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Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

rtestardi.github.io

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Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#31

Post by burgerone »

serviceberry wrote: post #19

I think projects like that would have been a godsend 2-3 decades ago, when even a basic oscilloscope costed as much as a used car. Nowadays, very good oscilloscopes with 200 MHz bandwidth, good user interfaces, and responsive displays are selling for $300 - I'm talking Siglent, Rigol, UNI-T. So the merits of DIYing something much worse just aren't quite there. It's that one piece of equipment you use to troubleshoot…

In his presentation video [0] Rich explicitly states that his goal is to make electronics approachable for the younger generation. A low barrier of entry in almost all directions is a key component in that in my opinion.

[0]: https://www.youtube.com/watch?v=sbRXDkHS_V0

Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#32

Post by atoav »

Mandatory caveat: beware of ground loops when using a USB oscilloscope! Most budget USB scopes share ground with your PC via the USB port. If you're probing high-voltage circuits (e.g., mains power, switching supplies), this can create a dangerous potential difference, risking damage to your computer or worse. Some scopes offer isolated inputs, but if yours doesn’t, use differential probes or an isolation transformer. Otherwise, you might end up debugging your laptop’s fried USB controller instead of your circuit.

Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#34

Post by jesperwe »

fryd_w wrote: post #29

The flea-scope's hybrid FPGA/MCU architecture for USB streaming is clever - using FPGA pipelining to handle 100MS/s capture paired with an STM32 for protocol translation is sweet cost-wise. BUT, the 8-bit ADC resolution and lack of input protection networks (compared to Rigol's 1MΩ//20pF frontends with overvoltage clamping) make it risky in case of unattenuated signals. The Python analysis toolkit using NumPy/SciPy f…

The specs say 12 bit though.

Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#35

Post by dkjaudyeqooe »

bramhaag wrote: post #28
dkjaudyeqooe wrote: post #16

Earlier quoted context omitted.

> Public domain is not open source, and especially not free (as in freedom) How so? There are no restrictions on use or distribution. > Restricting commercial use is also not free. I agree, and I would include neutering any commercial uses, in which case GPL is non-free.

> How so? There are no restrictions on use or distribution. It's not open source because it does not use an open source license (public domain is not a license). It's not free because this depends on your and the author's jurisdiction (if you both live in the US, then yes there are no restrictions on use or distribution) > I would include neutering any commercial uses, in which case GPL is non-free. In what way does…

Jurisdictions always matter, other OS licenses are also subject to local laws and its not a given they will be valid or interpreted as intended. Arguably it's the intention of the creator of the software that matters in how licenses are actually enforced (or not). So in that sense PD is fine. There are also plenty of easy cures for PD, such as making changes and then copyrighting and licensing that derived work as required.

The GPL forces you to license all your relevant software under restrictive terms (ie under the terms of the GPL). How people can declare that as 'free' I'll never understand, it's just ideological nonsense.

The GPL makes it hard or impossible to make money from your software since anyone else can duplicate and sell it. That's obviously neutering commercial use.

Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#36

Post by burgerone »

nayuki wrote: post #33

Does the software provide a way to export recorded waveforms to allow analysis in other programs? And what is the maximum number of samples it can record?

Recording, exporting and interpreting waveforms doesn't seem to be amongs the objectives of the scope interface.

Over on hackaday [0] Rich explains that you can however easily grab the data directly from the serial port using python and thus record it:

> (07/28/2024) Sorry, there is no protocol analysis -- just digital display. You can invoke a "scope" command by python or something, and get the data yourself in binary -- I have an example of that in StickOS2 repo python/scope.py, but it is very rough. (Analog has additional challenges of having to do calibration, but digital is easy.)

[0]: https://hackaday.io/project/192598-flea-scope-usb-oscillosco...

Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#37

Post by chefandy »

serviceberry wrote: post #19

I think projects like that would have been a godsend 2-3 decades ago, when even a basic oscilloscope costed as much as a used car. Nowadays, very good oscilloscopes with 200 MHz bandwidth, good user interfaces, and responsive displays are selling for $300 - I'm talking Siglent, Rigol, UNI-T. So the merits of DIYing something much worse just aren't quite there. It's that one piece of equipment you use to troubleshoot…

It’s a matter of perspective, though. For a white collar professional in the US? Sure. For most of the world’s population, the distinction between $300 and $18 is extremely consequential.

Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#38

Post by andyjohnson0 »

serviceberry wrote: post #19

I think projects like that would have been a godsend 2-3 decades ago, when even a basic oscilloscope costed as much as a used car. Nowadays, very good oscilloscopes with 200 MHz bandwidth, good user interfaces, and responsive displays are selling for $300 - I'm talking Siglent, Rigol, UNI-T. So the merits of DIYing something much worse just aren't quite there. It's that one piece of equipment you use to troubleshoot…

Nowadays I have a fairly decent Rigol scope, which suffices for my modest and infrequent needs. But back when I was a teenager I had very little money but plenty of time. A cheap DIY option would have made a lot of difference to me. I hope project this makes a difference to people on a budget, of whatever age.

Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#39

Post by serviceberry »

yjftsjthsd-h wrote: post #30
serviceberry wrote: post #19

I think projects like that would have been a godsend 2-3 decades ago, when even a basic oscilloscope costed as much as a used car. Nowadays, very good oscilloscopes with 200 MHz bandwidth, good user interfaces, and responsive displays are selling for $300 - I'm talking Siglent, Rigol, UNI-T. So the merits of DIYing something much worse just aren't quite there. It's that one piece of equipment you use to troubleshoot…

I think there's a difference in options at $200/$20/$2 (see elsewhere in this thread) just in lowering the bar to entry to the point of triviality. I'm not spending $300 without knowing exactly what I want it for, $20 is easy, $2 is an impulse buy.

Fair enough, but on the flip side - you either want to get into electronics or not. If not, there's no real point in spending the money, even if it's $2. If you do, then you probably don't yet have an understanding of what features you need, and the cheapest option will actually hold you back.

Some specific issues: first, the number of inputs. A lot of circuit debugging is about "let's see how signal A looks like when signal B happens" (B might be a bus clock or something like that). So, a lot of the time, you need two inputs, not one.

Second issue: even hobby MCUs generally run faster than 4 MHz, so you might need more bandwidth to monitor I/O, even for old-school Arduino stuff - let alone RP2040.

Third issue: for anything analog, from audio equipment to household appliances, the 0-6 V input range just doesn't cut it.

I'm not trying to dunk on this project: I think it's about as good as you can do for the price, and it's clearly a passion thing for the author. But if you can afford it, and if you want to learn electronics, a "real" oscilloscope is almost certainly a better deal.

Re: Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

#40

Post by burgerone »

atoav wrote: post #32

Mandatory caveat: beware of ground loops when using a USB oscilloscope! Most budget USB scopes share ground with your PC via the USB port. If you're probing high-voltage circuits (e.g., mains power, switching supplies), this can create a dangerous potential difference, risking damage to your computer or worse. Some scopes offer isolated inputs, but if yours doesn’t, use differential probes or an isolation transformer…

On page 9 of the linked document Rich also addresses this and calls for the use of a full-speed usb isolator
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