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yyrkoon

Logic Analyzers

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So, I have to bit bang a special UART protocol . . . some of you may know this already. Anyhow I figure to make life much simpler, I should probably buy a suitable logic analyzer. The thing is, I have no idea what I should get. I do not want to spend a lot of money. . . sub $100 would be great, sub $50 would be even better. So long as the hardware I'm buying lasts a reasonable amount of time for the cost. Second, I would very much like software that helps me with signal / protocol decoding.

 

Passed the above stuff I mentioned, I have no clue what I would need . . .

 

So which logic analyzer do you use, and why ? What are things I need to look out for ?

 

Additionally, I was checking out this video, and this software. plus hardware looks like it'd be exactly what I'd need. Thoughts ?

 

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I have and use a Saleae logic-8, and have a logic-8pro at work. The lowest end is logic-4 at about $110. For what you are looking at (sub-100KHz) the logic-4 would do well as the sample rate is 12MHz. The logic-8 is 100MHz sample, which is reasonable to about 10MHz systems. There software has several protocol analyzers (I2C, SPI, RS232/standard serial, USB, and about 20 others) and I think it is possible to write your own. I have nothing but good things to say about the unit, and would only give the standard cautions that the units are most useful on a laptop running on battery power to avoid ground issues. A number of the far east import units are near clones, but I can not speak for the quality of them. (one I was looking at had a link to Saleae for the software. I thought that was a bit.... scummy)

 

The reason I went for this is that the reviews were good, the sample rate was sufficient for most of what I need, low V to 5V logic compatible, protocol decoders for things I need are not extra cost, and the software is a good match for what I have used in standalone units for many common features. You can pull the software and play with it without the unit. If there is no unit on the computer, the software fakes it for you for demo.

 

Learning curve is good enough that I have had students using it to debug I2C and SPI in less than 15 minutes. Not experienced students, but first time with anything more involved than blink an LED level students.

 

Edit: watched the video you linked. Looks like a Saleae clone. I don't like the plastic case (shielding issues), but at sub-mhz it is likely not a problem. I haven't used the software he uses. I have a windows machine for such things (due to Autodesk, oscilloscope remote UI, and the microscope cameras), so it isn't a hassle.

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@@enl @@zeke @@Fred

 

I want to avoid Saleae period. I was watching a Ganssel video on youtube, Where he's pitching their logic analyzer vigorously. So, I go check it out, which is their 8 channel pro model. So it can't cost that much right ? WRONG! $450-$550 USD, for what ? $20-$30 worth of parts ? Then some software I'd probably never use.

 

The clones ? Yeah I don't know. Maybe, so long as the sigrok software is supported. But the clones are top dollar clones too . . . more than $100 for an 8 channel pro, clone.

 

Do I really need something that is super fast ? I could see maybe for SPI, but I'm not sure I'd need to be debugging / analyzing SPI any time soon. In my mind, if the device worked decent, and did not have any issues. It's worth the $34USD just for this one project. Or better yet all my UART projects.

 

The only real issue I have with the one listed in that video. Is shipping time. You can order it on amazon for $34 shipped, and get it by Dec 6-20 . . . guess where it's coming from . ..

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One thing I am unsure of. How is buffering handled, and how is that important between low-cost, to high-cost logic analyzers ? So like the guy in the video only did 1M samples, for 1Mhz, and 2Mhz. Why though ? Is this an analyzer hardware issue ?

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I was thinking more of the <$10 eight channel clones. Definitely good enough for some UART debugging.

 

I'm in the UK but found UK sellers shifting them from a UK warehouse. Obviously they're all from Shenzhen originally. (Hmmm. Just searched and there seems to be less around than there used to be, and all seem to ship from China now.)

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@@yyrkoon

 

I have the genuine Saleae and a chinese counterfeit. Their hardware and software is solid. The counterfeit ... well, you get what you pay for.

 

FYI, they are under pressure by the far east counterfeiters.  

 

Rest assured that the company is filled with good guys and their products are Made in the USA.

 

There's no sense in getting worked up about it. It isn't worth the stress.

 

Just switch off your emotions and select a logic analyzer based on its abilities.

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@yyrkoon

They are not cheap, but keep in mind that they developed the software, and, unlike some of the clones (by the magic of google) actually perform as advertised

 

I may be biased, having spent several thousand dollars for significantly less performance during the present millennium for a dedicated device, but I see it as a real deal.

 

With the USB units, buffering is a concern, but none of them (as far as I can tell) are over endowed with memory. They need a USB channel that can suck up data and a host that can do something with it. I have had no issues at 500MHz with a saleae pro on a netbook, but I am not streaming netflix when I am using it. You are looking at low speed UART work, and I would bet a ZX81, or bottom end saleae clone, would be capable of dealing with it.

