essim/doc/user/index.md

essim — user guide

A short, task-oriented introduction to using essim. For step-by-step batch and TUI walkthroughs, see tutorial.md. For an exhaustive reference of every command, see commands.md (auto-generated from the binary). For scripting and $variable expansion, see scripting.md.

What essim is

A digital twin for the inter-card connections inside a system. You load modules (cards/boards) from netlist or pinout files, tag their connectors with a connector_type, connect them across modules, and verify that the signal types match the connector role expectations. You can save a snapshot, restore it later, or replay a session as a script.

┌──────────┐    ┌──────────┐
│ Module A │    │ Module B │
│  Part J1 │←──→│  Part P1 │   <— a Connection (built by `connect`)
│   pins   │    │   pins   │
└──────────┘    └──────────┘

First session

After launching ./build/essim, the prompt accepts a sequence of commands. The most common bring-up looks like this:

> new
> load backplane /path/to/netlists/backplane.NET altium
> load payload1  /path/to/netlists/payload.qcv mentor
> set-connector-type backplane J20 vpx-3u-bkp-p0
> set-connector-type payload1  P0  vpx-3u-payload-p0
> connect backplane J20 payload1 P0
> verify
> save my-system.essim

Things to try at any time:

Action	How
List every command	help
Help on one command	help <name>
Scroll back through output	PageUp / PageDown, Home, End
Re-run a previous command	↑ / ↓ (also history is on disk)
Tab-complete a command name	set‹Tab› → set-connector-type etc.
Cancel a multi-step prompt	Esc
Leave essim	quit (or exit)

Interactive screens

Some commands open a dedicated full-screen layout when invoked with no arguments (the help listing tags these [interactive]). They all share the same conventions:

• A title bar essim → <name> — <short description> is shown at the top.
• Tab cycles focus between fields; the active field's label flips to reverse video so it's obvious where the next keystroke goes.
• Esc leaves the screen and returns to the main prompt.
• The screens are user-facing only — they are never allowed inside a sourced script. A sourced script must use the inline form of these commands instead.

Today's interactive screens: connect, set-connector-type, explore, analyze. See commands.md for each.

Saving, restoring, replaying

Three orthogonal mechanisms persist your work:

• save <file> writes a binary-tab-delimited snapshot of the whole system (modules, parts, signals, connector types, signal-type overrides, connections, pin maps). restore <file> replaces the current system with the snapshot.
• script-save <file> writes a replay-ready text script of every command issued since the last new. The interactive bits and the noisy commands (clear, help, …) are filtered out automatically.
• source <file> reads a script line by line. Comments start with #, blank lines are skipped, leading ~/ in paths is expanded, and while a script is running a centred "Computing…" modal shows the progress (one line per ~30 ms tick).

A typical workflow: experiment in the shell, script-save the part that works, hand-edit the script to introduce $variables (see scripting.md), then source it whenever you start fresh.

Where to look next

• tutorial.md — end-to-end batch and TUI walkthroughs, including BSDL attach + the pin/JTAG checks.
• commands.md — exhaustive command reference, regenerated from the binary on every cmake --build build --target doc.
• analysis.md — how essim classifies signals (Power / Gnd / Other), how it detects buses and diff pairs, what the analyze screen actually reports and why.
• scripting.md — set / $var / ${var}, source semantics, the script-save denylist.
• DESIGN.md — implementation notes, useful if you want to add a command or a screen.
• ../api/ — auto-generated C++ API reference.