logisim271-mcp

MCP server that builds and verifies circuits as Logisim 2.7.1 .circ files (classic Carl Burch Logisim, not Evolution). Simulation runs the real 2.7.1 via java -jar logisim-win-2.7.1.exe file.circ -tty table.

Tools

High-level builders auto-place and auto-wire, then verify the full truth table in Logisim.

Related MCP server: Logisim-evolution MCP Server

2.7.1 facts this relies on (all measured, see tests/)

• Gate loc = output point. Size 50 input offsets (east): 2 → ±20; 3 → -20,0,20; 4 → -20,-10,10,20; 5 → -20..20 step 10. Input x = loc − 50 (AND/OR), −60 (NAND/NOR, XOR), −70 (XNOR), −30 (NOT), −20 (Buffer).

• Default inputs is 5; XOR default is "exactly one" → we write xor="odd" (parity).

• -tty table settles once with input pins at 0 (pin values aren't saved), prints output pins sorted by (y, x), tab-separated, multi-bit as binary, x floating / E error, then never exits. We read one line and kill the JVM. To evaluate many rows in one run, the circuit is copied once per row with input pins replaced by Constants.

• A wire end touching another wire mid-span connects; mid-span crossings don't.

• tty mode does tick Clock components and prints a line each time an output changes. simulate_sequential replaces the clock pin with a Clock and adds a second Clock wired to a top-most output pin, so every half period yields one line (line 0 = power-on, line 2k-1 = after rising edge k). Non-clock inputs are held constant for the whole run (no per-cycle input sequences yet).

Install (Claude Code)

Requirements: Java 8+, Python 3.10+, uv, and Logisim 2.7.1 (logisim-win-2.7.1.exe or logisim-generic-2.7.1.jar from SourceForge). Logisim is not bundled.

claude mcp add logisim271 --env LOGISIM_JAR=C:/path/to/logisim-win-2.7.1.exe -- uvx --from git+https://github.com/JunghyunLee1122/logisim271-mcp logisim271-mcp

Then ask e.g. "full adder 만들어줘" / "build a 4-bit ripple adder in adder.circ and verify it".

Development

py -3.13 -m venv .venv
.venv/Scripts/python.exe -m pip install -e ".[dev]"
LOGISIM_JAR=../logisim-win-2.7.1.exe .venv/Scripts/python.exe -m pytest

Env: LOGISIM_JAR (2.7.1 exe or jar), JAVA (java executable), LOGISIM_WORKDIR (base for relative paths).