Old analogue scopes beat new digital scopes, for bit-bashed digital outputs

[tggzzz]

the 250Mb/s 4ns serial bit rates bashed out of the processor.

...which you tried to look at on an old 50MHz DSO before pronouncing your verdict. 

Read what I wrote in the first post, concentrating on the second paragraph "The standard statement...". Other people seem to be able to understand that, and to be able to concentrate on the essential points.

[Fungus]

Read what I wrote in the first post, concentrating on the second paragraph "The standard statement...".

Well:
a) It's usually applied to the 100MHz DS1054Z, not an old clunker of a "Rigol"
and
b) You still haven't posted a screenshot of what happens if you output more than four 1's in your program.

[kcbrown]

The Rigols are good value for money, and sufficient for many purposes. But they are not as good as some people claim for some relevant use cases (bit-bashed signals).

Well of course they're not as good for bit-banged signals if the analog characteristics of the signal fall outside the analog capabilities of the scope!  That doesn't make the analog scope the proper tool for the job, however, especially since the analog scope doesn't have single-shot capture capability, much less protocol decode capability (we're talking about beginners here -- how many of them are going to be interested in manually decoding the signal they see on the screen when they don't have to?).  And yes, a logic analyzer is a better tool for doing protocol decode, but if you're trying to track down an analog domain glitch in your digital signal, having the decoded data for context at the same time you see the glitch on the screen may prove invaluable, no?

The Achilles heel of the analog scope is the lack of single-shot capture -- now you're dependent upon a quickly (in human terms, at least) repeating pattern, which may or may not be reasonably possible to generate, to make it possible to see anything at all.


As you noted in your original message, the proper tool depends on the context.   Context matters, a lot, and that is just as true of the advice generally given to beginners as anything else.

I expect that the advice given to most beginners is based on the presumption that they'll be using lower speed microcontrollers (Arduino and the like).  The microcontroller you're using is amongst the faster ones, with (if I'm not mistaken) an internal clock of 60MHz (I wasn't able to find a datasheet on the processor your development board uses, and had to guess on the basis of the number of cores and the total MIPS, as described in the hardware manual for your board: https://www.xmos.com/download/private/startKIT-Hardware-Manual%281.3%29.pdf.  And that presumes one instruction per clock per core).

Also, the scope that is usually recommended today (the Rigol DS1054Z) might or might not show some of the erroneous artifacts that your digital scope is showing, particularly since it claims to have real peak detect.

And finally, the digital scopes that are available to beginners and that are within their usual budget are getting faster.  See, e.g., the Siglent SDS1202X-E (which has 200MHz bandwidth).


Now, I've definitely noticed the trend towards faster microcontrollers, but even so, we're talking about beginners here.   They'll tend to be using whichever platform has the best community support precisely because they're beginners and will benefit more from that support than they would from using a faster, but more esoteric, microcontroller solution.  That platform is currently the Arduino.  There are some, e.g. the STM32, which are getting better, but the Arduino is the mainstay for now.

If a beginner is doing bit banging at a rate that exceeds the capability of the Rigol DS1054Z (at least in hacked form), then he's either unusual or he's not really a beginner, at least in the sense I'm thinking of.

[tggzzz]

Read what I wrote in the first post, concentrating on the second paragraph "The standard statement...".

Well:
a) It's usually applied to the 100MHz DS1054Z, not an old clunker of a "Rigol"
and
b) You still haven't posted a screenshot of what happens if you output more than four 1's in your program.

Sigh. According to the Rigol website, the ds1054z is 50MHz https://www.rigol-uk.co.uk/Rigol-DS1054Z-Digital-Oscilloscope-p/ds1054z.htm

Do you have anything helpful to contribute this conversation? Since other people manage to achieve that, I'm left wondering what your motivation is.

Anyway, I'll respond to any helpful comments you might make in future.

[Mechatrommer]

Scopes should be used to ensure signal integrity.

suggesting a 350MHz CRO to beginner to ensure signal integrity of a sub ns risetime signal is ridiculous..

[ebastler]

we're talking about beginners here.   

I'm pretty confident that any beginner has long since stopped reading this rather childish exchange.
(Not talking about you, kcbrown, but the two grumpy old men carrying on this sorry thread...)

Jeez, this started as a way to get tggzzz over a boring Sunday afternoon, but it's Tuesday now! 

