The Logic Meter

[rea5245]

I've made a new type of test instrument: the logic meter. It's sort of a mash-up between a logic analyzer and a multimeter. I've posted the design and source code on GitHub in the hope that someone will take this idea and turn it into a commercial product.

I've made a video that demos the product and explains the design:

[DEV001]

This is pretty cool project and it looks like it could be a potential 'portable' Bus Pirate type of device for makers. 


Edit: I found your Github in the video description: https://github.com/galacticstudios/Logic-Meter

[Fraser]

Rea5245,

That is a really interesting unit that you have designed. Would you believe I have been searching for a handheld unit that can auto detect RS232 baud and display the data without having to mess around with a computer or bulky RS232 Protocol analyser. Your unit looks to fulfil my need well and has the added bonus of the other functionality.

I am looking for a PIC32MZ2048EFH064 dev board to use as the basis of building your design but wanted to check that you are not able to offer your populated or unpopulated PCB upon request ? A working, programmed PCB would be ideal as then I would only need to build the casing and add the display etc.

Thank you for sharing your design with us and I will follow any further developments with interest 

Fraser
United Kingdom

[rea5245]

Hi Fraser,

Do you mean RS232 or UART? RS232, of course, has voltage levels that could be dangerous to PIC32s.

I have a small number of partially populated boards (basically, I had JLCPCB assemble the tiniest, hardest to solder components - although the PIC32 itself is not in their parts store, so it's not assembled). One thing to know is that board uses a Tag-Connect connector for interfacing to the Microchip ICSP (https://www.tag-connect.com/product-category/products/cables/mcp-pkt).

I'd be willing to sell you a board. Contact me through my website, galacticstudios.org/contact.

- Bob

[Fraser]

Yes, I should have said UART. I would add a MAX232 level changer for true RS232 levels.

The partially assembled PCB sounds perfect I will be in touch via your web site 

Fraser

[ledtester]

I just discovered this:

https://github.com/michar71/Open-DSO-150

-- an open source firmware for the DSO150 hand-held oscilloscope.

The firmware adds three digital channels that it can display in addition to the analog channel.

So... maybe you can incorporate your ideas into this firmware. Or, completely replace the firmware with your own. The DSO150 pretty much has all of the user interface elements you need -- screen, buttons, rotary encoder.

[Alex Eisenhut]

Good job but I'm not so sure it's that new.

HP Logic Dart was made 25 years ago.

https://youtu.be/rXDwaYdC5ng?t=136

I've always wanted one and never understood why it's not a popular instrument category.

[Electro Fan]

Cool.

Congrats!

Sort of a LA + DMM + Function Generator + Power Supply.  It’s not quite an Analog Discovery (although potentially in time the firmware/software might go further in that direction) but maybe it’s a cousin of the AD within a more handheld-oriented form factor/enclosure. 

It’s maybe not so much a solution in search of a problem as it is a new idea in search of a name that helps define it as a leader in a yet to be designated category.  Reaching your objective of seeing it commercialized might depend on how well it can be named in a way that helps convey the functionality, the leadership it represents in the category, and of course the eventual selling price.

One question is whether it gets commercialized as something proprietary or open source (hardware and/or software).  There is a 2 million view thread on a $20 LCR ESR Transistor Checker.  Some of what drives the interest, I think, is that there is a desire for not only a cost effective multi-function tool but also a tool that the user community can participate in customizing, adapting, and extending as well as simply using.

Yet another thought is that PICs are popular but so are Atmegas/Arduinos.  You have a notable foundation built on the PIC but might there an even bigger addressable market if it was built on some Arduino variant?  Or maybe there are some cost or other reasons to stick with the PIC?  Yogi Berra said unless you know where you are going you could wind up somewhere else.

In the end it might depend on how well / how much you are able to guide it while unleashing it.

You might have a small tiger by the tail

Good luck with the tiger training and taming!!

[gnuarm]

I would be interested in commercializing this device, but it is exactly the sort of thing that once a market is created by and for it, would be pirated by a far east clone.  It was fun for you because it was about exploring the capabilities of a basic technology to see just what hoops you could make it jump through.  Commercialization would be about minimizing costs to the bone and struggling to stay ahead of the imitators. 

I would be concerned that after putting in time and money, just when sales start to take off, the item is noticed by the clone makers and sold for a fraction of the price (even if they don't work as well) destroying any profits on this unit.  It's just the way the market is I think.  I expect that is why none of the test equipment makers have invested in inventing such a device.  It's just too low end to be a commercial success. 

Now watch someone run with the idea, show up on a crowdsourcing site and become a millionaire!

I wonder if there is something which could be used as a logo that would be so offensive to those who clone a device that they would not copy?  So any clone would at least not be a trademark rip off. 

