weather-station-telemetry

Technical Specifications

System Overview

The Weather Station Telemetry System represents a professional-grade embedded solution designed according to aerospace industry standards. This specification document defines the complete technical characteristics, performance parameters, and operational requirements that govern system behavior under various conditions.

Hardware Specifications

Primary Controller Unit

Arduino Uno R3 Microcontroller Platform: The system utilizes the Arduino Uno R3 as its primary processing unit, providing sufficient computational resources while maintaining compatibility with standard development tools and libraries. This choice balances processing capability with cost-effectiveness and educational accessibility.

Processor Specifications:

ATmega328P microcontroller operating at 16 MHz clock frequency
32 KB Flash memory for program storage (2 KB reserved for bootloader)
2 KB SRAM for runtime variable storage and program execution
1 KB EEPROM for persistent data storage (future enhancement capability)
14 digital input/output pins with PWM capability on 6 pins
6 analog input channels with 10-bit resolution

Power Requirements:

Operating voltage range of 7-12V DC via external power jack
USB power capability providing 5V DC at up to 500mA current
Power consumption typically under 50mA during normal operation
Sleep mode capability for battery-powered applications (future enhancement)

Sensor Subsystem

DHT22 Digital Temperature and Humidity Sensor: The DHT22 sensor provides calibrated digital output for both temperature and humidity measurements, eliminating the need for analog signal conditioning and providing enhanced accuracy compared to analog alternatives.

Temperature Measurement Specifications:

Measurement range from -40°C to +80°C covering typical terrestrial conditions
Accuracy specification of ±0.5°C across the entire operating range
Resolution of 0.1°C providing precise measurement capability
Response time of approximately 2 seconds for thermal equilibration
Long-term stability better than ±0.2°C per year under normal conditions

Humidity Measurement Specifications:

Measurement range from 0% to 100% relative humidity
Accuracy specification of ±2% RH across 0-100% range
Resolution of 0.1% RH enabling detection of small humidity changes
Response time of approximately 8 seconds for humidity equilibration
Hysteresis specification of ±1% RH ensuring measurement repeatability

Sensor Interface Characteristics:

Single-wire digital communication protocol reducing wiring complexity
3.3V to 5V power supply compatibility ensuring Arduino compatibility
Built-in signal conditioning eliminates external component requirements
Calibrated factory output eliminates user calibration procedures

Software Architecture Specifications

Real-Time Operating Characteristics

Timing Performance Requirements: The system implements deterministic timing behavior essential for reliable telemetry operation. Measurement cycles execute with precise timing control to ensure data consistency and enable accurate trend analysis over extended periods.

Measurement Cycle Timing:

Primary measurement interval of 30 seconds ±0.5 seconds accuracy
Sensor reading completion within 250 milliseconds maximum
Data validation and formatting completed within 20 milliseconds
Message transmission accomplished within 100 milliseconds at 9600 baud
Complete cycle time under 400 milliseconds leaving ample time for system overhead

Health Monitoring Timing:

Communication health checks performed every 15 seconds during idle periods
Ping-pong protocol timeout specification of 15 seconds maximum wait
Health check completion within 200 milliseconds under normal conditions
Automatic retry with exponential backoff upon communication failure

Memory Utilization Specifications

Program Memory Allocation:

Compiled code size approximately 8.5 KB including all modules and libraries
Remaining flash memory of 23.5 KB available for future enhancements
Bootloader reservation of 2 KB maintained for Arduino compatibility
Library overhead approximately 3 KB for DHT sensor interface

Runtime Memory Management:

Global variable allocation approximately 150 bytes for system state
Stack usage under 300 bytes during peak function call depth
Temporary buffer allocation of 200 bytes for JSON message formatting
Total SRAM utilization under 650 bytes leaving 1.4 KB for expansion

Data Format Specifications

JSON Message Structure: The system implements structured JSON messaging that balances human readability with machine parsing efficiency. This format choice supports both development phases requiring manual inspection and operational phases using automated processing.

