📦 pcobs

postcard + crc + cobs = structured data over anything

no_std • zero-allocation • embedded-ready

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💡 Why?

You've got structs. You need to send them over UART/TCP/USB/whatever.

pcobs gives you:

• 📝 postcard — compact serde serialization, no_std friendly
• 🔐 CRC-16 — catch corrupted packets
• 🧱 COBS framing — zero-byte delimiters, no escaping hell
• 💾 Zero allocations — stack-only, no Vec/Box/HashMap
• ⚡ no_std — works on bare-metal, no OS required

Two functions. That's it.

let len = serialize(&my_struct, &mut buf)?;
let my_struct = deserialize::<MyStruct>(&mut buf, len)?;

---

🚀 Quick Start

[dependencies]
pcobs = "1"
serde = { version = "1", features = ["derive"] }

use pcobs::{serialize, deserialize};
use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize)]
struct SensorData {
    id: u8,
    value: f32,
    flags: u16,
}

// Sender
let data = SensorData { id: 1, value: 23.5, flags: 0xABCD };
let mut buf = [0u8; 256];
let len = serialize(&data, &mut buf)?;
stream.write_all(&buf[..len])?;
stream.write_all(&[0x00])?; // COBS delimiter

// Receiver
let mut buf = [0u8; 256];
let n = read_until_delimiter(stream, &mut buf)?;
let decoded: SensorData = deserialize(&mut buf, n)?;

---

📐 Packet Format

┌────────────────────────────────────────┬──────┐
│ Payload                     │ CRC-16   │ 0x00 │
│ postcard(your data)         │ checksum │      │
│────────────────────────────────────────│      │
│ COBS frame                             │ delim│
│ no zeros in encoded data               │      │
└────────────────────────────────────────┴──────┘

Steps:

1. Serialize your struct with postcard
2. Append CRC-16 checksum (2 bytes)
3. COBS-encode the whole thing
4. Send over your transport, appending a 0x00 delimiter

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📏 Buffer Math

Encoding is done in-place - no buffer splitting needed. COBS adds minimal overhead (at most 1 byte per 254 bytes), plus 2 bytes for CRC.

Buffer	Max Payload
64 B	~60 B
256 B	~252 B
512 B	~508 B
1024 B	~1018 B

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🛠️ Transport Agnostic

Works over anything that moves bytes:

• 📡 UART / Serial
• 🌐 TCP sockets
• 🔌 USB bulk endpoints
• 📻 Radio (LoRa, BLE, etc.)
• 🧪 Pipes / files for testing

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⚡ Features

• no_std — works on bare-metal, no OS required
• Zero allocations — stack-only, no heap, embedded-friendly
• serde — derive your structs
• Single-pass encoding
• In-place decoding