U3LogicAnalyzer Tutorial for Using

Supported devices: WeAct Studio Logic Analyzer V1 / V2

#Window layout

The UI follows the system language. To pick one by hand: Help → Settings → "User interface language". The choice applies immediately.

#Connecting a board

The device is scanned as soon as it is plugged in, and the device selector shows model and port, e.g. WeAct Studio Logic Analyzer V2 ch375/5-2.

• One board: it is the only entry, just start capturing.
• Several boards: the list holds one row per port. Each row has "open in a new session" on the right, so every board can capture into a page of its own, at the same time.
• Hot plug: unplugging the board that is capturing leaves that page behind an offline mask - a capture cannot be started there until the board is back. Boards coming and going while a capture runs do not disturb it.

On Windows the CH375DLL driver is the default (back end wch-ch32h417), so it works out of the box with no driver install. To use the libusb back end (wch-ch32h417-libusb) instead - or an FX2 based analyzer - the device has to be rebound to WinUSB first.

#Installing the libusb driver (Zadig) — only needed for an FX2 board or the libusb back end

This is the same procedure as the driver setup in the LogicAnalyzerV1 tutorial. Two things differ for the Logic Analyzer V2: first uninstall the device's CH375 driver in Device Manager — right-click the device and tick "delete the driver software for this device" — then replug it; and in Zadig you do not rename the device to fx2lafw the way an FX2 board needs.

1. Plug the analyzer in and start Zadig. PulseView ships a copy in its install folder; otherwise get it from zadig.akeo.ie.
2. Options → List All Devices, so the list shows everything.
3. Select the analyzer in the drop-down. It is listed as Logic Analyzer V2; check the USB ID to tell it apart from similarly named HID devices such as a keyboard.
4. Set the target driver to WinUSB.
5. Click Install Driver and let the progress bar finish.
6. Unplug and replug the device.

Once rebound, the default CH375DLL back end no longer sees the board. To go back: uninstall the device in Device Manager with "delete the driver software for this device" ticked, replug it, then reinstall the CH375 driver from the driver folder in the application's install directory.

#Device options

The gear button opens Device Options:

Changing the channel count rebuilds the sample rate table. That is a property of the device, not a bug: settle the channel count first, then pick the rate.

#Sample rate and sample count

• Sample rate: 25 steps from 4 MHz to 200 MHz on a USB 3.0 link; the table follows the link and the channel count (4 to 20 MHz at 16 channels, 4 to 40 MHz at 8 channels on USB 2.0).
• Sample count (the duration box): from 10 ms up; the upper bound depends on PC memory (samples = rate × time, 2 bytes per sample at 16 channels; the software works from an 18 GB data ceiling, so 200 MHz / 16 ch is about 45 s and twice that at 8 channels).

Rules of thumb:

#Capturing

Press Start on the tool bar, or the space bar, and press it again to stop. When the capture ends the view zooms to fit the data.

• Mode → Single: stops once the set number of samples is in.
• Mode → Repeat: captures continuously until stopped; each round replaces the previous one.
• Pre-trigger: at 50% half of the window holds the samples before the trigger, the rest after. The device has no hardware trigger unit - the setting divides the capture window, which is what you need to see the state a signal came from.
• Long captures: everything stays in memory. The application watches the free memory while the data comes in and stops the capture below 512 MB with a message, keeping what was captured. Fewer channels, a lower rate or a shorter run is what makes a longer capture fit.

#Reading the waveform

#Protocol decoders

The Decoder button (or D) opens the panel on the right:

1. Type a name into the search box, e.g. uart, i2c, spi.
2. Open a category, or double click the decoder in the search result.
3. In the dialog that follows, map the channels and set the options (RX channel and baud rate for UART, for instance), then confirm.
4. The decoded rows appear under the waveform; Decoding Result switches to a list view of them.

A session can stack several decoders - SPI flash commands and data on one bus, say. There are 132 of them; the full list is in the decoders folder of the install directory (e.g. C:\Program Files\WeAct Studio\U3LogicAnalyzer\decoders).

Decoded results can be exported: the Export button writes several text formats, and "Export to a New Session" copies the waveform and its decoders into a new tab so the original capture stays untouched.

#Saving and exporting

• Save / Save As: a sigrok session file (.sr, a zip container) with the channel data and the sample rate. An 8 channel capture stays 8 channels wide and is not read back as 16.
• Save Selected Range As: only the samples in the current view.
• Save Session Setup: the configuration only (device options, decoders, view), no data.
• Open: from the menu, or on the command line:

./U3LogicAnalyzer capture.sr        # Windows: U3LogicAnalyzer.exe capture.sr
./U3LogicAnalyzer -i capture.sr

A file brings the channels it actually holds: those are the ones given a row, and the channel popup lists them alone.

#Sessions and several devices

• The tab bar at the bottom holds several sessions at once: one per board, or one per .sr file.
• The first session cannot be closed, and opening a file always adds a tab.
• "Export to a New Session" copies the result into a tab of its own; the capture it came from is left as it was.
• Closing the last file tab brings the device session back.

#Firmware update

Help menu → FW Update.

• The update runs over the device IAP. The tab cannot be closed while it runs, so an interrupted write cannot leave the board stuck in its bootloader without a page to retry from.
• Progress is shown over the page; the device reconnects and is read again when it is done.
• Do not unplug during the write. If it fails, retry - the board is still in IAP mode.

#Troubleshooting

The board is not in the device list

• Windows: make sure no other program holds it; the libusb back end needs a WinUSB rebind with Zadig first.
• Linux: lsusb lists it but the application does not - that is a permission problem. Run sudo ./install_udev_rules.sh and replug.

The capture stops at once with 0 samples

• The sample rate is beyond what the link carries, or the sample count is too large. Lower the rate or shorten the duration and try again.
• The board may still be held by a previous program: unplug and replug it.

The UI is in a language I did not pick

• Help → Settings → "User interface language" and pick the one you want.

A low memory notice appears at startup

• The application checks the free memory before it starts and asks for confirmation below 4 GB. Close something, or just confirm.