[2N3055]

I apologize for being daft, but would you please explain what do you want to prove here..
I read first post several times (my english is not very good) and I think that you wanted to prove following statement:

"I think it is wrong to give too generalized advice to beginners what first scope to buy.
Everybody seem to say that very low end digital scopes are always better than good used high end analog scopes.
That is not true.
Digital scopes do have many good functions that analog scopes don't have, but these days some of the small CPU development boards work at such frequencies
that these toy 50MHz scopes won't work. Old analog scope that is not best tool for digital work, but if it has enough bandwidth you will be at least able to see something undistorted.
And by clever technique, you might even be able to do the work, as opposed the toy scope that will not be useful at all at those frequencies and signals. "

Is that it?

Because if that is what you think I agree 100%.
But you yourself used wrong GENERALIZATIONS to prove it...

1. Average low end dev kit is Arduino or something like that. Definitely not something that has high speed SERDES interface on it..
2. NOBODY recommends DS1052E to anybody, since like 3-4 years ago.. Recommendations for entry level are DS1054Z, or Siglent SDS1202X-E, or older good analog scopes if you can get good one for cheap.
You cannot make DS1054Z make that waveform that you show, even the 50MHz version one... Siglent SDS1202X-E is 200MHz, definitely would work for this just fine.
3. Where I live you cannot get good old high end analog scope for the money you are saying. There aren't any, and importing, shipping and handling and crap like that it gets to 800-1000€ easy..
NO, we are not retarded, we just live in places where there isn't a good second hand market for T&M equipment...

So I'm really confused.. You tried to relay a good point that I agree with 100%, by choosing methodology that is wrong.

For this particular case I would recommend a Siglent SDS1202X-E because it is 200MHz. Although, I think DS1054Z would show usable info too...

Best regards,

Sinisa

[kcbrown]

we're talking about beginners here.   

I'm pretty confident that any beginner has long since stopped reading this rather childish exchange.
(Not talking about you, kcbrown, but the two grumpy old men carrying on this sorry thread...)

Jeez, this started as a way to get tggzzz over a boring Sunday afternoon, but it's Tuesday now! 

 

Well, seeing how the original message was about advice given to beginners, I think the real target audience is those who are giving advice, not the beginners themselves.   Can't say whether advice-givers are still reading the thread. 

[Fungus]

I apologize for being daft, but would you please explain what do you want to prove here..

[tggzzz]

The Rigols are good value for money, and sufficient for many purposes. But they are not as good as some people claim for some relevant use cases (bit-bashed signals).

Well of course they're not as good for bit-banged signals if the analog characteristics of the signal fall outside the analog capabilities of the scope!  That doesn't make the analog scope the proper tool for the job, however, especially since the analog scope doesn't have single-shot capture capability, much less protocol decode capability (we're talking about beginners here -- how many of them are going to be interested in manually decoding the signal they see on the screen when they don't have to?).  And yes, a logic analyzer is a better tool for doing protocol decode, but if you're trying to track down an analog domain glitch in your digital signal, having the decoded data for context at the same time you see the glitch on the screen may prove invaluable, no?

The Achilles heel of the analog scope is the lack of single-shot capture -- now you're dependent upon a quickly (in human terms, at least) repeating pattern, which may or may not be reasonably possible to generate, to make it possible to see anything at all.


As you noted in your original message, the proper tool depends on the context.   Context matters, a lot, and that is just as true of the advice generally given to beginners as anything else.

I expect that the advice given to most beginners is based on the presumption that they'll be using lower speed microcontrollers (Arduino and the like).  The microcontroller you're using is amongst the faster ones, with (if I'm not mistaken) an internal clock of 60MHz (I wasn't able to find a datasheet on the processor your development board uses, and had to guess on the basis of the number of cores and the total MIPS, as described in the hardware manual for your board: https://www.xmos.com/download/private/startKIT-Hardware-Manual%281.3%29.pdf.  And that presumes one instruction per clock per core).

Also, the scope that is usually recommended today (the Rigol DS1054Z) might or might not show some of the erroneous artifacts that your digital scope is showing, particularly since it claims to have real peak detect.

And finally, the digital scopes that are available to beginners and that are within their usual budget are getting faster.  See, e.g., the Siglent SDS1202X-E (which has 200MHz bandwidth).