 

If you are in a time pinch, at those speeds, an MSP430G can split the bits and ram them up the USB line from a launchpad. A 13$ msp432 can do a lot better than that.

 

Given what you are looking at, you are likely to need to write your own protocol analyzer, or see if one is available for a standard device. The Saleae has the advantage of a reasonable dev environment for rolling your own protocol analyzer.

 

The only things showing up in a quick google search that do DALI are pretty far up in price and are locked up against building your own.

 

If it were me, and a deadline was up, I'd call saleae and grab the logic-4 or logic-8 on fast shipping.

 

If $100 is a killer, then you already blew too much time on the project.

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@@Fred @@zeke @@enl

 

I went ahead and ordered the one from the video off Amazon. As for cost and blowing my budget . . . the money for this is coming out of my own pocket.  For something I may never even use again. You guys may have an actual use for the Saleae products, that's fine, I get that. But, I don't So spending ~$500 is really not acceptable.

 

It's kind of like the ole serial debug cable "debate" for the beaglebone black. You can buy from a well known "trusted" name brand FTDI for $20 usd. *Or* You can buy a Prolific PL2303HX Cable that performs the exact same functionality for less than 1/10th the cost. Granted, I'm all for dealing with trusted name brands. But not just for the sake of spending more money. There has to be a compelling reason.

 

Anyway, it won't be here for around a month . . . I will try to remember to relate to everyone what I personally feel about this once I get some serious time using it.

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Just to be 100% clear on why I don't want a Saleae. I can't justify the cost right now. I haven't even billed my client since I've started "officially" doing work for him - Yet. E.G I'm a contractor. So funds right at this moment for me, are a bit tight. The gadget freek of my personality however does want the best top of the line Saleae logic analyzer imaginable . . . But as I posted in a previous post. I'm not even sure how much I'll use one right now . . .

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@@yyrkoon

 

These days, I rarely use my Saleae Logic but I know that it is within an arm's reach if I need it.

 

I has saved me countless hours of debugging when working on a brand new sensor or when developing a brand new device driver.

 

As a Contractor, your value will increase to your clients therefore you ought to be charging more for your services. Tools and software that are needed for the job ought to be factored into your agreement with your client so that they are covered. 

 

Keep this in mind. Your client will take your hard work and turn around and make 100x his investment cost when he sells it to his clients.

 

You are worth every penny your charge!

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If it helps any. The Logic Analyzer I purchased seems to be a clone of Saleae's 24Mhz 8 channel Logic Analyzer. It even supposedly runs their software. According to what I understand from watching Matt Ranostay's sigrok youtube video. It'll handle everything I'd ever want to do, and if I needed something "more", I'd have to probably go to the super high end range Logic Analyzer. Apparently many people were using this clone, or one similar to it back in 2013 during the early sigrok days.

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Oh, right.

 

Additionally for the next month. I'll have to suffer through setting up some sort of test contraption. In order to develop software. As it's likely my client won't want to sit still for a month. Granted this is not the only aspect of the project I'm working on, just one he deems the most important.

 

So what I'll probably do is setup the launchpad to take the normal 9600 baud emulator UART, and use a prolific cable on the software UART back into windows to verify as well as I can. This way, I can keep a common ground between the two sides through using the same USB hub. But this wont really allow me to verify this funky protocol I have to whip up. As I do not think that Windows, or even Linux can handle more than 8 data bits.

 

I had originally thought about powering the launchpad through a beaglebone from the P9 header ( P9.1-P9.8 ) are all power related pins. GND 3v3 5v, etc. But I do not think I could keep a common ground with that setup, so would risk blowing a few GPIO's if I did not remember to pull the USB serial adapter out of the hub before power cycling.

 

Then, the DALI bus can run 9.5v to 22v DC to power the bus. Our bus supply I believe runs at 20v DC, and the Logic Analyzer I bought I think can only tolerate up to 13v or so. So looks like I'll have to use my buddies Hantek USB scope to read on the DALI bus side. Which with the stock application does not offer any logic analyzer functionality. . .

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So,  I found the software through another seller. This is an USBSee AX clone, and . . .

C:\Users\William\Desktop\SKU269906-USBee-Test-Pod-Software-(64-bit)\software\AXPRO-NEW
? dir
. . .

07/18/2011  12:21 AM    <DIR>          .
07/18/2011  12:21 AM    <DIR>          ..
07/18/2011  12:21 AM    <DIR>          ax keygen
07/18/2011  12:21 AM    <DIR>          axsw-Usbee Suite
07/18/2011  12:21 AM    <DIR>          usbeesuitesw-USBee Suite Standard Software

Looks shady. Maybe I should report these people to Amazon ?

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