Common to All Modules

Devices, experiments and analyzers are different kinds of module (see The three things you build), but they share the same ground: how they are configured, how they log what they do, and the data types they exchange. This chapter covers that shared ground once, so the chapters on each kind of module do not repeat it.

Where each kind of setting goes

A module is configured in three places. Choose the place by asking who the setting belongs to:

The setting belongs to …	Example	Goes in	Explained in
this computer or this lab, or is secret	an instrument’s address, a server’s port, a password	.env	The .env File
the module itself	motor counts per degree, a hardware speed limit, which devices an experiment uses	config.yaml inside the package	The module configuration: config.yaml
one measurement	the wavelengths to scan, the exposure time	config/*.yaml (experiments only)	The run configuration: config/*.yaml

Getting this right is what lets the same module run in another lab unchanged: only .env differs.

In this chapter

Page	Covers
The .env File	settings that differ per computer, and the variables plesty-lib reads by itself
YAML Configuration	the module’s own config.yaml, and an experiment’s run settings
Logging System	where a module’s log messages go, and how to control them
Data & Metadata Schemas	the data types devices produce, experiments record and analyzers read