Now, I've definitely noticed the trend towards faster microcontrollers, but even so, we're talking about beginners here.   They'll tend to be using whichever platform has the best community support precisely because they're beginners and will benefit more from that support than they would from using a faster, but more esoteric, microcontroller solution.  That platform is currently the Arduino.  There are some, e.g. the STM32, which are getting better, but the Arduino is the mainstay for now.

If a beginner is doing bit banging at a rate that exceeds the capability of the Rigol DS1054Z (at least in hacked form), then he's either unusual or he's not really a beginner, at least in the sense I'm thinking of.

Those are fair points, and I have no strong arguments with them.

The scope I'm using does have "peak detect" (ahem), and as I indicated, it does indeed give the stable result you would expect - unlike the "normal" setting. IMNSHO, envelope detect ought to be the normal mode.

Your point about the Arduino ecosystem's attraction for beginners is correct and important. Personally I find the StartKit easier to program than the Arduino, but that is very subjective and dependent on the problem at hand.

The XMOS processor in the StarKit is one of their low-end ones; according to DigiKey they go up to 32 cores and 4000MIPS. The StartKit is about half the price of a bog-standard Arduino (~£26/£12). Hence I feel justified in regarding the StartKit as "beginner level".

[tggzzz]

I apologize for being daft, but would you please explain what do you want to prove here..
I read first post several times (my english is not very good) and I think that you wanted to prove following statement:

"I think it is wrong to give too generalized advice to beginners what first scope to buy.
Everybody seem to say that very low end digital scopes are always better than good used high end analog scopes.
That is not true.
Digital scopes do have many good functions that analog scopes don't have, but these days some of the small CPU development boards work at such frequencies
that these toy 50MHz scopes won't work. Old analog scope that is not best tool for digital work, but if it has enough bandwidth you will be at least able to see something undistorted.
And by clever technique, you might even be able to do the work, as opposed the toy scope that will not be useful at all at those frequencies and signals. "

Is that it?

Because if that is what you think I agree 100%.

Yes, to a good approximation.

But you yourself used wrong GENERALIZATIONS to prove it...

I made some specific points, with caveats, and used them as an examples of more general issues.

1. Average low end dev kit is Arduino or something like that. Definitely not something that has high speed SERDES interface on it..

See my previous response (written after you posted this) as to why I think it can be justified.

2. NOBODY recommends DS1052E to anybody, since like 3-4 years ago.. Recommendations for entry level are DS1054Z, or Siglent SDS1202X-E, or older good analog scopes if you can get good one for cheap.

Too many of the comments on this forum completely dismiss working old analogue scopes; that's wrong. I'm not aware of specific differences between the 1052 and 1054, but the Rigol website says they are both 50MHz.

You cannot make DS1054Z make that waveform that you show, even the 50MHz version one... Siglent SDS1202X-E is 200MHz, definitely would work for this just fine.
3. Where I live you cannot get good old high end analog scope for the money you are saying. There aren't any, and importing, shipping and handling and crap like that it gets to 800-1000€ easy..
NO, we are not retarded, we just live in places where there isn't a good second hand market for T&M equipment...

I don't see why you wouldn't see the same thing with a 1054. I have no comment about the 1202; clearly 200MHz ought to help.

As for price in your location, clearly that is a very important factor - and I would almost certainly come to the same conclusion.

So I'm really confused.. You tried to relay a good point that I agree with 100%, by choosing methodology that is wrong.

For this particular case I would recommend a Siglent SDS1202X-E because it is 200MHz. Although, I think DS1054Z would show usable info too...

Thank you for some thoughtful points.

[kcbrown]

Those are fair points, and I have no strong arguments with them.

The scope I'm using does have "peak detect" (ahem), and as I indicated, it does indeed give the stable result you would expect - unlike the "normal" setting. IMNSHO, envelope detect ought to be the normal mode.

But it apparently doesn't function the way one would normally expect it to, whilst the DS1054Z's apparently does (assuming, of course, that the feature actually behaves the way the manual describes.  I expect we would have heard complaints about it long before now if it didn't).

Your point about the Arduino ecosystem's attraction for beginners is correct and important. Personally I find the StartKit easier to program than the Arduino, but that is very subjective and dependent on the problem at hand.

The XMOS processor in the StarKit is one of their low-end ones; according to DigiKey they go up to 32 cores and 4000MIPS. The StartKit is about half the price of a bog-standard Arduino (~£26/£12). Hence I feel justified in regarding the StartKit as "beginner level".

