qspice-mixed-signal-dll

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. Preferred: one-call device spec. For multi-pin devices (controllers, microcontrollers), call describe_device_spec for the PinDef-style JSON schema, then create_dll_device_from_spec — it places the block with every pin (inline device_name + pins, or a workspace spec file) and can scaffold the contract-matched C++ source in the same call. Skip to step 5.
3. Manual path: 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).
4. 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 and a per-instance state struct (opaque allocation idiom). Edit the generated .cpp with write_workspace_text_file.
5. 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.
6. Validate. validate_dll_symbol_signature cross-checks the symbol's pins against the source so the block and code can't silently drift.
7. Simulate. generate_netlist then run_simulation — DLL blocks are emitted correctly (not as unresolved subcircuits) by the clean-room netlister.