proto_sizes.h File Reference

Fundamental IO-Homecontrol frame and crypto size constants. More...

#include <cstdint>

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Namespaces
namespace	esphome
namespace	esphome::home_io_control

Variables
static constexpr uint8_t	esphome::home_io_control::NODE_ID_SIZE = 3
	Device/node addresses are 3 bytes (e.g., "123ABC").
static constexpr uint8_t	esphome::home_io_control::NODE_ID_STRING_SIZE = (NODE_ID_SIZE * 2) + 1
	Uppercase hex node ID plus null terminator.
static constexpr uint8_t	esphome::home_io_control::HMAC_SIZE = 6
	Authentication HMAC is 6 bytes (truncated AES output).
static constexpr uint8_t	esphome::home_io_control::AES_KEY_SIZE = 16
	AES-128 key size.
static constexpr uint8_t	esphome::home_io_control::AES_BLOCK_SIZE = 16
	AES block size.
static constexpr uint8_t	esphome::home_io_control::IV_SIZE = 16
	Initialization vector size for AES.
static constexpr uint8_t	esphome::home_io_control::IV_PADDING = 0x55
	Padding byte used in IV construction.
static constexpr uint8_t	esphome::home_io_control::BITS_PER_BYTE = 8
	Number of bits in one protocol byte.
static constexpr uint8_t	esphome::home_io_control::FRAME_MIN_SIZE = 9
	Minimum frame: CTRL0+CTRL1+DST(3)+SRC(3)+CMD(1).
static constexpr uint8_t	esphome::home_io_control::FRAME_MAX_DECLARED_SIZE = 32
	Largest frame length CTRL0's 5-bit length field (bits [4:0], length - 1) can express.
static constexpr uint8_t	esphome::home_io_control::FRAME_MAX_SIZE = FRAME_MAX_DECLARED_SIZE
	Historical name for FRAME_MAX_DECLARED_SIZE, kept as an alias rather than a second literal so the two names can never disagree — most call sites (set_cmd, serialize, parse, every fixed-size frame buffer that only ever holds a declared-length frame) predate the trailer/wire distinction and still read most naturally as "the max frame size".
static constexpr uint8_t	esphome::home_io_control::FRAME_MAX_DATA_SIZE = 23
	Maximum data bytes after command ID (declared length - header).
static constexpr uint8_t	esphome::home_io_control::FRAME_CMD_OFFSET = 8
	Byte offset of the command ID in a raw wire buffer.
static constexpr uint8_t	esphome::home_io_control::FRAME_CRC_SIZE = 2
	Size of the on-air CRC-CCITT trailer appended after every frame (declared bytes, plus the out-of-length MAC trailer when present).
static constexpr uint8_t	esphome::home_io_control::FRAME_MAX_TRAILER_SIZE = HMAC_SIZE
	Largest out-of-length authenticator a frame can carry.
static constexpr uint8_t	esphome::home_io_control::FRAME_MAX_WIRE_SIZE = FRAME_MAX_DECLARED_SIZE + FRAME_MAX_TRAILER_SIZE + FRAME_CRC_SIZE
	Largest number of bytes a buffer must hold to receive or transmit any frame this project knows about, trailer and CRC included: FRAME_MAX_DECLARED_SIZE (what CTRL0 can declare).

Detailed Description

Fundamental IO-Homecontrol frame and crypto size constants.

These sizes are the lowest layer of the protocol model: node-ID widths, AES/HMAC sizes and frame bounds. They live in their own header so the other protocol headers can depend on them without pulling in the full frame API.

Definition in file proto_sizes.h.