Configuration¶

DtolConfig holds process-wide defaults — the fallbacks used when a call site or TaskSpec doesn't specify a value. Anything that varies per task (channel ranges, trigger source, buffer plan) belongs on the TaskSpec, not here.

It is a frozen, slotted, keyword-only dataclass with no validation-library dependency, so importing it costs nothing. Design reference: design.md §19.1.

Fields¶

Field	Default	Meaning
`default_timeout_s`	`10.0`	Fallback SDK read/write timeout (seconds).
`default_sample_rate_hz`	`1000.0`	Fallback `Timing.rate_hz` when unset.
`default_chunk_size`	`1000`	Samples/channel per emitted `DaqBlock` for `record()`.
`default_buffers`	`4`	`BufferPlan.buffers` default (HBUF ring; hard minimum 3).
`default_stream_buffer`	`16`	AnyIO send-stream capacity for `record()`, in `DaqBlock` slots.
`eager_tasks`	`False`	Opt in to `asyncio.eager_task_factory` (no-op on trio).
`oldaapi_dll_path`	`None`	Explicit `oldaapi*.dll` path; `None` uses the loader's resolution chain.
`olmem_dll_path`	`None`	Explicit `olmem*.dll` path.

from dtollib import DtolConfig

cfg = DtolConfig(default_sample_rate_hz=50_000.0, default_buffers=8)
faster = cfg.replace(default_buffers=16)   # immutable copy with one change

From the environment¶

config_from_env(prefix="DTOLLIB_") builds a DtolConfig from environment variables. It is best-effort and never raises — missing or unparseable values fall back to the dataclass default.

Env var	Type
`DTOLLIB_DEFAULT_TIMEOUT_S`	float
`DTOLLIB_DEFAULT_SAMPLE_RATE_HZ`	float
`DTOLLIB_DEFAULT_CHUNK_SIZE`	int
`DTOLLIB_DEFAULT_BUFFERS`	int (clamped at 3 by `BufferPlan`)
`DTOLLIB_DEFAULT_STREAM_BUFFER`	int
`DTOLLIB_EAGER_TASKS`	bool (`1`/`true`/`yes`/`on`)
`DTOLLIB_OLDAAPI_DLL`	path
`DTOLLIB_OLMEM_DLL`	path

from dtollib import config_from_env

cfg = config_from_env()   # reads DTOLLIB_* from os.environ

DLL-path overrides¶

oldaapi_dll_path / olmem_dll_path (and their DTOLLIB_OLDAAPI_DLL / DTOLLIB_OLMEM_DLL env equivalents) feed the loader's resolution chain — useful when the DataAcq SDK is installed in a non-default location. See Installation for the full chain and Troubleshooting for diagnosing load failures.