Message Field Definitions:

Timestamp field contains milliseconds since system startup enabling duration analysis
Sequential ID field enables message loss detection and ordering verification
Sensor type field supports multiple sensor integration and identification
Value field contains calibrated measurement data in standard engineering units
Success field provides validation status for data quality assessment

Example Message Format:

{
  "timestamp": 1234567,
  "id": 42,
  "type": "sensor_data",
  "sensor_type": "temperature", 
  "value": 23.5,
  "success": true
}

Communication Protocol Specifications

Serial Communication Parameters

Physical Layer Characteristics:

RS-232 compatible UART communication at 9600 bits per second
8 data bits, no parity, 1 stop bit configuration (8N1)
Hardware flow control disabled for simplified three-wire connection
Maximum cable length of 15 meters for reliable communication

Protocol Layer Implementation:

ASCII text transmission ensuring cross-platform compatibility
JSON message framing with newline delimiters for message separation
Bidirectional communication capability supporting command reception
Error detection through message timeout and format validation

Health Monitoring Protocol

Ping-Pong Verification System: The system implements a heartbeat protocol that verifies bidirectional communication capability, ensuring that the ground station can both receive telemetry data and transmit commands to the remote station.

Health Check Sequence:

System transmits “ping” message during idle periods
Ground station responds with “pong” message within timeout period
Successful exchange confirms bidirectional communication capability
Failed exchange triggers communication system reinitialization

Error Recovery Specifications:

Automatic retry with progressive delay increases from 1 to 30 seconds
Maximum retry attempts limited to 5 to prevent infinite loops
Graceful degradation to data transmission only upon persistent failures
System status reporting through enhanced error messages

Performance Specifications

Measurement Accuracy and Precision

Temperature Measurement Performance:

System accuracy combining sensor and processing errors: ±0.6°C maximum
Measurement precision enabling detection of 0.1°C changes
Thermal response time under 30 seconds for step changes
Long-term drift specification under ±0.3°C per year

Humidity Measurement Performance:

System accuracy combining sensor and processing errors: ±2.5% RH maximum
Measurement precision enabling detection of 0.1% RH changes
Humidity response time under 60 seconds for step changes
Long-term drift specification under ±0.5% RH per year

System Reliability Specifications

Operational Reliability Metrics:

Mean time between failures (MTBF) exceeding 8760 hours (1 year)
System availability specification of 99.5% including maintenance periods
Graceful degradation capability maintaining partial operation during component failures
Automatic error recovery without manual intervention requirements

Environmental Operating Conditions:

Operating temperature range from -10°C to +50°C for Arduino electronics
Storage temperature range from -20°C to +70°C for extended preservation
Relative humidity tolerance from 5% to 95% non-condensing
Altitude operation capability up to 2000 meters above sea level

Interface Specifications

User Interface Requirements

Development and Debugging Interface:

Serial monitor access through USB connection at 9600 baud rate
Real-time telemetry display with timestamp and measurement identification
Error message reporting with specific failure mode identification
System status indicators showing operational state and component health

Operational Interface:

LED indicator showing power and activity status
JSON telemetry output compatible with standard parsing libraries
Structured error reporting enabling automated fault diagnosis
Configuration parameter access through code modification

Expansion Interface Specifications

Additional Sensor Integration:

Digital I/O pins available for additional sensor connections
Analog input channels supporting traditional sensor interfaces
I2C and SPI communication protocols available for advanced sensors
Power supply capability supporting moderate sensor current requirements

Communication Enhancement Options:

Ethernet shield compatibility for network-based telemetry
WiFi module integration capability for wireless communication
SD card interface support for local data logging
GPS module integration for position reporting

Compliance and Standards

Software Development Standards

Code Quality Requirements:

Modular architecture following NASA software development guidelines
Comprehensive error handling at all system levels
Defensive programming practices preventing undefined behavior
Documentation standards ensuring maintainability and knowledge transfer

Testing and Validation Standards:

Component-level testing for individual module verification
Integration testing for module interaction validation
System-level testing under operational conditions
Performance verification against specification requirements

Safety and Regulatory Considerations

Electrical Safety Compliance:

Low voltage operation under 12V DC eliminating shock hazards
Overcurrent protection through USB port current limiting
Proper grounding practices preventing static discharge damage
Component selection based on automotive/industrial temperature ratings

Electromagnetic Compatibility:

Digital communication protocols minimize electromagnetic interference
Shielded cable recommendations for electrically noisy environments
Grounding specifications for professional installation practices
Frequency selection avoiding interference with critical communication bands

These technical specifications provide the complete engineering foundation for implementing, testing, and maintaining the Weather Station Telemetry System according to professional embedded systems standards.

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