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name: similarity-mcu description: Use when working with MCU/microcontroller similarity calculations - comparing microcontroller MPNs, understanding family/series/feature matching, or MCU-specific similarity logic.

MCU Similarity Calculator Skill

Guidance for working with MCU similarity calculators in the lib-electronic-components library.

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For metadata-driven similarity architecture, see /similarity-metadata:

• SpecImportance levels (CRITICAL, HIGH, MEDIUM, LOW, OPTIONAL)
• ToleranceRule types (exactMatch, percentageTolerance, minimumRequired, etc.)
• SimilarityProfile contexts (DESIGN_PHASE, REPLACEMENT, COST_OPTIMIZATION, etc.)
• Calculator integration patterns and gotchas

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Overview

There are two MCU-related calculators:

MCUSimilarityCalculator (Simple Interface)

• Implements SimilarityCalculator
• Uses pattern matching for family/series/features
• No PatternRegistry required

MicrocontrollerSimilarityCalculator (Component Interface)

• Implements ComponentSimilarityCalculator
• Uses manufacturer handlers for extraction
• Requires PatternRegistry

Applicable Types (MicrocontrollerSimilarityCalculator)

CopyComponentType.MICROCONTROLLER
ComponentType.MICROCONTROLLER_ATMEL
ComponentType.MICROCONTROLLER_INFINEON
ComponentType.MICROCONTROLLER_ST
ComponentType.MCU_ATMEL

Similarity Weights (MCUSimilarityCalculator)

CopyfamilySimilarity * 0.5   // Family is most important
seriesSimilarity * 0.3   // Series number
featureSimilarity * 0.2  // Feature codes (F, L, U, etc.)

MCU Families

Family Groups

Copy// Same family = 1.0 family similarity
calculator.calculateSimilarity("STM32F103", "STM32F407");
// High similarity (same STM32 family)

// Related family = 0.8 family similarity
calculator.calculateSimilarity("PIC16F877", "PIC18F4550");
// Good similarity (both PIC family)

Feature Codes

Copy// Same feature codes contribute to similarity
calculator.calculateSimilarity("STM32F103", "STM32F407");
// Both have F (Flash) feature

Series Similarity

Series numbers are compared numerically:

• Same series = 1.0
• Close numbers (within 100) = partial similarity
• Far numbers = lower similarity

Copy// Same series
calculator.calculateSimilarity("ATMEGA328", "ATMEGA328P");
// Very high similarity

// Close series
calculator.calculateSimilarity("ATMEGA328", "ATMEGA329");
// High similarity

// Far series
calculator.calculateSimilarity("ATMEGA328", "ATMEGA2560");
// Lower similarity

MicrocontrollerSimilarityCalculator Scoring

Test Examples

MCUSimilarityCalculator

Copy// Identical MCU
calculator.calculateSimilarity("ATMEGA328P", "ATMEGA328P");
// Returns 1.0

// Same family, different series
calculator.calculateSimilarity("STM32F103", "STM32F407");
// Returns > 0.5

// Different families
calculator.calculateSimilarity("STM32F103", "ATMEGA328");
// Returns lower similarity

MicrocontrollerSimilarityCalculator

Copy// Same part, different package
calculator.calculateSimilarity("ATMEGA328P-AU", "ATMEGA328P-PU", registry);
// Returns >= 0.5

// Different MCUs
calculator.calculateSimilarity("ATMEGA328P", "STM32F103C8T6", registry);
// Returns 0.5 (base MCU similarity)

Common MCU Patterns

Atmel/Microchip AVR

CopyATMEGA 328 P -AU
│      │   │  │
│      │   │  └── Package (AU=TQFP)
│      │   └───── Variant (P=Picopower)
│      └───────── Series number
└──────────────── Family

STMicroelectronics STM32

CopySTM32 F 103 C8 T6
│     │ │   │  │
│     │ │   │  └── Package (T6=LQFP48)
│     │ │   └───── Memory/pins
│     │ └───────── Series
│     └─────────── Type (F=Foundation)
└───────────────── Family

Microchip PIC

CopyPIC16 F 877 A
│     │ │   │
│     │ │   └── Variant
│     │ └────── Series
│     └──────── Memory type (F=Flash)
└────────────── Family

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Learnings & Quirks

Family Detection

• Regex ^([A-Z]+)\d+ extracts family prefix
• Empty family = 0.0 family similarity

Series Number Extraction

• Extracts first numeric sequence
• Compared as integers for proximity

Feature Code Position

• Usually at end of part number
• Regex [A-Z]+$ extracts trailing letters

Package Codes

• Vary significantly by manufacturer
• Don't affect core part equivalence
• Same MCU in different package = HIGH similarity

Cross-Family Comparison

• Different families get Levenshtein similarity
• Never returns > 0.8 for different families