Protocol decoders

Protocol decoders

The application runs the unmodified pd.py decoders of libsigrokdecode natively in Python — over 130 of them ship with it, from I²C, SPI and UART to CAN, USB and the mos6502 and c64bus decoders for retro computers.

Adding a decoder

1. Add decoder… in the panel on the right, pick a protocol.
2. Assign the channels. Inputs whose name matches a channel name of the capture are assigned automatically — another reason to name channels before capturing.
3. Set the options (bit rate, word size, address format …).

Decode automatically re-runs the decoders after every capture; Decode now does it on demand. Decoders that consume the output of another one (e.g. a display decoder on top of SPI) can be stacked with the stack button.

Reading annotations

Each decoder produces one or more annotation rows above the waveform.

• Hover an annotation to see how its value is composed: the samples it covers are marked in every view, a dashed line shows where the decoder read the value, and every channel it read shows its level (A15 = 1 (+$8000)). Buses such as A0…A15 also show their value.
• Click the name of a row to open it as a list in a separate window — sample, time, duration, type and value, with a filter and Copy / Copy values. This is the fastest way to read long rows such as a disassembly.

• Double-click an annotation to open that list with the entry selected. Selecting an entry jumps the waveform to it.

Where decoders are searched

In this order — the first decoder with a given id wins:

1. paths given with --decoders (repeatable)
2. the environment variable PIPILOGICANALYZER_DECODERS
3. ./decoders in the working directory
4. decoders in the project directory
5. decoders inside the installed package (the ready-to-run builds)
6. <settings directory>/decoders
7. system paths of libsigrokdecode (/usr/share/libsigrokdecode/decoders, PulseView on Windows, Homebrew on macOS)

Help → Decoder search paths shows the directories and how many decoders were loaded. To add your own, drop it into <settings directory>/decoders/<id>/.

Decoders are Python files that are executed. Treat a decoder from an untrusted source like any other software you install.