Everything You Need To Know About Logic Probes

We just spent the last hour watching a video, embedded below, that is the most comprehensive treasure trove of information regarding a subject that we should all know more about — sniffing logic signals. Sure, it’s a long video, but [Joel] of [OpenTechLab] leaves no stone unturned.

At the center of the video is the open-source sigrok logic capture and analyzer. It’s great because it supports a wide variety of dirt cheap hardware platforms, including the Salae logic and its clones. Logic is where it shines, but it’ll even log data from certain scopes, multimeters, power supplies, and more. Not only can sigrok decode raw voltages into bits, but it can interpret the bits as well using protocol decoder plugins written in Python. What this all means is that someday, it will decode everything. For free.

[Joel] knows a thing or two about sigrok because he started the incredibly slick PulseView GUI project for it, but that doesn’t stop him from walking you through the command-line interface, which is really useful for automated data capture and analysis, if that’s your sort of thing. Both are worth knowing.

But it’s actually the hardware details where this video shines. He breaks down all of the logic probes on his bench, points out their design pros and cons, and uses that basis to explain just what kind of performance you can expect for $20 or so. You’ll walk away with an in-depth understanding of the whole toolchain, from grabber probes to GUIs.
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Salvaged LCD screen hacking

You can find all kinds of LCD screens in broken electronics. But it’s often a chore to figure out how they are controlled if you don’t have a working device that can be used to sniff the communications protocol. [Justin] grabbed this character LCD screen from an old Brother printer and decided to see if he could reuse it in his own projects. Luckily the driver card still worked so he patched into the LCD’s control lines and sniffed the signals when the printer is powered on.

He used the OpenBench Logic Sniffer for this project. It easily captured the data, and also provided analysis tools. The SPI analyzer managed to decode the command signals and message of “Please wait” that pops up at power up. After a bit of folly with the pin out of the display, he is now able to control it thanks to an Arduino library which he wrote. Check out the demo after the break to seem him scrolling through a bunch of different functions for the device.

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IM-ME USB dongle hacking

This circuit board is from the USB dongle of a Girl Tech IM-ME. [Joby Taffey] took it apart and poked around to learn its secrets. These dongles come along with the pink pager that has become a popular low-cost hacking platform. But we haven’t seen much done with the dongle itself up until now.

[Joby] used the OpenBench Logic Sniffer to gain some insight on what’s going on here. The board has two chips on it, a Cypress CY7C63803 USB microcontroller which talks to the computer over USB and also communicates over SPI with a Chipcon CC1110 SoC radio. It looks like reprogramming the Cypress chip is a no-go, so he went to work on the CC1110. The inter-chip communications data that he acquired by sniffing the SPI lines gave him all he needed to reimplement the protocol using his own firmware. As a proof of concept he to reflashed the CC1110 and can now send and receive arbitrary commands from the dongle. There’s a tiny video after the break showing a script on the computer turning the dongle’s LED on and off.

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Open source logic analyzer

Hackaday alum [Ian Lesnet] has been working in cahoots with a dedicated team of developers to produce the OpenBench Logic Sniffer. This caseless logic analyzer can operate at 100MHz and sample 32 channels at once. Better yet, a digital oscilloscope add-on is in the works. The pre-order comes in at $45, that’s a lot of functionality for just a few greenbacks. We’ve embedded a demo video after the break that details installing and using this device under Ubuntu.

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