Design Ideas

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This page contains random design ideas, and should be fleshed out into something a bit closer to later design decisions that were made.

Contents

General principles

  • Use the GNU GPL to ensure all modifications are contributed back to the project etc.
  • Use C for speed, optimize data set handling/summarization.
  • Backend:
    • The backend should be completely separate from any frontends, and will do this:
      • Interface with hardware modules via a device plugin system.
      • Data summarization on in-memory buffer and live stream to produce a canvas-sized dataset.
      • Interface with protocol analysis modules via a PA plugin system.
      • Interface with a frontend via a generic API, which every frontend must provide.
  • Command line:
    • Should support at least grabbing data from an LA and dump to a file, with cmdline parameters/triggers.
  • GUI:
    • Cross-platform UI via Qt 4 (including support for Linux, Mac OS X, Windows and many other OSes).
    • Some shared semi-GUI components, e.g. code for rendering datasets and protocol analysis results onto a canvas, with platform-specific callbacks to draw actual dots/lines/boxes/text(?)
    • A GUI implementation must never have a feature that isn't supported by all other GUI implementations.
    • Support for multiple languages / translations of the UI (made easy by Qt).

Hardware support

  • Target hardware: See Supported hardware.
  • Probe for supported USB hardware on the bus when starting up: vendor/product IDs are easy to find.
    • Use libusb 1.0 for platform-independent USB handling code.
  • Should support hotplugged USB devices automagically — is there a platform-independent way to do this?

Protocol decoders

See Protocol decoders.

Data Analysis (DA)

A plugin system that feeds the stream to a DA, and gets either a report or a set of key/value pairs to display. A DA plugin does not necessarily return data that can be displayed alongside the original data stream (though it can do that, too); it usually provides an analysis that works on the whole stream. It should still be fed samples in real time though, and have the possibility of providing live analysis, e.g. for output into a graphing component.

In order to be able to report or graph relevant data, the DA plugin should hint at the type of data it returns. For example it might output clock deviation as a type meaning "an array of numbers between -1 and +1".

Example ideas for DA plugins:

  • Analysis of a PWM signal: report duty cycle, deviation from duty cycle, pipe deviation over time into graphing component (PWM catpure).
  • Count, analyze, and determine various datapoints, e.g:
    • Input = SPI data. Output = how many pixels were set on the SPI-attached display.
    • Input = Raw signals of (for example) 5 channels. Output: Which of the lines is (likely) TDO, which one is TDI, etc?
    • Input = Raw signals of some channels. Possible outputs:
      • Which protocol is this likely to be (SPI? UART? JTAG? I2C? etc.)
      • Which parameters apply to that protocol?
        • SPI: Rising or falling clock edge?
        • SPI: At which MHz rate does the communication take place?
        • UART: Which Baud rate was used?
        • UART: How many stop bits? Parity?
        • How many (and which) I2C slaves communicated here?
        • LPC/FWH: Which BIOS chip was the host/master talking to (chip vendor ID and device ID)?
    • ...

Example output:

Flags Key Value
INTEGER | PERCENTAGE Duty Cycle 50
INTEGER | ARRAY | DEVIATION Duty Cycle deviation [-0.01, 0.02, ...]

Platform-independent GUI features

  • Initial interface should be friendly and not complex.
  • Lightweight canvas for main analysis display, summarize data according to zoom level.
  • Change zoom level with mouse wheel, scrollbar (min=~10 samples on screen, max=all of it for memory display, or 1 second's worth for live stream).
  • Keep options open for supporting full oscilloscope streams, not just logic streams. While a full scope needs more options, having a resolution parameter per dataset would already help: 1 bit for LA, e.g. 8 or 16 bits for scope.
  • Since some protocol analyzers could operate on top of another PA, this implies a "layer" system. The GUI must provide a way to view/hide specific layers.
  • Mode to display the received/sent protocol analysis layers in a hexdump/clean ASCII display, not just the level graph.

Miscellaneous features

  • Save session:
    • Configured analyzers, triggers, pin names, UI colors.
    • Hardware used + metadata (port, ...), capture timestamp.
    • Captured data.
    • Need to work out a file format (versioned, extensible!).
  • Export any data layer (captured data, different levels of PA) to raw, CSV, VCD, ODS, and many other formats.
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