Mis-captured signal transitions shown on the screen of the LA104, with problematic parts circled in red.

When Your Logic Analyzer Can’t Tell Good And Bad Signals Apart

[Avian] has picked up a Miniware LA104 – a small battery-powered logic analyzer with builtin protocol decoders. Such analyzers are handy tools for when you quickly need to see what really is happening with a certain signal, and they’re cheap enough to be sacrificial when it comes to risky repairs. Sadly, he stumbled upon a peculiar problem – the analyzer would show the signal glitching every now and then, even at very low bitrates. Even more surprisingly, the glitches didn’t occur in the signal traces when exported and viewed on a laptop.

A Pulseview window showing that the problem is not present in the exported capturesHe dug into the problem, as [Avian] does. Going through the problem-ridden capture files helped him realize that the glitch would always happen when one of the signal edges would be delayed by a few microseconds relative to other signal edges — a regular occurrence when it comes to digital logic. This seems to stem from compression being used by the FPGA-powered “capture samples and send them” part of the analyzer. This bug only relates to the signal as it’s being displayed on the analyzer’s screen, and turned out that while most of this analyzer’s interface is drawn by the STM32 CPU, the trace drawing part specifically was done by the FPGA using a separate LCD interface.

It would appear Miniware didn’t do enough testing, and it’s impossible to distinguish a good signal from a faulty one when using a LA104 – arguably, the primary function of a logic analyzer. In the best of Miniware traditions, going as far as being hostile to open-source firmware at times, the FPGA bistream source code is proprietary. Thus, this bug is not something we can easily fix ourselves, unless Miniware steps up and releases a gateware update. Until then, if you bought a LA104, you can’t rely on the signal it shows on the screen.

When it comes to Miniware problems, we’ve recently covered a Miniware tweezer repair, requiring a redesign of the shell originally held together with copious amount of glue. At times, it feels like there’s something in common between glue-filled unrepairable gadgets and faulty proprietary firmware. If this bug ruins the LA104 for you, hey, at least you can reflash it to work as an electronics interfacing multitool.

Teaching A Pocket Logic Analyzer (Many) New Tricks

A few years ago, low-cost pocket digital oscilloscopes aimed at the hacker and maker crowd started hitting the market and gained quite a following. While few would consider them to be a replacement for a proper bench scope, they’re cheap and convenient enough that it’s hard to complain. Manufacturers are apparently looking to expand on the concept, as we’re now seeing similarly priced and sized logic analyzers pop up from the usual sources.

[Gabriel Valky] got his hands on a sub-$100 USD model known as the LA104, and decided that the stock software didn’t quite deliver. So he started a project to create a new open source firmware for the affordable gadget that greatly expands its core functionalities. The code has even been ported to a few of those digital oscilloscopes, as it turns out (perhaps unsurprisingly) that they aren’t too far removed internally.

Controlling addressable LEDs with the LA104.

In the video after the break, [Gabriel] shows off some impressive radio tricks by adding a small CC1101 transceiver to the mix. This allows his modified LA104 to scan for and decode popular RF protocols in the 300 – 900 MHz range. His software even allows for the received packets to be modified and re-transmitted, which he demonstrates by pushing a fake temperature signal into a wireless weather station.

But that’s just the beginning. A perusal of the GitHub page for his replacement firmware shows just how many features have already been packed into this project. For example it can be used to control WS2812 LED strips, generate arbitrary PWM signals, log data from temperature sensors, interface with MIDI devices, and scan for I2C devices. Many of these functions can be controlled on the computer by utilizing a modern browser and WebUSB.

The replacement firmware that [Gabriel] has come up with for the LA104 is really an incredible accomplishment, and elevates an already intriguing piece of kit. Being able to pack all of these functions into something small and cheap enough you can toss into a bag is a very compelling prospect for hackers on the go.

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