[Kean]

Good job but I'm not so sure it's that new.

HP Logic Dart was made 25 years ago.

https://youtu.be/rXDwaYdC5ng?t=136

I've always wanted one and never understood why it's not a popular instrument category.

I have a HP Logic Dart and it is my favourite bit of kit, followed closely by the BM235.  It is a nice combination of low voltage multimeter, logic probe, and 3 channel (very simple) logic/timing analyser.  Considering the design it is a pity they didn't incorporate a few more features.

I'm not too sure the LCD on mine will last much longer though as I just noticed yesterday that it is badly discoloured in the centre and is losing contrast.  It has been like this for a while, but is getting noticeably worse.  I wonder if there is a compatible LCD I can salvage from another HP calculator.  It also chews through batteries faster than any other hand-held device of mine.

There are a few posts on here about the Logic Dart (E2310A), so at least 3 or 4 other members have them.

[Fraser]

I own six LogicDarts 

I bought brand new units that HP disposed of at ‘end of support’ plus some that were lightly used. The challenge with buying LogicDarts is the test leads. If they are not included they are very hard to find and expensive when you do. I was firtunate enough to to find several sets of the leads plus complete brand new lead sets that included the browser stylus    Why did I buy so many when I use only one ? Well they were neat and I like them 

I have a DVD of a presentation by one of the design team who created the LogicDart. It is a fascinating story behind the units development and it is a joint effort by two very different product development teams within HP. The test and measurement team and the calculator team. Sadly the product was not really a financial success. It was too specialist and too expensive.

The LogicDart is a very nice piece of kit but it has its limitations. No LCD backlight and logic waveform display only with no protocol decoders, not even UART serial. Protocol decoders were probably too much to expect for this era of unit though.

The LogicMeter is different to the LogicDart as it offers very different features. A LogicDart format LogicMeter woukd be a thing of beauty though 

My post on making DIY LogicDart probes.....

https://www.eevblog.com/forum/projects/hp-e2310a-logicdart-probes-how-to-build-your-own-probes/

Fraser

[Alex Eisenhut]

This isn't helping my TE envy here. I still don't understand why the LogicDart failed in the market.

I'd love something like it when tooling around my collection of failed 8-bit stuff. The old logic probe sometimes just isn't enough, and a scope is too much.

[ledtester]

What was the price of the Logic Dart? This discussion suggests it was $800:

https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv013.cgi?read=40013

[Electro Fan]

I own six LogicDarts 

If 19 is par for oscilloscopes maybe 6 is par for LogicDarts.

[helius]

I wonder if there is something which could be used as a logo that would be so offensive to those who clone a device that they would not copy?  So any clone would at least not be a trademark rip off. 

Base it on the flag of East Turkistan?

I'm not too sure the LCD on mine will last much longer though as I just noticed yesterday that it is badly discoloured in the centre and is losing contrast.  It has been like this for a while, but is getting noticeably worse.  I wonder if there is a compatible LCD I can salvage from another HP calculator.

Dying LCDs can be caused by bad capacitors on the LCD drivers, or by delaminating polarizer films. If the display works correctly (refreshes okay and no dead lines) but is just hard to see, it's usually the polarizer.

[Kean]

Dying LCDs can be caused by bad capacitors on the LCD drivers, or by delaminating polarizer films. If the display works correctly (refreshes okay and no dead lines) but is just hard to see, it's usually the polarizer.

Aha, excellent point!
You can see a dark spot even when turned off.  The display does work otherwise, and under bright light and at the right angle you might not even notice a problem.
I'll dig out some polarising film and try see how the LCD is assembled.  It has got to the point where it isn't fun to use so I am willing to take the risk to open it up.

[gnuarm]

Seems to me you might be able to ditch nearly all of the hardware and develop a user interface just as good by ditching the entire case, switch and LCD and putting it on a cell or tablet.  While this device was designed taking advantage of the capabilities of the CPU in question, I'd be willing to bet you could get 90% of that out of the higher end processor in mobile devices.  If needed, the dongle that is needed to bring out the I/Os can include the MCU from this design while the UI which is most of the design can be the mobile device.  Why reinvent the wheel in that regard with a lesser screen and more awkward controls?

[Electro Fan]

Seems to me you might be able to ditch nearly all of the hardware and develop a user interface just as good by ditching the entire case, switch and LCD and putting it on a cell or tablet.  While this device was designed taking advantage of the capabilities of the CPU in question, I'd be willing to bet you could get 90% of that out of the higher end processor in mobile devices.  If needed, the dongle that is needed to bring out the I/Os can include the MCU from this design while the UI which is most of the design can be the mobile device.  Why reinvent the wheel in that regard with a lesser screen and more awkward controls?

