WiFi and Bluetooth Sensor Node Design
Make me a temperature and humidity sensor node with Wifi and Bluetooth, powered by USB-C (5V) for consumer use.
It should be a low-power environmental node with a digital T/RH sensor, ultra-low-power MCU with Wi-Fi + Bluetooth (dual-radio) — 2.4 GHz 802.11 b/g/n plus BLE 5.x powered by USB-C (5 V) — USB-C receptacle 5 V default; include reverse/OVP/UVLO/OCP protection and plan for 0.5–3 A sources.
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High-Level Execution Plan
Project Goal
Create a consumer USB-C powered, low-power temperature and humidity sensor node that:
- Accepts 5 V from USB-C default current sources
- Measures ambient temperature and relative humidity with a digital sensor
- Uses an ultra-low-power MCU with dual-radio 2.4 GHz Wi-Fi (802.11 b/g/n) and Bluetooth Low Energy 5.x
- Includes front-end power protection for reverse polarity, over-voltage protection (OVP), under-voltage lockout (UVLO), and over-current protection (OCP)
- Is suitable for a consumer product workflow, from requirements definition through prototype validation
1. Requirements Capture
Define and freeze the top-level product requirements before schematic work begins.
Capture
- Product purpose and operating concept
- Power source assumptions: USB-C sink, 5 V only, no USB-PD negotiation
- Functional scope: sensing, local processing, wireless connectivity, status/reporting behavior
- Low-power goals: operating modes, sleep behavior, wake intervals, battery-less behavior on cable removal if applicable
- Environmental requirements: operating temperature/humidity range, enclosure assumptions, sensor placement constraints
- Wireless expectations: provisioning method, Wi-Fi/BLE usage model, antenna/enclosure constraints, regional compliance targets
- User-facing requirements: indicators, buttons, reset/recovery expectations, debug/service access
- Reliability and protection requirements: reverse polarity, OVP, UVLO, OCP, ESD/consumer handling expectations
- Manufacturing targets: target cost band, prototype quantity, assembly strategy, test expectations
Output
- Approved project specification with measurable requirements and out-of-scope items
2. System Architecture Definition
Translate the requirements into a block-level system architecture.
Define major blocks
- USB-C power entry and protection block
- Power regulation and always-on / switched power domains
- MCU + radio subsystem
- Digital temperature / humidity sensing subsystem
- Programming, debug, and recovery interface
- User/status interface block
- RF/antenna implementation approach
Decisions to lock at this stage
- Power domain strategy and startup/shutdown behavior
- Wireless architecture assumptions and provisioning flow
- Sensing cadence versus power budget strategy
- Partitioning between always-powered, sleep-capable, and active domains
- Mechanical constraints that affect RF and sensor accuracy
Output
- Block diagram and interface definition between major subsystems
3. Implementation Planning for Core Design Areas
Plan the major design workstreams without doing component-level selection yet.
Power + Protection workstream
- Define USB-C sink-only implementation for 5 V default current sources
- Define required protection chain and fault-handling behavior for reverse polarity, OVP, UVLO, and OCP
- Define normal operating voltage ranges, fault thresholds, startup sequencing, and reset behavior
- Define efficiency and standby-power objectives
Compute + Wireless workstream
- Define MCU responsibilities, memory/peripheral needs, and firmware architecture assumptions
- Define Wi-Fi and BLE roles, coexistence expectations, and antenna placement constraints
- Define required interfaces for sensor, debug, and user controls
Sensor workstream
- Define sensing accuracy, update rate, placement constraints, and contamination/thermal isolation considerations
- Define digital interface assumptions and data quality / filtering expectations
Productization workstream
- Define design-for-test strategy, programming flow, serial numbering / identity needs, and manufacturing checkpoints
- Define compliance considerations: EMC, RF certification path, ESD robustness, consumer USB expectations
Output
- Workstream owners, dependencies, and success criteria
4. Schematic Capture Plan
Create the schematic in clearly separated functional sections.
Major schematic sections
- USB-C connector and input conditioning
- Protection and power regulation
- MCU/radio core
- Sensor interface and local filtering
- Boot, reset, programming, and debug circuitry
- Indicators / user interface
- RF-related support and keepout-aware circuitry
- Test points and production support
Execution approach
- Start with power-entry and protection path
- Add core compute/wireless subsystem
- Add sensor and support interfaces
- Add bring-up, programming, and debug provisions
- Review net naming, rail naming, and design documentation before layout begins
Output
- Reviewed top-level schematic organized by functional blocks
5. Layout Planning
Plan PCB implementation before routing.
Define up front
- Board size class and mechanical constraints
- Layer strategy based on RF, noise, and product density needs
- Placement priorities: USB-C entry, protection path, MCU/radio, antenna region, sensor exposure area
- Grounding and return-path strategy
- Isolation between heat-generating / noisy circuitry and the temperature-humidity sensor
- RF keepout and enclosure interaction assumptions
- Test access and manufacturing clearances
Output
- Placement strategy and layout constraints ready for PCB execution
6. Firmware and Bring-Up Planning
Define the minimum firmware scope needed to validate hardware.
Plan
- Boot and recovery strategy
- Hardware bring-up checklist for rails, clocks, interfaces, and radios
- Sensor readout and basic data validation flow
- Low-power state validation plan
- Wireless provisioning, connectivity test, and telemetry demonstration plan
- Factory-test / board-test firmware mode requirements
Output
- Firmware bring-up plan and validation sequence for first prototypes
7. Verification and Review Plan
Establish major validation gates before prototype release.
Review gates
- Requirements review
- Architecture review
- Schematic review
- Layout review
- Pre-release ERC/DRC and manufacturability review
Validation areas
- Power-up / fault handling behavior
- USB-C input behavior under expected source conditions
- Protection feature behavior under abnormal conditions
- Sensor performance under realistic thermal and humidity conditions
- Wireless functionality and range sanity check
- Low-power performance versus target
- Programming / debug / recovery robustness
Output
- Test plan with pass/fail criteria for prototype acceptance
8. Prototype, EVT, and Iteration Plan
Prepare for first build and learning cycle.
Steps
- Release prototype package for assembly
- Perform structured bring-up and issue logging
- Compare measured behavior against requirements
- Identify changes for next revision: power, RF, sensing, mechanical, manufacturability, firmware
- Update design documents and risk list after first hardware evaluation
Output
- Revision plan for the next prototype spin
Suggested Milestone Sequence
- Requirements frozen
- Block architecture approved
- Power/protection behavior defined
- Schematic complete and reviewed
- Layout constraints approved
- PCB layout complete and reviewed
- Prototype build released
- Bring-up complete
- Validation complete
- Revision decisions recorded
Scope Guardrails
To keep execution efficient, defer these until after requirements and architecture are stable:
- Exact component selection
- Threshold calculations
- RF matching optimization
- Detailed firmware implementation
- Mechanical enclosure optimization beyond stated constraints
- Cost-down optimization before first validation build
Project Goal
1. Requirements Capture
Capture
Output
2. System Architecture Definition
Define major blocks
Decisions to lock at this stage
Output
3. Implementation Planning for Core Design Areas
Power + Protection workstream
Compute + Wireless workstream
Sensor workstream
Productization workstream
Output
4. Schematic Capture Plan
Major schematic sections
Execution approach
Output
5. Layout Planning
Define up front
Output
6. Firmware and Bring-Up Planning
Plan
Output
7. Verification and Review Plan
Review gates
Validation areas
Output
8. Prototype, EVT, and Iteration Plan
Steps
Output
Suggested Milestone Sequence
Scope Guardrails
