Logic Meter Aims To Make Hobby Electronics Troubleshooting Easier

The basic test instrument suite — a bench power supply, a good multimeter and perhaps an oscilloscope — is extremely flexible, but not exactly “plug and play” when it comes to diagnosing problems with some common hardware setups. A problem with a servo driver, for example, might be easy enough to sort of with a scope, but setting everything up to see what’s going on with the PWM signal takes some time.

There’s got to be a better way to diagnose hobby electronics woes, and if [Bob Alexander] has his way, his “Logic Meter”, or something very close to it, will be the next must-have bench tool. The Logic Meter combines some of the functionality of an oscilloscope and a logic analyzer into a handy instrument that’s as easy to use as a multimeter. The Logic Meter’s probes connect to logic-level signals in a circuit and can be set up to capture or send serial data, either directly to or from a UART or via an SPI bus connection. There are also functions for testing servos and similar devices with a configurable PWM output. [Bob] rounds out the functionality with a GPS simulator and a simple logic analyzer, plus some utility functions.

The beauty part of the Logic Meter is that [Bob] has left where it goes next largely up to the community. He’s got a GitHub repo with details on the PIC32-based hardware, and the video below makes it clear that this is just a jumping-off point to further work that he hopes results in a commercial version of the Logic Meter. That’s a refreshing attitude, and we hope it pays off; from the look of a few of [Bob]’s retrocomputing makeovers, something like the Logic Meter could come in pretty handy.

28 thoughts on “Logic Meter Aims To Make Hobby Electronics Troubleshooting Easier

  1. A great multi-function instrument. With high speed microcontrollers, FPGAs, wireless connectivity and low cost LCDs, I would expect a few similar products to emerge. At the right price, they may even give the traditional multimeter some market competition.

  2. This is freaking AWESOME! WELL DONE!
    It could benefit from a rotary encoder to set values on the display. (servo value, PWM freq.)
    A function generator could be a neat extra feature and a frequency counter.

  3. Here I would actually say that Rigol’s scopes like the 1054Z and the like are fairly competent.
    Since if you want a PWM measurement, then just set the correct trigger level (anywhere within the signal of interest) and then push the horizontal measurement button and then PWM, done…

    Frequency, peak to peak and numerous other common measurements is equally trivially reached.

    And the case is fairly similar on a fair few other scopes.

    But I have to say that a device like this aiming at both providing logic analysis, but also the ability to generate logic signals is an interesting device.

    It would be nice to see it have some scripting and GPIO capability, doesn’t have to be many inputs/outputs, 8 of each goes a long way, though preferably it should have more than 8 for also being able to have a clock in/out and bus state information too, so maybe 12-18 each. (For adequate scripting ability it might though need more buttons on its interface.)

    Another reasonable thing would be if it stated measurements in both time and frequency. (Doing the conversion in one’s head is prone to being an order of a magnitude incorrect if one isn’t careful…) Or time and % for pulse width on PWM signals.

    For general digital signals, it could also be interesting to have it measure pulse length jitter on individual pulses, or be able to statistically bin it over time, since such can be indicative of problems, usually unwanted race conditions of varying lengths. (One of those hard to measure things to be fair, since the problem can be very infrequent…)

    Would also be useful with a simple event counter. And some simple wizard for basic digital signal out. Like simple clock generation, crude “hardcoded” patterns and counters. (With the above mentioned scripting, the sky is the limit, or rather, the scripting ability and performance of the device is the limit. But scripts shouldn’t replace all trivial tasks.)

  4. I like dedicated instruments, and this is a really cool project. In terms of existing similar products Picoscopes are a thing, and I would call them an engineer’s dream for sure, cheap cheap cheap, and really useful.

    1. I have a Bus Pirate too. But I made the Logic Meter because I wanted something that didn’t require a PC. This is far more compact and convenient than a BusPirate+PC. In the field, you don’t have to worry about where you’re going to put the PC. Using it is faster: turn a knob instead of opening a terminal window, choosing the serial port, and typing a bunch of commands.

    1. Well there’s no display on the Glasgow, but that aside it’s the ideal match: it’s like the anything adapter, what I hoped the Bus Pirate would be but in the end wasn’t.

  5. 98% functionality of this device can be replaced by proper software development practices, rest can be done even with a basic Rigol scope. It’s such a shame that embedded software development way too often gets reduced to copy-pasting “sketches” and writing unmaintanable mess where everything has dependencies on everything else. Decades of academic research, at least 15 years of modern Internet as we know it and still, teaching the art of programming ends on language syntax accompanied by using some on-chip peripherals while software architecture, unit testing, functional programming or design patters are not even mentioned.

  6. I’m a bit in doubt about it being a standalone instrument. Because with logic signals you often profit very much from being able to directly read, interpret, format and manipulate them on a computer. Same thing for outputting them (or having the instrument react to signals of the DUT). The problem is just to make this computer interface really easy to use.

    That is why I really like the concept of the Glasgow: https://github.com/GlasgowEmbedded/Glasgow
    and https://www.crowdsupply.com/1bitsquared/glasgow

    You can of course use it on the commandline. But what makes it really powerful is not only the FPGA being able to deal with just about any protocol, but also the software stack that makes it really easy to interact with it directly from a python script.

    See here for a very basic example of what I mean:

    1. I already have devices similar to the Glasgow. But for some tasks, I wanted a small, easy device that does a useful job without a computer attached.

      And I can testify to its usefulness, at least for many things I do.

      1. I wonder if you could drive the Glasgow from something smaller than a computer, but still with a display. Maybe a Teensy 4? If nothing else you could bolt a raspberry pi onto it

        1. To make the Glasgow work fully, it’s concept requires you to be able to build FPGA gateware bitstreams with Yosys and Nextpnr. While this works on a Raspi, a Teensy doesn’t cut it.

          It would be possible to run the Glasgow software on an Android phone or tablet to get what you want. This would require fiddling around with Termux and the access permissions to the USB a bit, so it may require root.

  7. As the microcontroller has a CAN controller, a CAN monitor would be nice.
    Also I2S, which the micro also has. Imagine having the option to generate test signals (sinus, white noise) via I2S. Maybe even SP/DIF coax and optical. Very handy when testing digital audio equipment.

  8. Thinking seems like a good tool along the lines of NanoVNA, tinySA, LCR T-4 and like a Fluke 101 or other cost effective stand alone tools for specific uses.

    Man, saw the Glasgow above and am like… hhhmmm… that’d be an intensely more advanced goal for more options. Really depends on the user requirements. Maybe like a bluetooth keyboard capabilities too?

    Fun project I’m going to keep in mind, crystal clear video regarding also.

  9. Makes me think of a tool that Blondihacks advised me of, which is apparently super useful in especially retro computing: the logic probe. Makes one tone for a “low” level, another for a “high”, and you can learn what your bus traffic should sound like, etc.

  10. Bob this is a great piece of kit with tons of potential, and I can imagine lots of ways to use it. Now I’ve got to make one… along with some of those stove alarms that were featured on HaD a couple years back!

    1. I’ve been thinking something like a borosilicate glass blown whistle to place in between the spout and lid of the Corning Vision 1L amber pot as an alarm for when I’m boiling water or maybe even with the ones that don’t have a spout.

      Ebay and the Goodwill Stores rained those amberwares randomly at a few store on me a few months back. Even scored a pan and a nice smooth surface La Sauge cutting board counter top saver.

      Thinking time to make a trip to the glass blowers.

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