PulseView

What it is

PulseView is the desktop application of the sigrok project. It talks to hardware through sigrok's driver layer, and the driver for this analyzer is fx2lafw — a generic, open-source driver for a whole family of USB analyzers built on the same silicon.

That is the reason to have it. Logic 2 is friendlier, and it works here through a compatibility with somebody else's product. This one works through a driver that is part of an open-source project, which is a different kind of guarantee.

Getting it

The downloads page on sigrok.org lists nightly builds and release builds for Linux, Windows and macOS. Take a nightly unless you have a reason not to: the releases are old enough that the page says so itself.

On Linux, your distribution may already package it (apt install pulseview and equivalents), which is the least work. On Windows the installer includes what the device needs. On macOS, drag it to Applications and expect one more step.

The macOS step

The sigrok builds are not notarised, so the first launch is refused rather than sandboxed:

Press Done — never Move to Bin — then open System Settings, go to Privacy & Security, and scroll to the Security section. There is a line about pulseview with an Open Anyway button beside it.

Do this for a build you downloaded from sigrok.org yourself, and not on the strength of a link somebody sent you. The warning is doing a real job; you are overriding it because you know where the file came from.

Finding the device

PulseView's connect dialog is four numbered steps, and only two of them matter here.

Pick fx2lafw (generic driver for FX2 based LAs) as the driver, leave the interface on USB, and press Scan for devices. The analyzer comes back as Saleae Logic with 8 channels. Select it and press OK.

The name is not a mistake and it is not a warning about a counterfeit. It is the profile inside fx2lafw that matched, and eight channels is exactly what you have.

Capturing

Set the sample rate and the sample count in the toolbar, press Run, and make the board do the thing.

Two settings people leave wrong. The rate should come from the bus rather than the top of the list — see samples per bit. And the sample count is a length, not a quality: a hundred million samples at 24 MS/s is four seconds of capture and 100 MB of USB traffic, and you almost certainly wanted a few milliseconds.

Stacked decoders

This is the thing PulseView does that is worth learning. Decoders are not a flat list of protocols — they read each other, and you stack them.

Press the decoder button, add I²C, tell it which channel is SDA and which is SCL. A row appears under the traces with start conditions, addresses, acknowledgements and bytes on it. Then stack a decoder on that row — an I²C device decoder — and it turns the bytes into register names.

The useful thing to take from that structure is where a wrong answer comes from. Only the top row came off the wire; everything under it is software reading the row above using settings you supplied. So a bottom row saying something impossible is nearly always a setting one row up, and the channel assignment is the setting to check first.