the scope?

There is very little to be gained. The UI is not perfect, but it is acceptable, way below the pain point to spend months of development time.

[james_s]

I think one reason this hasn't really happened is that for the cost of the crucial parts, you can buy a used older model scope that will outperform the one you were going to build. Oscilloscopes have tended to be on the bleeding edge, a lot of fancy tricks were incorporated to get them to perform as well as possible, just look inside some of the older Tek scopes. They're an engineering masterpiece.

[JPortici]

well there is the guy who hacked an owon scope..

http://blog.weinigel.se/2016/05/01/sds7102-hacking.html and following. nice reading

[Marco]

Why is there no bench scope that's open? Is it just not financially practical?

Too much effort, too little pay off. Need to wait for the right crazy person to come along and make one.

[kripton2035]

may be a place to start ? https://www.kickstarter.com/projects/342199468/openscope-instrumentation-for-everyone/description

[djnz]

Have you seen this:

Texas Instruments - 50-Ohm 2-GHz Oscilloscope Front-end Reference Design  -> http://www.ti.com/tool/TIDA-00826

Not really open source, but very interesting. Of course, if you actually want to build it, the parts are very expensive.

[spanner888]

Well Bunnie has done one for the Novena laptop with "two 8-bit channels at 1GSPS or one 8-bit channel at 2GSPS with an analog bandwidth of up to 900MHz. As a side bonus we also wired in a set of 10 digital channels that can be used as a simple logic analyzer." Probably not directly what you want but food for thought, especially the front end.

http://www.bunniestudios.com/blog/?p=3957

[ataradov]

ADC used in this design (ADC08D1020) costs ~$400 on DigiKey. I'm sure there are places to get it cheaper, but not much in low quantities.

[tautech]

................... The problem is, people that want to use their equipment need it to work when needed, not tinker with it. You are already debugging a problem, do you also want to debug the scope?

Exactly and reliability was the primary reason years ago I ditched troublesome CRO's in favour of DSO's.

There is very little to be gained. The UI is not perfect, but it is acceptable, way below the pain point to spend months of development time.

I've seen a few threads like this over the years, all with members thinking they can build a better scope than the many that are currently available. 
The functionality in basic entry level DSO's is no trivial task to implement, let alone in more advanced DSO's.

If we take a step back and look at the # of brands that are designing and building DSO's, there really are only a dozen or so which implies if it was easy everybody would be doing it.

[garboui]

................... The problem is, people that want to use their equipment need it to work when needed, not tinker with it. You are already debugging a problem, do you also want to debug the scope?

Exactly and reliability was the primary reason years ago I ditched troublesome CRO's in favour of DSO's.

There is very little to be gained. The UI is not perfect, but it is acceptable, way below the pain point to spend months of development time.

I've seen a few threads like this over the years, all with members thinking they can build a better scope than the many that are currently available. 
The functionality in basic entry level DSO's is no trivial task to implement, let alone in more advanced DSO's.

If we take a step back and look at the # of brands that are designing and building DSO's, there really are only a dozen or so which implies if it was easy everybody would be doing it.

I understand this completely. I do design electronic goods for a living already and know the amount of work required to manufacture something, let alone design something with a degree of complexity to be manufactured reliably and economically.

Something I hinted at originally is working with a hybrid approach. Have a closed source blob, being a skeleton platform; ie. 1054z with basic functional interface (or the same). However the usb, Ethernet and UI will have end user accessible API's to customize UI looks, measurements, data displays etc... IO can be customized for automated tests etc, signal generation, decoding etc.

Doing something like this as a ground up effort would be a massive feat to be profitable/ feasible/ good. Finding a partner company that would allow a rebranding with the custom extensible interfaces may be feasible?

[james_s]

I don't know why a CRO would be any more troublesome than a DSO. I've been using my Tek 465B for 17 trouble-free years now, it's actually quite a lot more dependable than some of the (relatively cheap) DSO's I've dealt with. There are never firmware bugs or lockups with an analog CRO.

[ataradov]

I don't know why a CRO would be any more troublesome than a DSO.

I like to capture signals and look at them in detail, for example. 24 Mpts of memory is pretty handy for that.  I also like to get things int a computer and do math om them from time to time.