"Beginner level" for a piece of hardware isn't measured by hardware capability within its family line, it's measured by  the ease with which someone who doesn't know the first thing about these things can jump in and learn how to make it do his bidding.   That's determined by a number of things, such as the amount of support in the community there is for it, the availability of hardware and software for it, the availability of example code, etc.

If the XMOS StartKit were the most popular and well-supported microcontroller development platform out there (i.e., if it occupied the place the Arduino currently occupies) then your objection to the standard advice given to beginners would be a lot more valid.  But then, if that were the situation, the advice given to beginners would be much different from what it currently is.   Context matters.

Interestingly, though, if that were the actual situation, then I suspect higher-bandwidth entry-level scopes would have come onto the scene earlier simply due to the demand.   I suspect that, as microcontrollers get faster, the entry level T&M hardware will get faster to match.  We're already seeing some of that right now.

[tggzzz]

I actually find it difficult to believe that the 50 MHz DS1052E (or any oscilloscope) produced that result unless it was broken; to me it looks more like a probe problem.  tggzzz, your original post says that you used a 1.5GHz Z0 (low-z?) probe but could you describe the probe in more detail? How was it connected to the DS1052E? Was it through the needed feedthrough termination? It should not matter but was the same feedthrough termination used on the 2465 or was its internal termination used?  Could the DS1052E have been damaged before the test?

A sensible doubt, sensible observations, and sensible questions.

Probe: HP10020A.
50ohm termination: Greenpar BNC inline/feedthrough which ought to be good to at least a GHz. I haven't seen such effects when I've used them in the past, but that is a weak statement.
Rigol damage: I've borrowed the Rigol, but I believe it hasn't been used much. I've no reason to believe damage, and both channels are the same.
2465: internal termination.

Like you I think feedthrough-vs-internal termination "should not matter", but that is undoubtedly an unnecessary extra variable. I'll check it at the earliest opportunity (not tonight).

Unfortunately I haven't got any active probes to use as a comparison, and I certainly wouldn't trust my high impedance passive probes with a 1ns edge rate.

[Mechatrommer]

I'm not aware of specific differences between the 1052 and 1054, but the Rigol website says they are both 50MHz.

then you missed the long memory, 4 channels and level graded display. i hope the 1052 you are testing is the hacked unit to 100MHz, otherwise you just proved you ignorance. its ok you may carry on, your english is too good that nobody can understand, you may play with your bit-bashed signal integrity to the next weekend through your phosphor graded CRO.

I suspect that, as microcontrollers get faster, the entry level T&M hardware will get faster to match.  We're already seeing some of that right now.

how many beginner's level (cheap) I2C or SPI chips you see today that's necessitate 200Mbps rate? (or even close to it)

[kcbrown]

Too many of the comments on this forum completely dismiss working old analogue scopes; that's wrong. I'm not aware of specific differences between the 1052 and 1054, but the Rigol website says they are both 50MHz.

The DS1054Z is easily hackable to 100MHz.   I believe the same is true of the DS1052E.

The differences between the two are quite substantial.  For instance, the DS1054Z is (with the right settings) capable of a waveform update rate in the 30,000 per second range.

You cannot make DS1054Z make that waveform that you show, even the 50MHz version one... Siglent SDS1202X-E is 200MHz, definitely would work for this just fine.

You're making a lot of presumptions here.  The sampling rate of the DS1054Z is 1GS/s.  The frequency response of the DS1054Z doesn't just fall off a cliff after 50MHz.  See this thread for more details: https://www.eevblog.com/forum/testgear/pulse-generator-rise-time-and-rigol-ds1054z-bandwidth/

The frequency response of a typical DSO is not Gaussian: http://literature.cdn.keysight.com/litweb/pdf/5988-8008EN.pdf

[2N3055]

DS1000Z series has 24 times the memory depth than DS1000E series. It has much more advanced acquisition engine that has real "Peak detect" (single shot).
Also most people "unlock it" to 100MHz version (it is sort of something Rigol seems to not mind for hobby use), in which case it has pretty much 120MHz+ -3dB bandwidth.
So I think it would show your example reasonably enough, though edges would not be as clean...

But I would like to point out, that most of beginners ( and professionals  too, on simpler projects) are mostly monitoring communication from CPU to peripheral chips, using SPI, I2C, 1-Wire,   RS232 and RS485 (async serial, at low speeds up to 115200 bps) and such.. No SERDES connected high speed A/D or D/A converter running 10s or 100s of MS/Sec.. That is an advanced project, with serious DSP code behind it and such...

