Digilent Digital Discovery Logic Analyzer

[Housedad]

This Thread is about the New Digilent Digital Discovery Logic analyzer.  The product announcement was on March 17th.  I have one on order and it will be in on Thursday, so I'm jumping the gun by a few days.  Hopefully we can set up what to do to review it in that time.  Since this is one of the first 100 purchases, they are including the High speed adapter and wires, so it will be complete with all options.

I figure this can be a review/learning experience.  I have limited knowledge in modern electronics and zero experience with a logic analyzer,  and will be seeking input from the group about finding out what this thing can and cannot do.  So, if anyone is interested, I can make some simple circuits and put it to the test.  i have just put my electronics bench together, so there is some, but not a lot to work with.  i don't mind buying parts to make test circuits.



With all that in mind, here is the webpage at Digilent.:

http://store.digilentinc.com/digital-discovery-portable-logic-analyzer-and-digital-pattern-generator/

As far as what is available that I can find on their site, the doc look pretty slim.  It initially seems to be marketed not to the beginner, like the Analog discovery, but to those with  working knowledge of using a analyzer.  Even with what they have, I am already lost on part of it.  Maybe we can find a procedure to follow to test it all out.


Features:

9.1. Logic Analyzer

    24 high-speed input channels (DIN0…23), accessible through one 2×16 connector, used with the Logic Analyzer in Waveforms (560k?||10pF)
    16 digital I/Os (DIO24…39) arranged in two Pmod-style (2×6) connectors, used with the Logic Analyzer in Waveforms 1)
    800MSps input sample rate when using maximum 8 inputs (and the High Speed Adapter), 400 MSps with maximum 16 inputs (with the High Speed Adapter), 200MSps and lower with maximum 32 inputs 2)
    User programmable input and output LVCMOS voltage levels from 1.2V to 3.3V 3) (5V compatible 4) )
    100MHz signal input bandwidth
    2Gbit DDR3 acquisition buffer for Logic Analyzer
    Multiple trigger options including pin change, bus pattern, etc 5)
    Digital Bus Analyzers (SPI, I²C, UART, Parallel)

9.2. Multi-purpose Digital I/O

    16 digital I/Os arranged in two Pmod-style (2×6) connectors.
    Each of the 16 pins can be configured for input (Logic analyzer) or set as output 6).
    Algorithmic pattern generator (no buffers used) 7)
    Custom pattern buffer/ch.: 32Ksamples
    ROM Logic for implementing user defined Boolean functions and State Machines
    Bus Protocol Controllers (SPI, UART, I²C)
    100MSps max. output sample rate (50MHz maximum output frequency).
    Automatic or manual strength and slew settings for outputs.
    User programmable logic I/O levels from 1.2V to 3.3V (5V compatible) 9),10).

9.3. Other features

    USB bus powered
    User power supplies, 1.2V to 3.3V, available in the two Pmod-style connectors (100mA max)
    Twisted wire high-speed cable option for input channels to insure signal integrity
    Free Waveforms 2015 software runs on Windows, MacOS, and Linux
    Cross-triggering between Logic Analyzer, Pattern Generator or external trigger
    Data file import/export using standard formats
    80X80X25mm, 80g (without accessories)
    includes: USB cable, fly-wire accessory

[rstofer]

I have had mine for a couple of weeks (early adopter, I guess). I ordered on March 17th...

I used the pattern generator to generate a counter and read it back with the logic analyzer.  Worked well.

At the moment, I don't have a project for it.  I just bought it because it was shiny!

[Housedad]

Nice!.   I ordered mine on the 29th.   One thing I am thankful for is that I have a DS1054z.  At least I'll be able to try to see what it can do.   There are apparently less than 100 of them out there right now, so it is rather rare.  I take it you got in on the high speed adapter for free deal?    $50 for it is really high, IMO. 

As I was looking around for a logic analyzer, it seemed that the Digital Discovery was the best bang for the buck, Even though it is new and no track record. 

[Housedad]

Egads!   I know Ebay is a rip off a lot of times, but there is someone selling the Digital discovery for $599.  Same price for the Analog Discovery.  He hasn't sold any yet.  Wow.  I guess he's hoping that it's like P.T. Barnum is supposed to have said: "There's a sucker born every minute."

