USB LA Recommendation? - Page 1
Forum section: electronics / testgear

author: mrm2007
author_rank: Contributor
timestamp: July 01, 2016, 10:40:56 pm
content: Hello guys,Currently , i'm looking for a USB LA. I have the Original Saleae Logic 8 , But it is not suitable for my current application.In My current Application, I have to monitor a SPI bus Lines + 4 more digital lines , which will have around 3 bytes of data (24 bit) every 100 ...120ms on SPI and some data on other 4 lines (Synced with spi clock).SPI Clock is ~1MHz. SPI clock will be off , when there aren't any data. (it will burst out 3 bytes and will be silent until the next 3 bytes).The problem occurs after a few hours (varies between 1 .. 5 hours) and if i want to capture all of that with saleae Logic, the file size will be huge. Anyway ,i tried that (at 4MS/s sampling rate) and the software crashed after ~30 minutes!I need a Logic Analyzer, which can ignore the dead-time between samples (at least in software and/or uses some sort of compression to lower the data rate) or It only triggers by the SPI Clock and/or SS and Rearm Itself for the next trigger ( Like Normal Mode of an oscilloscope).Another problem with the Original Logic 8 is the input impedance . The Circuit that i have to work with is a very low power circuit (Total allowable Power usage is 2.7ma), currently the circuit uses between 2.2ma .. 2.55ma (depends on various conditions) , so the LA shouldn't Load the lines.according to their website new Logic8 & Pro models have 1Mohm input impedance which is perfect, but the old Logic 8 has 100K input impedance, so for each line (3.3V supply) it may consume about 33uA which is not suitable-depends on the line condition ( if all : 8*33uA=~264uA) . So i think the input impedance should be greater than 200K.So these are the requirements :1) input impedance >200K2) Has some sort of data compression or Re-Arm Trigger3) Budget is Less than 500$ USDCurrently i'm looking at ZeroPlus LAP-C (500k Input impedance) and Intronix Logic Port (220K input impedance), but i still don't know if their software can keep the previous samples after receiving the new data (something like a streamer, but updating the screen after each data segment, not waiting for a whole time and updating the screen at the end).I checked the LA1016 (which has 1Gbit onboard Memory , but it's demo works like a saleae (it seems they copied the Saleae GUI or so)- no advanced trigger),DSLogic Pro (same issue).Is there anything that i missed? Is there any USB LA available with something like this fuction that i explained?

author: ian.rees
author_rank: Contributor
timestamp: July 04, 2016, 10:52:05 am
content: Curious to hear what solution you end up with. Are you running the current Saleae software and have you asked them about the crashing issue?Have you looked in to sigrok? Seems they support the original Saleae, and I'd guess are scriptable enough to help with your situation.Regarding the input impedance; how about putting together a buffer circuit on some protoboard?Is the problem apparent externally? In other words - could you record in 30 minute chunks, discarding them until you catch the problem?

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 04, 2016, 03:28:47 pm
content: My Saleae Logic Pro 16 (software version 1.2.9) definitely has compression. I told it to acquire a handful of channels at 500MS/s with nothing connected, it says it has collected 100 billion samples and that it's using a total of 0MB of memory. Windows shows it fluctuating between 105 and 107MB of memory but not increasing even as another 30 billion samples have been taken. I suspect what you're seeing is either a restriction on the older Saleae devices or a software bug. It's probably worth contacting them in any case.I wish the software had segmented memory, but left and right trigger search in combination with data compression has been a workable substitute, although my requirements for long term capture haven't gotten close to yours yet.

author: coppice
author_rank: Super Contributor
timestamp: July 04, 2016, 04:13:27 pm
content: If you are looking for some serious USB protocol analysis you might look at the products from Total Phase -www.totalphase.com. I've never used them, but I've heard good things.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 04, 2016, 04:44:16 pm
content: Here is my Saleae (Logic Pro 16, as before) after recording 4 channels at 500MSa/s for 40 minutes, measuring the distance between a few bursts separated by 36 minutes, without exceeding 100MB of RAM (it was a bit higher by a constant amount during capture). The .logicdata save file is 136kB. Qualitatively, the display and scrolling are still butter smooth, and it's no hassle at all to zoom in until I can see the details of the "bursts" (i.e. the noise from brushing the logic probe against my power supply output).

