qspice-mixed-signal-dll

name	qspice-mixed-signal-dll
description	Author, scaffold, build, and validate QSpice `.DLL` custom-device blocks for mixed-signal C/C++ models. Use when adding a controller or behavioral block backed by compiled code, generating a C++ scaffold from a symbol, building the DLL, or checking that a symbol matches its source.
license	MIT
metadata	{"author":"qspice-mcp","version":"1.0"}

QSpice: Mixed-Signal .DLL Custom Devices

QSpice runs compiled C/C++ models as .DLL custom-device blocks. This skill covers the full loop: place the block, generate matching source, build it, and prove the symbol and source agree.

When to use

• A circuit needs a digital controller, state machine, or behavioral block that is easier to express in code than in SPICE primitives.
• You have a .DLL symbol and need a C++ scaffold, or a source file and need to verify it matches the symbol.

When NOT to use

• Pure analog authoring/placement → qspice-getting-started and qspice-schematic-layout.
• A simulation that runs but won't converge → qspice-convergence-debugging.

Workflow

1. Check support. describe_mixed_signal_support to confirm which scaffold generators and build toolchains (bundled DMC, MSVC cl, CMake) are available on this machine.
2. Place / shape the block. add_dll_block to insert a block with starter input/output pins; adjust the interface with add_dll_block_pin, remove_dll_block_pin, and set_dll_block_pin_role (input vs output preset).
3. Generate source. scaffold_dll_device_from_symbol emits a C++ stub plus a CMakeLists.txt next to the schematic, with the pin signature already wired. Edit the generated .cpp with write_workspace_text_file.
4. Build. build_dll_device compiles the source to a .dll (prefers bundled DMC, falls back to MSVC/CMake). See the C-Block Build Guide for prerequisites.
5. Validate. validate_dll_symbol_signature cross-checks the symbol's pins against the source so the block and code can't silently drift.
6. Simulate. generate_netlist then run_simulation — DLL blocks are emitted correctly (not as unresolved subcircuits) by the clean-room netlister.

Notes

• generate_dll_variables produces .DLL variable declarations via the QUX companion path when you need them.
• The symbol is the contract: pin order/names in the symbol must match the source's port list. Re-run validate_dll_symbol_signature after editing either.
• If no toolchain is present, build_dll_device reports a degradation rather than guessing — install MSVC build tools or rely on bundled DMC.

Conventions

• Keep the .cpp, CMakeLists.txt, and .qsch in the same workspace folder so QSpice's Show Source and the build commands resolve relative paths.
• Validate before simulating; a mismatched signature fails confusingly at sim time.