[rstofer]

Nice!.   I ordered mine on the 29th.   One thing I am thankful for is that I have a DS1054z.  At least I'll be able to try to see what it can do.   There are apparently less than 100 of them out there right now, so it is rather rare.  I take it you got in on the high speed adapter for free deal?    $50 for it is really high, IMO. 

Yes, I got the high speed adapter and, yes, I think it is overpriced as well but I think we're overlooking the labor it takes to make up the leads.  The breakout board is meaningless but those leads have a series resistor under the heatshrink. 

It seems to me that Digilent is changing their focus from entry level experimenter products to higher end educational products.  More so since they were bought by National Instruments.  Some of those 'university' boards are expensive for an experimenter.  Maybe not so much for a student because a) they get a huge discount and b) education is supposed to cost money.

Or maybe it's because the underlying FPGAs are more expensive.  Clearly, they are more capable!

Given that the 2 founders are/were university professors, maybe they were always targeting education.  In any event, I have been a customer for a very long time and I like their products a lot.

[rstofer]

One thing I haven't bumped into is the ability to provide an external 'state' clock.  All true logic analyzers have this 'state' capability and it's kind of a big deal.

The Digital Discovery can help overcome this by having a very high sample rate.  But it isn't the same thing...

[helius]

Even when oversampling, you don't really get the functionality of state acquisition with multistate or conditional triggering. You can't say "capture only the first 10 words of a PCI burst read" or whatever using only timing acquisition.

[rstofer]

I definitely agree, not having a 'state' clock is a pretty big deal.  I really want to see the 'next state' after the clock edge.

Nevertheless, it is possible to sample at 800MS/s and for a low speed system (say less than 50 MHz), that may be good enough.  Most toy projects don't have bus speeds over about 10 MHz and often much less.

If we're looking at I2C, for example, we are probably looking at 400 kHz maximum.  SPI is a lot faster but about the fastest I have gone is 25 MHz.  In any event, neither of these protocols include a 'state' clock.

My FPGA logic analyzer does have a 'state' clock up to a max of 100 MHz.  The problem is, it's just another PCB laying on the workbench with a bunch of wires running here and there.  It works but it is kind of awkward.  That and I don't like the Java UI that breaks every time Sun updates Java.

Like everything else, the Digital Discovery has limtations.  I can work around them...

[helius]

We're in agreement; I just wanted to point out that "real" LAs have been much more sophisticated for a very long time.
For example, they let you configure two independent "machines" and assign pins to each, and you could have one machine in state acquisition with the other in timing acquisition, with the first triggering the second. That would let you search for glitches from a specific bus master, for example.

The greatest drawback of the older analyzers (which can be found very cheaply) is the lack of support for serial protocol decoding that most suffer from.

[Maxlor]

I've looked at Digilent's Waveforms 2015 software, which contains a software simulated demo Digital Discovery. With that, I can't find an option to set the acquisition buffers to something other than 8192 samples. How does the real hardware behave here? Can one set custom buffer sizes?

[TK]

@ $199 it is overpriced, there are better options for less money like the Zeroplus LAP-C that can decode over 100 protocols and has timing and state mode.

The Analog Discovery 2 is a completely different instrument: analog + digital, bode plot, function generator, pattern generator...

[hli]

One thing I haven't bumped into is the ability to provide an external 'state' clock.  All true logic analyzers have this 'state' capability and it's kind of a big deal.

This capability was added with version 3.6.8 of the Waveforms software. (Called 'sync capture')

[hli]

I've looked at Digilent's Waveforms 2015 software, which contains a software simulated demo Digital Discovery. With that, I can't find an option to set the acquisition buffers to something other than 8192 samples. How does the real hardware behave here? Can one set custom buffer sizes?

Yes, you can set the number and the size of the buffers. You can actually do that with the demo device too: click on the small gear icon at the top right, this opens additional configuration options.

[Electro Fan]

https://blog.digilentinc.com/analog-discovery-2-vs-digital-discovery-a-battle-of-logic/