leviathan
41 lines
1.3 KiB
Markdown
41 lines
1.3 KiB
Markdown
# Scher-Khan Protocol
|
||
|
||
**Rust module:** `src/protocols/scher_khan.rs`
|
||
**Reference:** `REFERENCES/ProtoPirate/protocols/scher_khan.c`
|
||
|
||
## Overview
|
||
|
||
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.
|
||
|
||
## Timing
|
||
|
||
| Parameter | Value | Notes |
|
||
|-----------|---------|---------|
|
||
| Short (0) | 750 µs | ±160 µs |
|
||
| Long (1) | 1100 µs| ±160 µs |
|
||
| Min bits | 35 | (variable) |
|
||
|
||
## Encoding
|
||
|
||
PWM; preamble: two short then alternating short/long.
|
||
|
||
## Frame Layout (variable)
|
||
|
||
- **51-bit format:** serial (28) | button (4) | counter (16) — “MAGIC CODE” / Dynamic; parsed for serial/btn/cnt.
|
||
- Other lengths (35, 57, 63, 64, 81, 82) decoded as raw bit count but not field-parsed.
|
||
|
||
## Decoder Steps
|
||
|
||
1. **Reset** — Wait for preamble (2 short + alternating).
|
||
2. **CheckPreamble** — Confirm preamble pattern.
|
||
3. **SaveDuration** — Store pulse duration.
|
||
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).
|
||
|
||
## Encoder
|
||
|
||
Not implemented (no encoder in reference).
|
||
|
||
## Frequencies
|
||
|
||
433.92 MHz.
|