Scope / Logic analyzer for hobbyist/beginner in microcontrollers

[mirage98]

I'm wanting to start tinkering in microcontroller projects (Arduino/Propeller) using I2C/SPI, etc buses.  I'm wondering what the best combination would be for me to do this.  From my reading it looks like a digital scope is best for this work coupled with a logic analyzer.

I'm looking at something that will handle my needs in the ~1000 dollar range.  Does anyone have suggestions?  I don't have to purchase new, and would actually prefer a higher quality used (Tek, etc) unit to a lower end new unit (Rigol). 

Are there any used MSOs that will fit the bill?  Am I better off with a seperate DSO/LA?  Is there a good combination that I can sync the signals when using two seperate units and overlay the two to get the "complete picture?"

Input greatly appreciated!

[alm]

One option is a separate logic analyzer and scope. For logic analyzers, the Saleae logic is a cheap option ($150), it offers eight channels, 24MS/s (if the USB bus is not too busy) and almost unlimited samples. More expensive is the Intronix LogicPort, for $400. It offers 34 channels, 500MS/s, but only 2ksamples memory depth (with RLE). Apart from the limited memory, it's definitely superior, and has much better triggering and adjustable logic thresholds. In my opinion, PC based logic analyzers make a lot of sense, since you want to be able to add protocols or write your own, and a nice big screen makes it easy to scroll through the samples on all those channels. I believe these will give you more bang for buck than the Rigol LA option, although they won't be on the same timebase. Be sure to try out the software before you buy (they all have some sort of demo mode). I wouldn't buy a huge boat anchor logic analyzer, unless I wanted more features than the PC-based instruments can offer. One issue is that you should always get them with the pods, it's often very hard to get these separately. If it's an old analyzer, it might not support modern serial protocols. What good is a logic analyzer that only supports some ancient microprocessor bus?

I don't think Tek made any MSO's that are available for ~$1k used. You might be able to find some HP/Agilent mixed signal scopes used. HP/Agilent used to have a fairly low sample rate (not great for one-shot or irregular signals), but long memory depth, and I believe they were the first to incorporate digital channels in entry-level scopes. I don't have any personal experience with these, but I believe Dave was quite positive about them.

For a used scope, I'm not sure what you should buy instead of the Rigol (I'd consider the GW Instek that has seen some positive comments on this forum, though you may not be able to 'overclock' it for more bandwidth). For well below $1k (leaving room for the logic analyzer), you could get a Tek TDS200 series scope, but I'm not sure if these are actually better than the Rigol DS1052E/1102E (Dave has both, he should be able to tell). I believe the display might be more stable and the measurements work better, I've heard some complaints about the Rigol with that. The Tek TDS400/500 series might be available <$1k (older, but higher end), but watch out for leaky SMT electrolytics, they can destroy circuit board traces, and they all seem to leak without exceptions. HP might have some good options, if you can live with the lower sample rate. I believe the interface on the Lecroy scopes of the past sucked, but don't have any experience with them.

[charliex]

Another vote fot the LogicPort, Even though i have a bunch of different LA's i typically use it because its just simple to use, the software is a breeze and they update fairly frequently.

[Zad]

I don't want to sound over the top, but $1000 for a scope and logic analyser for microcontrollers? WTF? In the words of a bloke called Dave; Get real! You wouldn't (I hope) learn to drive and decide before you got your car that you needed a dynamometer, exhaust gas analyser and laser alignment system. Get your micro, plug it in, play with it! Get it to do stuff.

Sure, a 'scope is useful, but don't get hooked on test equipment. I see a lot of talk recently about RF spectrum analysers, vector network analysers, precision voltmeters and all the rest. I use stuff like that maybe half a dozen times a year on average, it just isn't needed for 99.9% of the stuff people do on here. If stuff won't work, figure out why it won't work using the most powerful test tool ever, YOUR BRAIN. Learn how to do diagnostics. Learn how things work, and how they fail. The vast amount of diagnosis that I do involving a scope is with a single channel 10MHz non-storage scope. Hell, most of the diagnosis can be done with a £4:99 meter. No, I don't wire up lightbulbs and switches for a living.

