• Monitor core indoor environmental conditions with stable and repeatable measurements.
• Support integration with a smart home ecosystem through a suitable communications interface.
• Minimize power consumption during both active sensing and idle operation.
• Fit within a compact PCB outline suitable for enclosure-based deployment.
• Support reliable prototype bring-up, test, and debug.
• Allow future expansion for additional sensors or interface options.
• Use practical, manufacturable design choices appropriate for small-run production.

• Include sensing for temperature and humidity.
• Include at least one additional sensor input such as ambient light, motion, or air quality.
• Include a main processing device capable of reading sensors and managing communications.
• Include a regulated onboard power subsystem for all required voltage rails.
• Include programming and debug access for firmware development and bring-up.
• Include a communications path for smart home integration.
• Include basic status indication for power and board activity.
• Include connector or mounting provisions appropriate for enclosure installation.
• Include appropriate decoupling, filtering, and protection to support stable operation.

Json
{
  "device_type": "smart_home_sensor_board",
  "sensors": ["temperature", "humidity", "ambient_light", "motion"],
  "sample_interval_seconds": 60,
  "report_interval_seconds": 300,
  "low_power_mode": true,
  "diagnostics": {
    "heartbeat": true,
    "fault_reporting": true
  }
}

• The board is intended for typical indoor smart home environments.
• The PCB should remain compact and suitable for enclosure integration.
• Low power consumption is a primary design constraint.
• Parts selection should consider availability, lifecycle, and sourcing risk.
• The design should avoid unnecessary cost and excessive complexity.
• The board should be practical to manufacture and assemble with standard PCB processes.
• The design should support straightforward debug and validation during bring-up.