Regards,

Sinisa

[kcbrown]

how many beginner's level (cheap) I2C or SPI chips you see today that's necessitate 200Mbps rate? (or even close to it)

You don't, yet.  But with a general-purpose DSO, that's not the only kind of thing you'd be interested in anyway.  It's a general purpose tool, which means you'd be using it to see all sorts of things.  The faster the microcontroller, the closer the spacing of digital signal events that you're likely to be interested in.

Now, there's something that hasn't yet been mentioned but which is quite important.  And that is that it's probably not an accident that entry level microcontrollers are relatively slow.  The faster the microcontroller, the faster your T&M equipment has to be in order to really keep up.  But perhaps more importantly, the faster the microcontroller and the signals it produces, the greater the importance of the analog transmission line characteristics of the links carrying those signals.   Get fast enough and proper endpoint termination, as well as signal leakage, etc., becomes very important.   And perhaps most important of all for a beginner, you can no longer use breadboards for prototyping if your signals are fast enough.

Which is to say, ease of experimentation is also a monumentally important consideration.  Having to solder up a protoboard, and especially to do so while considering things like the crosstalk characteristics of parallel signal lines, is something that is well beyond any real beginner, and yet that's exactly what you have to deal with once your data rates get high enough (100MHz territory, from what I'm reading). 

For these reasons, I don't expect beginner territory to change all that radically even if microcontrollers can be faster.

[Fungus]

Code: [Select]

    while (1) {
        outPort <: 1;
        outPort <: 1;
        outPort <: 1;
        outPort <: 1;
        outPort <: 0;
  ...

"First thou pullest the Holy Pin. Then thou must count to four. Four shall be the number of the counting and the number of the counting shall be four. Five shalt thou not count, neither shalt thou count three, excepting that thou then proceedeth to four. Six is right out. Once the number four, being the number of the counting, be reached, then lobbest thou the code in the direction of thine DSO, who, being naughty in my sight, shall snuff it."

[xrunner]

"First thou pullest the Holy Pin. Then thou must count to four. Four shall be the number of the counting and the number of the counting shall be four. Five shalt thou not count, neither shalt thou count three, excepting that thou then proceedeth to four. Six is right out. Once the number four, being the number of the counting, be reached, then lobbest thou the code in the direction of thine DSO, who, being naughty in my sight, shall snuff it."

 

[rstofer]

Having come from a 10 MHz scope prior to my Tek 485, I had to come up with some tricks to figure out how to display things that were beyond the bandwidth.

One approach that always works is to slow down the clock.  Get the system to work and then see what happens when the clock is restored. Does it still work?

Another approach is to code simple loops over the offending peripheral.  Even with the 485, I can't see an SPI transaction that occurs once per second with a clock of 10 Mhz.  It's done and gone before the trace is even visible.  Loops help.  So does a DSO with single shot mode.

XMOS seems cool, I might find an application for it some day.  It's a beginner level device in the same way an FPGA is a beginner level device.  It depends on where you are beginning from.  There are some folks who majored in hardware design in grad school...

The OP has been around here a long time (over 5,000 posts) so it seems a little disingenuous to not know that the DS1054Z is easily, and properly, unlocked to 100 MHz.  It's not a hack, it's not hardware changes, it is simply selecting a different analog filter that is known to exist.  A feature designed into the hardware so the same device could be sold with two different bandwidths.  He knows this but chooses to ignore it.

It's tough to recommend a scope to a real beginner - one without an MS in hardware design, for example.  Yes, an analog scope will work but...  It will have no features in comparison to a DSO.  It may, or may not, work and stay working.  The buyer may, but probably won't, be able to fix it.  Beginner, remember?  And no warranty!

Beginners can't even spell bandwidth much less understand the implications when thinking about square waves.  Odd harmonics?  What's that about?  I need how many?  Well, how many are there?  Und so weiter.

Then they show up with a minimal budget.  A used analog scope is the only alternative.  Now it's just a matter of making the least bad choice from what is available.  And hoping...  Hoping is good but not always helpful.

And then there is the cost of shipping...

I just don't have a recommendation for someone with a $100 budget.  Once those school scopes are gone, there may not be any decent choices.

I like the idea of the SDS1202X-E and I'm waiting for the first firmware upgrade.  After several upgrades the DS1054Z is stable.  There's still a spelling error but I'm falling into the 'inside joke' camp.  Who cares?