author: uncle_bob
author_rank: Unknown
timestamp: July 04, 2016, 05:01:02 pm
content: HiYou mention a problem after 1 to 5 hours. How long a capture are you trying to make?If you are trying to log a few months worth of data, a USB device of any sort may not be the right tool to use.Bob

author: Electro Fan
author_rank: Super Contributor
timestamp: July 04, 2016, 06:44:19 pm
content: You can try the Intronix software - full software with some demo files:http://www.pctestinstruments.com/downloads.htm

author: mrm2007
author_rank: Contributor
timestamp: July 05, 2016, 09:57:22 am
content: Hi,First, Thank you everyone for their answers.Quote from: ian.rees on July 04, 2016, 10:52:05 amStill no solution yet. Didn't contacted saleae yet , but i will. i tested with their latest 1.2.x family & 1.1.15.About Sigrok: Yes , they support original Saleae , but their protocol analyzer is very slow compared to saleae , i'll test it capturing data and activating protocol analyzer later and see what happens.Input impedance, i thought about it, but this device is an industrial device and installed in it's place, i can connect the usb LA to my work laptop, but if i want to put a buffer section, it needs power supply , ...etc. So if there is any instrument which eliminates the power supply, i'll be happy.This is my last resort. but i have to log data in 30 minutes or less segments (~6 hours) and after that i have to analyze it, if there is no software crash.Quote from: jjoonathan on July 04, 2016, 03:28:47 pmQuote from: jjoonathan on July 04, 2016, 04:44:16 pmOk, it seems that new saleae pro series has some improvement over the old one. I'll contact them and ask them directly.BTW, Could you please tell your computer specs? my computer is a Panasonic Industrial laptop , so it has not the latest CPU or massive RAM , but i don't see a cpu load on it too.(it doesn't have Anti-virus and firewall ,....etc too) only the required software and tools.I installed linux on my laptop, and will try Saleae for linux and will see what happen. Usually linux is less intrusive and more stable for long runs.Quote from: coppice on July 04, 2016, 04:13:27 pmThere is nothing about USB Protocol Analysis. The only protocol analysis that i need is SPI.Quote from: uncle_bob on July 04, 2016, 05:01:02 pmAccording my knowledge of how this device works and current problem nature, I think that around 6 Hours data logging is enough.Quote from: Electro Fan on July 04, 2016, 06:44:19 pmYes, i saw it and i tried it. the problem with Intronix software is , if you turn-on Repetitive Run to continuously trigger and Re-Arm itself, when a new segment of data comes in , it will replace the old segment of data and discard the old data completely!BTW, I tried many demos of different logic analyzers and i have to say i like the Intronix much more than any other software. Their latest software is dated 2012 , but it works. if they implement a streamer mode in their logic analyzer (Even for low sample-rates like 4~5 MS/s) , i would buy their device immediately!

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 05, 2016, 12:30:45 pm
content: Update on the Logic Pro 16: I left it running overnight, 4x500MS/s channels as before, it took 8.5hrs of samples, still 140MB of RAM while sampling and 105MB when done. Events at the beginning and end are both clearly visible when zoomed out and zooming is completely fluid. My computer has an i7-3820QM CPU (beefy notebook) and 12GB of RAM, Logic uses 22%CPU and 140MB of RAM while sampling 4x500MS/s. It uses 0.6%CPU and 104MB RAM while sampling 4x10MS/s.I've enjoyed hearing about other logic analyzers -- I have to admit I didn't properly shop around before getting the Saleae -- but I'm quite happy to see it perform so well.

author: mrm2007
author_rank: Contributor
timestamp: July 05, 2016, 06:32:35 pm
content: Quote from: jjoonathan on July 05, 2016, 12:30:45 pmHi,Thank you for update. I think the reason that your ram usage is so low , is because all of your channels are steady-state low. No signal change or toggle.I contacted Saleae and they think the reason of software crash (or Hangs) is low memory. According to them , Both old Saleae & new Pro Series use same compression algorithm, so changing device may not help (unless my LA has a problem). They sent me these 2 links :https://www.saleae.com/performancecalculatorhttp://support.saleae.com/hc/en-us/articles/208667536-How-to-take-long-captures-that-can-t-fit-into-memory-at-all-at-once-How-do-I-use-the-Socket-API-1st one is a performance calculator which is estimates your total capture time (according to your computer RAM & used channels, ... ) and the 2nd link is a tutorial to capture very large data.according to their performance calculator, i shouldn't have any problem at least up to ~15 hours (using only my laptop RAM).As i suggested and they confirmed , i should see better performance in linux , So I'll install Linux and check with their software under Linux and see what happens.if the problem still exists , maybe there is something wrong with my LA or my laptop USB Ports.

author: ebclr
author_rank: Super Contributor
timestamp: July 05, 2016, 07:09:08 pm
content: https://world.taobao.com/item/41121707096.htm?spm=a312a.7700714.0.0.UARAGV

author: mrm2007
author_rank: Contributor
timestamp: July 05, 2016, 08:39:44 pm
content: Quote from: ebclr on July 05, 2016, 07:09:08 pmHi,This is available at lower price than taobao @ Seeedstudio website (75$) . i even found it @ 66$, But the problem is their software. In their software they somehow copied saleae interface, but even in demo , i saw glitches and problems and i don't know how it performs in real world. I think DSLogic Pro , even has lower buffer , is a safer bet than this one.