KaraZajac
45 lines
1.3 KiB
Markdown
45 lines
1.3 KiB
Markdown
---
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layout: default
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---
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# Scher-Khan Protocol
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**Rust module:** `src/protocols/scher_khan.rs`
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**Reference:** `REFERENCES/ProtoPirate/protocols/scher_khan.c`
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## Overview
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Scher-Khan is decode-only. PWM: 750 µs = 0, 1100 µs = 1; preamble uses 2× short then alternating. Variable bit count (35, 51, 57, 63, 64, 81, 82); only 51-bit format is parsed for serial/button/counter. Reference: phreakerclub.com/72.
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## Timing
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| Parameter | Value | Notes |
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|-----------|---------|---------|
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| Short (0) | 750 µs | ±160 µs |
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| Long (1) | 1100 µs| ±160 µs |
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| Min bits | 35 | (variable) |
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## Encoding
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PWM; preamble: two short then alternating short/long.
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## Frame Layout (variable)
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- **51-bit format:** serial (28) | button (4) | counter (16) — “MAGIC CODE” / Dynamic; parsed for serial/btn/cnt.
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- Other lengths (35, 57, 63, 64, 81, 82) decoded as raw bit count but not field-parsed.
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## Decoder Steps
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1. **Reset** — Wait for preamble (2 short + alternating).
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2. **CheckPreamble** — Confirm preamble pattern.
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3. **SaveDuration** — Store pulse duration.
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4. **CheckDuration** — Short–short = 0, long–long = 1 (or equivalent); add bit; on end marker, if bit_count in {35,51,57,63,64,81,82} return decode (51-bit parsed for fields).
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## Encoder
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Not implemented (no encoder in reference).
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## Frequencies
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433.92 MHz.
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