Which logic analyzer for beginners?

[Watth]

Hey EEVPeople,
As I'm starting to implement serial communications (I2C and SPI), I'm thinking of buying an entry level USB logic analyzer. 8 ports should be more than enough for me.
I've seen on Aliexpress and Amazon that prices start in a range from 10 to 20 € for what seem to be a generic design. I guess it relies on free softwares, open source for some. I've seen that Sparkfun offers its own branded version.
For a little more money, I've seen the BITMAGIC-BASIC-V1, but as far as I know, it doesn't provide better features.
After that, prices go higher with features I don't think I need.

Do these entry level perform adequatly for hobbyist's use? Are there brands to recommand?
Thanks for reading this message!

[daveho]

The cheap Saleae Logic clones (which I assume is what you're seeing based on the price range you mentioned) work quite well with Sigrok. For the price it's pretty hard to go wrong.

[isometrik]

I have used a cheap Saleae Logic clone at some point, but quickly found out they are very limited (no voltage level adjustment, limited sampling rate, etc).

I ended up buying a DSLogic Plus from DreamSourceLab, and although it's more expensive than what you have budgetted, it's a more serious tool. See https://www.dreamsourcelab.com/product/dslogic-series/ for more details.

The original Saleae Logic 8, Logic 8 Pro, etc. would also offer better characteristics, at a higher price however. See https://www.saleae.com for more details.

[fourfathom]

I've also used the $12 Saleae clone with Sigrok, and it works fine for reasonably slow logic and standard logic levels (I assume, I've only used it for 3.3V logic).  But I eventually wanted to use it on 100 MHz-clocked logic (FPGA) and somewhere above 10 MHz it just couldn't cut it anymore.  So I spent a lot more money and got a DSLogic Pro16 (more than I needed, but that's OK with me).  This definitely does the job.  The DSLogic analyzer comes with "DSView" which appears to be based on Sigrok.

[eugene]

If you happen to have a Raspberry Pi, you can use it as a logic analyzer with piscope. The output is displayed on a pc (Windows or linux) via X11.

notes:

• It's limited to 3.3V logic. If you're using 5V logic then your RPI will likely be destroyed.
• You need to install piscope and pigpio on the RPI.
• You need to install putty and ming if using a Windows machine for display.
• I don't know for sure what the sample rate is, but pigpio defaults to 200kHz, so I would guess that piscope does as well. That limits usable bandwidth to around 50kHz or so.
• If you don't already have a RPI, forget about buying a new one. Supply chain issues have made them impossible to find

[rstofer]

I think the upper limit is 400k bps for I2C so any LA that will sample at 4+ MHz should be adequate.
I'm not sure what the fastest SPI link runs at but 60 MHz wouldn't surprise me.  Any LA that can sample at 1 GHz would be adequate.

In other words, don't run SPI at full speed and plan to probe it with a $10 LA.  The thing is, not many people even try to run it that fast so it's up to the user how much they want to spend of going fast.

The inexpensive LAs are a place to start.  Get one and learn to work with it.  I built the Sump.org LA from a Digilent Spartan 3 Starter Board and it samples at 200 MHz - pretty decent but I was running the FPGA project board at 50 MHz.  Not ideal but it worked ok.

https://www.sump.org/projects/analyzer/

In terms of FPGAs, the Xilinx Vivado tool includes the capability of defining an Internal Logic Analyzer that runs in the same hardware at the same synchronous clock.  This is on the hardware, not simply a simulation.  Debugging FPGAs take a lot more creativity to find logic design errors.

For a CPU, implement single-stepping either by instruction cycle (fetch through execute) or by state clock, preferably both.  Also implement an address breakpoint that stops the state machine when there is an attempt to access a particular location in RAM.  This will let you debug at the source code level, instruction by instruction after you hit the breakpoint.

Before Vivado, I threaded a 32 bit debug bus through all of the components.  It was commented out in all but the component under test.  I needed a way to get signals generated 3 or 4 layers deep out to the pins.

[Watth]

I think the upper limit is 400k bps for I2C so any LA that will sample at 4+ MHz should be adequate.
I'm not sure what the fastest SPI link runs at but 60 MHz wouldn't surprise me.  Any LA that can sample at 1 GHz would be adequate.

In other words, don't run SPI at full speed and plan to probe it with a $10 LA.  The thing is, not many people even try to run it that fast so it's up to the user how much they want to spend of going fast.