If you only look at periodic signals, then may be CRO is good enough.

[tautech]

I don't know why a CRO would be any more troublesome than a DSO. I've been using my Tek 465B for 17 trouble-free years now, it's actually quite a lot more dependable than some of the (relatively cheap) DSO's I've dealt with. There are never firmware bugs or lockups with an analog CRO.

Some aren't, you're right.....when designed conservatively and to last like a good # of the classic Teks like yours.
However by virtue of the the high voltages in a CRO, several blocks of a CRO circuit are under some stress and with the now very common practice of using componentry close to limits, failures ensue.

With many CRO's as I'm on record having said before; you need another to keep the CRO you have in operational condition.
Fixed enough of them to know this for sure. 

[james_s]

I don't know why a CRO would be any more troublesome than a DSO.

I like to capture signals and look at them in detail, for example. 24 Mpts of memory is pretty handy for that.  I also like to get things int a computer and do math om them from time to time.

If you only look at periodic signals, then may be CRO is good enough.

I'm not debating the usefulness, there are indeed times when a DSO will do things that are simply not possible to do any other way. I was only speaking in terms of reliability to the comment about them being troublesome.

[ataradov]

I was only speaking in terms of reliability to the comment about them being troublesome.

Well, in my experience, old CROs almost always have issues with rotary switches. They oxidize, and fail in the most unpredictable way. This is solved with contact cleaner most of the time, but still annoying.

This will probably apply to DSOs as well, but given how cheap they are and improvements made over the years, I'd rather toss a scope after a few years of use anyway, so I'm unlikely to see them fail in any specific way.

[Cloud]

What about this? http://www.scopefun.com/

[ataradov]

What about this?

100 MHz Sampling rate is somewhat slow, memory depth is very low for a modern scope.

There are no hardware files in easily readable format, but I doubt it will be cheaper than $200-300, at which point it again does not make sense. Unless you actually want to have that open source stuff and may be use it in connection with scripting or something like that.

It seems like a nicely designed unit, but not a general use device.

[SaabFAN]

Wasn't there a brand of Scopes that looked like HP-Scopes from the late 90s that were kind of open source?
I remember reading about the FPGA-Program and basically most of the firmware getting rewritten by hobby developers even before the manufacturer of the scopes went bankrupt and these scopes flooded ebay at suspiciously low prices (They're gone now on ebay, which I guess happened for a reason ).

[samofab]

Wasn't there a brand of Scopes that looked like HP-Scopes from the late 90s that were kind of open source?

You mean this one:
https://sourceforge.net/projects/welecw2000a/

[ohdsp]

Would love to build/design an open source oscilloscope. It has been another one of those projects I have had on my to do list for a long time (and no i'm not some delusional moron).

The front end would be my first concern (with a flat frequency/linear phase response and the voltage resolution).

Whilst you would need fast FPGAs to capture the data my thoughts where could you do something clever to interleave multiple channels in a slower device... No idea what it would end up like, and doubt you could beat a Chinese Siglent/Rigol initially with any design. Although most peoples expectations these days seem to be it's either everything you ever wanted and more or it shouldn't exist because why should it take time to develop and improve... Anyway I did have an FPGA dev kit somewhere....

[james_s]

I'm not an expert on oscilloscope design but I think the analog front end and the ADC is where most of the "magic" happens. Once you have the data in digital form that's relatively easy to manipulate. I seriously doubt you'd come close to the performance of a $400 Rigol for twice the price and many tens of hours invested but it could be a fun project none the less.

[SaabFAN]

I think for a bit more money and most likely not that much time to invest, it's possible to build the analog frontend out of ICs.
When looking at all the teardowns of new scopes, it is noteworthy that many manufacturers go the extra mile and build at least part of their frontends out of discrete components to save on the components.

As far as I know, at least TI and Analog Devices have ICs in their portfolio that are more or less specifically designed to be used in Scope frontends (variable gain amps good for frequencies in excess of 300MHz, very high speed single-ended to differential converters, etc.).
These chips aren't cheap though! Prices are about 5 to 9€ and they don't go down that much when bought in quantity, so I see why manufacturers shy away from them and go for a discrete solution that cost maybe 20 cents in components.