I think this raises lots of good ideas and questions. 

In IT we have seen some utility delivered from servers and some from “appliances”.  The tradeoffs include flexibility and functionality, ease of implementation, ease of use, size, upgradability, reliability, availability, serviceability, costs (including NRE) and price, plus strategy (are you trying to create barriers to competitive entry to protect investment and maximize investor ROI or are you betting on open source adoption of hw and sw, or some combination), etc. etc.

In barcode scanners we had/have dedicated handheld scanners and sleds that fit on phones.  Likely there are (maybe many) other good examples of design tradeoffs.

No doubt the discussion cascades into much of Test Equipment and especially user interfaces.  Do you prefer knobs and buttons on a traditional oscilloscope or GUIs on a computer or some combination? 

The product (and the concept of the product) in this thread could go in a lot of directions depending on the vision and motivations driving the vision.

[wizard69]

This is really cool.   It might not have the mix of functions I would want but even so this obviously took a lot of work to get this level of functionality.   On the other hand it has enough functionality I might be tempted at the right price.

In any event some suggestions if you or anybody else should decide to go forward with this unit:

• Interfacing to RS232 should be on its own port.   Not just for voltage tolerance but also because there would likely be a cable already configured for the IBM 9 pin port.    So a DB-9 for the port monitor.   Half the trick in working with RS232 is having the right cable.
• Ideally the RS232 support could be run in background continuously.   I know if we are not careful you could end up with Linux running on this machine.   However the point here is that it might be important to catch data coming from the port while you are doing something else.
• 3 bits really isn't enough logic analyzer wise, 8 bits would be ideal.
• The servo and PWM functions are fantastic to have in a handheld device.   I'd almost would want to say that the servo function needs to run on its own, maybe through a dedicated port.   This gets back to the problem of blowing up the software to the point you need to install Linux or similar OS.    In any event the right processor choice would mean a servo output with near zero performance impact even if running concurrently with other features. 
• One function that might well be worth implementing is the detection of illegal transitions from quadrature encoders.   An surprising number of drives or controllers, still will not catch illegal transitions properly thus a device that can do so for you would be handy.   Being able to count and handle direction would be nice too.
• Being able to read the voltages on pins may have some use.    So a simple DC voltmeter functionality would be nice.
• At risk of completely bloating the device, function generator ability would be good also
• This unit cries out for color.

In any event this is a fantastic bit of prototyping.   

[fcb]

Nice project - obviously put alot of time and effort into it.

You might be better making different niche versions, perhaps an automotive protocol version, RC modeller version, etc.. - but it looks like you aren't looking to directly commercialise the unit?  If you are, then perhaps prove the market by offering a simple kit on Tindie or doing a simple Kickstarter?

[wizard69]

Seems to me you might be able to ditch nearly all of the hardware and develop a user interface just as good by ditching the entire case, switch and LCD and putting it on a cell or tablet.

This is a good idea from the standpoint of UI but most tablets do not have the I/O capability.    You would need a dongle and that would mean carrying a dongle around.   On the flip side tablets and even some cell phones can do pretty fast USB-C communications.   If you go with a fast USB-C connection, and ignore most of the cell phones and tablets available, this could be a good idea.

While this device was designed taking advantage of the capabilities of the CPU in question, I'd be willing to bet you could get 90% of that out of the higher end processor in mobile devices.  If needed, the dongle that is needed to bring out the I/Os can include the MCU from this design

You would certainly need a dongle.   Most of the devices you have described (cell or tablet) only have one USB port for communications so you would almost certainly need a dongle.   In the end you would have something like the already existing logic analyzer boards out there.   That isn't a bad thing especially if the dongle can be delivered in a form factor compatible with a cell phone.

while the UI which is most of the design can be the mobile device.  Why reinvent the wheel in that regard with a lesser screen and more awkward controls?

More so COLOR!   There are two ways to look at this though, a simple monochrome screen is cheap and doesn't demand much from the processor.   On the other hand a cell phone will be supported with great developer tools and a robust GUI tool kit.

I'm kinda torn here!   On one hand I completely agree with your point with respect to cell or tablet tech.   On the other hand the suggestion to narrow the device functionality, for example target RC hobbyist, makes a lot of sense to me.

If you target one user group you can eliminate much of the software complexity, refine your custom GUI and control costs.  That is one side of my mine but then the thought of a fully scriptable environment with Micro Python just popped into my head.   If you work with a lot of RS232 devices you will run into situation where you can't just copy a file to port.   You may need to set the device for communications or you may need to address specific resources on the device.   A script can make it much easier to configure a device to the specific use case in an industrial situation.   But this goes back to your point with regards to a cell or tablet as you would have huge processing capability there.