I've seen I2C has modes up to 5 MHz with these new fangled FastModePlusProMega™. But I don't plan on using a LA in such fast modes. As for me it's about testing signal from sources I design (and not on existing equipment), I could simply adapt the serial speed a bit slower if needed. Same for SPI.
Some repliers mentioned logic level issues, but I don't think I'll deal with anything other than 3 ~5.5 V. Silly question: if voltage is too high, wouldn't a resistor bridger do the trick?

From what I gathered, this type of cheapo LA is a good start anyway; and it's totally worth the money even if one decides to upgrade later for a more sophisticated and pricey piece of equipment later.

[rpiloverbd]

I think Sparkfun's  USB Logic Analyzer - 24MHz/8-Channel is a good choice for beginners. The price is also reasonable.
https://www.sparkfun.com/products/18627

[rstofer]

Some repliers mentioned logic level issues, but I don't think I'll deal with anything other than 3 ~5.5 V. Silly question: if voltage is too high, wouldn't a resistor bridger do the trick?

In theory but I haven't tried it;

From what I gathered, this type of cheapo LA is a good start anyway; and it's totally worth the money even if one decides to upgrade later for a more sophisticated and pricey piece of equipment later.

I have a couple of ways of cabling up a LA (my sump.org FPGA based, Analog Discovery 2, Digital Discovery) but I still bought one of the cheapos just to play with the software.  It seems to work well.  I'm a little fuzzy at the moment, I don't know if these cheapos have a state clock input.  Having access to the internal clock of the device under test helps synchronize the samples.

[tooki]

The cheap Saleae Logic clones (which I assume is what you're seeing based on the price range you mentioned) work quite well with Sigrok. For the price it's pretty hard to go wrong.

And they also work with the Saleae Logic software, which is very easy to use, making it a great introductory logic analyzer system.

[BBBbbb]

The cheap Saleae Logic clones (which I assume is what you're seeing based on the price range you mentioned) work quite well with Sigrok. For the price it's pretty hard to go wrong.

And they also work with the Saleae Logic software, which is very easy to use, making it a great introductory logic analyzer system.

Do they still? With the 2.xx versions?
2.xx is being actively improved and is a significant upgrade to the 1.xx versions, but I'm not sure those clones can still be made to work with the new SW,
But Sigrok is quite OK even if the clones cannot work with Saleae.

DSLogic seems (on paper) to offer even better performance than Saleae (in the price range), but I don't know anyone who could give me first hand comparison in reality, and DSLogic have been quite an assholes regarding SW development (actually breaking the Sigrok's FOSS license) so that is putting me off a bit from them.

[Watth]

The cheap Saleae Logic clones (which I assume is what you're seeing based on the price range you mentioned) work quite well with Sigrok. For the price it's pretty hard to go wrong.

And they also work with the Saleae Logic software, which is very easy to use, making it a great introductory logic analyzer system.

The Saleae website only features 400+ € devices. I there was a basic LA on which the clones are based, it's not there anymore.

[Gyro]

They were the logic analysers that Saleae started the company with. They were basically the EzUSB application circuit with some input protection diodes and an expensive milled Aluminium case. They are still supported by their S/W (or at least were until recently - I don't know). All versions are on their website anyway. After Version 1.1.18, they did a partial rewrite and went to a lower contrast UI. It then took them a few releases to get the bugs out. In later versions still, they slowly added support for their newer analogue / digital models.

EDIT...

https://youtu.be/7OCPWCdg2ys

[tooki]

The cheap Saleae Logic clones (which I assume is what you're seeing based on the price range you mentioned) work quite well with Sigrok. For the price it's pretty hard to go wrong.

And they also work with the Saleae Logic software, which is very easy to use, making it a great introductory logic analyzer system.

Do they still? With the 2.xx versions?
2.xx is being actively improved and is a significant upgrade to the 1.xx versions, but I'm not sure those clones can still be made to work with the new SW,
But Sigrok is quite OK even if the clones cannot work with Saleae.

At minimum, the clones of the very first Saleae (the digital-only one) do. I have one of those.
Some clones with analog claim to be supported too but I can’t vouch for that.

 

The Saleae website only features 400+ € devices. I there was a basic LA on which the clones are based, it's not there anymore.

Correct, the clones are of discontinued models.