Unless the beginner has a specific need for a much higher bandwidth, I'm sticking with these.  If they need bandwidth and they don't have money, I guess it's off the eBay and seeing how it all works out.  The beginner can work for decades with microcontroller projects and not outrun the DS1054Z.  Even FPGA projects seldom toggle pins beyond 50 MHz.  Yes, the SDS1202X-E would be a better choice in this case.

And, yes, I expect the Arduino to be the uC of choice for beginners for a very long time.  There's a ton of projects on the Internet and a lot of support groups.

[Mechatrommer]

But with a general-purpose DSO, that's not the only kind of thing you'd be interested in anyway.  It's a general purpose tool, which means you'd be using it to see all sorts of things.  The faster the microcontroller, the closer the spacing of digital signal events that you're likely to be interested in.

yup except that when you expect a 50-100MHz 1GSps scope to show good fidelity on 1-2ns rise/fall time, then its just ridiculous. not to mention invalid setups to prove a point where in one measurement, ringing (on the falling edge) is much more prominent in the said DSO. here look again... with the right mind we should expect some illusive aliasing (wave superimpose) on the signal packet... signal dis-integrity due to questionable measurement setup.

[tautech]

Having come from a 10 MHz scope prior to my Tek 485, I had to come up with some tricks to figure out how to display things that were beyond the bandwidth.

One approach that always works is to slow down the clock.  Get the system to work and then see what happens when the clock is restored. Does it still work?
.................

This.

[MK14]

I DON'T agree that the analogue scope is so useful for signal integrity (as regards rare phenomenon). Because there can be occasional and super rare events such as glitches/transients/metastability etc which can flip bits (to incorrect states), when they occur. But may be very difficult to detect with analogue (non-storage tube and/or digital) oscilloscopes.

With a digital scope (with sufficiently powerful enough capabilities), it can be triggered (one-shot), when the MCU (or FPGA or whatever), detects bit errors, bit collisions, etc.
These may be extremely rare (e.g. metastability), and take many hours to occur (trigger).
Nevertheless, these issues need to be sorted, in order for the hardware to work properly, in most cases.

The top MCU (that the OP seems to be using), can go to a claimed 4000 MIP's. I don't know its clock frequency, but that COULD be 250 pico seconds (4 GHz). So I can imagine the OP, with a signal mostly at 0, but at 1 for just 250 pico seconds, with him trying to display it on a 50 MHz oscilloscope. Then creating another thread, complaining about why he can't see his 250 pico second signal, on his borrowed 50 MHz oscilloscope.

tl;dr
There are some very good reasons why, analogue oscilloscopes (brand new), have partly or fully disappeared from the market place.

[tggzzz]

yup except that when you expect a 50-100MHz 1GSps scope to show good fidelity on 1-2ns rise/fall time, then its just ridiculous.

It would indeed be ridiculous.

But for reasons best known to yourself, you have chosen to ignore paragraph 4 in the first post "The first point...". Hence your point is a strawman argument.

not to mention invalid setups to prove a point where in one measurement, ringing (on the falling edge) is much more prominent in the said DSO. here look again... with the right mind we should expect some illusive aliasing (wave superimpose) on the signal packet... signal dis-integrity due to questionable measurement setup.

That's incoherent technobabble; clearly something has been lost in the translation.

[rstofer]

Now, there's something that hasn't yet been mentioned but which is quite important.  And that is that it's probably not an accident that entry level microcontrollers are relatively slow.

<snip> 

For these reasons, I don't expect beginner territory to change all that radically even if microcontrollers can be faster.

We already have uCs that are very much faster than the Arduino.  The Blackfin is about 600 MHz and it isn't even in the running for FAST.  But you're right, they aren't for beginners.  The learning curve is high and steep.

What the Arduino has going for it (as the Basic Stamp had before the Arduino came along) is reasonable performance and a tremendous support group.  Programming the device is made easy by the library code and there are thousands of example projects on the Internet (no, I didn't count them!).  OTOH, the Parallax Basic Stamp is probably the best documented uC ever sold.  Parallax has wonderful documentation.

Experienced users kind of chuckle at Arduino users but that Arduino is a heck of a lot faster than the IBM 1130 I programmed back in '70.  And it was state of the art for entry level minicomputers.


Unless there is a major shift in thinking, I see the Arduino as the beginner's CPU of choice for a very long time.