[NiHaoMike]

An oscilloscope can be extremely useful for troubleshooting communication problems in embedded systems. Logic analyzers are only useful on parallel communication buses and high speed serial links. And an oscilloscope can allow you to catch marginal signal quality problems, but a logic analyzer cannot.

[slburris]

Try looking at the BitScopes if you want a mixed signal oscilloscope:

http://bitscope.com/

All but the ethernet connected one should be under $1000.

Scott

[alm]

8 channel logic analyzer and 40MS/s for $600 is not a good deal in my opinion, unless you really want the MSO. A Rigol/Instek scope (50MHz 1GS/s) plus $150 logic analyzer would be cheaper and have better performance, and you get a real scope.

Logic analyzers are not just for parallel buses. Even just SPI has four wires (with one slave, more with multiple slaves), so unless you have a 4 channel scope, it's hard to monitor just the SPI bus, plus you might monitor another bus at the same time (eg. input + output). Plus the automatic decoding and better triggering is nice, although you could do it by hand or by downloading the data from a digital scope. No argument that you need a scope in addition to a logic analyzer, it won't replace it.

You can do a lot of trouble shooting with just the schematic, a pencil and your brains, but few people will argue against a scope as essential tool for electronics. A logic analyzer is definitely less important (assuming you have a digital scope), but can be very useful for digital design.

[slburris]

Well, if you are looking for an MSO, what are the alternatives?  I see nothing
but grief from people over at rcgroups complaining about the Rigol models
which are scope + LA.  Is there anything cheaper than the BitScope in the
MSO space?

If you take MSO off the table, for $1000 you can get a Rigol digital, a used
100Mhz Tektronix analog, *and* the Intronix LA!

Scott

[slburris]

Well, if you are looking for an MSO, what are the alternatives? 

To answer my own question, how about this MSO for $249?

http://www.linkinstruments.com/mso19.htm

Wading through the specs, ignore the 2Gbit/sec sample rate -- it's really
200Mb/sec.  At least on paper this seems to be a better deal than the bitscope.

Scott

[alm]

Well, if you are looking for an MSO, what are the alternatives? [...]

If you take MSO off the table, for $1000 you can get a Rigol digital, a used
100Mhz Tektronix analog, *and* the Intronix LA!

That would be my recommendation, although you might want to choose something like Instek instead of Rigol, or a used HP/Agilent, Tektronix or Lecroy DSO, depending on what you can find.

To answer my own question, how about this MSO for $249?

Issues apparent from the specs are just one channel, and very limited vertical settings, 50mV/div to 500mV/div. With a 10x probe, this becomes 500mV/div or 5V/div. You need a 1x probe for signals below 1Vp-p or so, and can't go above 40Vp-p. The max. input voltage is +/- 200VDC. Even 240Vrms will probably be close to that limit with a 10x probe, mains with a 1x probe will probably kill it. I think the BitScope is closer to a real scope, although it's way overpriced compared to cheap bench scopes or used scopes. I don't consider this a scope, just a logic analyzer with a bonus analog channel. I didn't try the software, no idea how good or bad that is. They appear to charge $300 for an API to control it from your own software, this is usually provided for free with the hardware. In my opinion, this is squarely in the 'say no to PC-based scopes, a 20MHz analog scope is more useful' camp.

[charliex]

I use my logic analyser about 10 times for every 1 time i use my scope. so it obviously varies on what you're doing.

[Mechatrommer]

$1000! WOW! i could get $300 50MHz Rigol (later modded to 100MHz) $100 no brand but reliable soldering/hot air station, $100 DMM, a pack of 100x LEDs + resistors (for debugging purpose), copper clad PCBs+accessories, ICs, breadboards, op-amps etc etc and save the rest of the money for later multichannel (8 at least @ 50Msamples/s min) if i go advance to multichannels buses. for debugging my pic and atmel spi/i2c and other IO pins, rigol and the LEDs are the one that mostly help.

[logictom]

If you're just starting with micros and electronics in general why not start off small and work your way up?
How about the bus pirate? http://dangerousprototypes.com/docs/Bus_Pirate
$30 will decode serial, spi, i2c and a few others. Once you need to delve deeper then look at logic analysers and oscilloscopes.
Like Shafri said why not spend the difference on the other basic equipment and some stuff to experiment.