protocol.h File Reference

Shared C2P-ARQ protocol definitions for SH2SC-EDT (Receiver Node B). More...

#include <stdint.h>

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Data Structures
struct	HelloPacket
	Session-open handshake packet (FLAG_SYN). More...
struct	DataPacket
	Authenticated data packet (FLAG_DAT) and session-close packet (FLAG_FIN). More...

Variables
const uint8_t	MASTER_PSK [32]
	256-bit (32-byte) Pre-Shared Master Key for ChaCha20-Poly1305 AEAD.
const uint8_t	FLAG_SYN = 0x01
	Session open — HelloPacket carrying the 12-byte CSPRNG nonce.
const uint8_t	FLAG_DAT = 0x02
	Data frame — DataPacket carrying an encrypted note (index + duration).
const uint8_t	FLAG_FIN = 0x04
	Session close — instructs RX to teardown the current session.
const uint8_t	HELLO_NONCE_SIZE = 12u
	ChaCha20 IV length in bytes (IETF 96-bit nonce format).
const uint8_t	AUTH_TAG_SIZE = 16u
	Full Poly1305 tag length in bytes (computed internally, not fully transmitted).
const uint8_t	TRUNCATED_MAC_SIZE = 8u
	Bytes of Poly1305 MAC actually placed on the wire (first 8 of 16).
const uint8_t	DATA_PAYLOAD_SIZE = 4u
	Byte size of the encrypted payload in a DataPacket.
const uint8_t	SYNC_BYTE_1 = 0xAA
	First synchronisation byte (preamble marker).
const uint8_t	SYNC_BYTE_2 = 0x55
	Second synchronisation byte (preamble marker).
const uint8_t	ACK_BYTE = 0x06
	Positive acknowledgement — MAC verified, note played (or FIN accepted).
const uint8_t	NACK_BYTE = 0x15
	Negative acknowledgement — MAC mismatch; TX must retransmit.
const uint8_t	REST_INDEX = 255
	Special note index value representing a rest (silence).
const uint32_t	ACK_TIMEOUT_MS = 50UL
	Maximum milliseconds TX waits for an ACK before retransmitting.
const uint8_t	MAX_RETRIES = 50u
	Retransmission limit per packet; exhausting this triggers suspendSession().
const uint16_t	BAUD_RATE = 9600
	UART baud rate in bps (8N1). Chosen for clear bit-width visibility on SimulIDE oscilloscope.

Detailed Description

Shared C2P-ARQ protocol definitions for SH2SC-EDT (Receiver Node B).

Part of the SH2SC-EDT project. Implements the C2P-ARQ protocol. Contains the Pre-Shared Key, frame flag constants, packed packet structs (HelloPacket, DataPacket), ARQ timing constants, and UART configuration shared by both Transmitter and Receiver nodes. Included from receiver.h; do NOT include directly from .ino.

Definition in file protocol.h.