Group dxl2_protocol¶

CRC-16, incremental stream parser and packet encoder with byte stuffing. More...

Classes¶

Type	Name
struct	dxl2_packet One decoded Protocol 2.0 packet.
struct	dxl2_parser Incremental parser state for a byte stream.

Public Functions¶

Type	Name
uint16_t	dxl2_crc16 (const uint8_t * data, size_t length) Calculate the Protocol 2.0 CRC-16 checksum.
int	dxl2_encode (uint8_t id, uint8_t instruction, const uint8_t * parameters, uint16_t parameter_length, uint8_t * output, size_t output_capacity, size_t * output_length) Encode a Protocol 2.0 packet, adding byte stuffing and CRC.
int	dxl2_parser_feed (struct dxl2_parser * parser, uint8_t byte, struct dxl2_packet * packet) Feed one byte to the incremental packet parser.
void	dxl2_parser_init (struct dxl2_parser * parser) Reset a parser before starting or restarting a byte stream.

Macros¶

Type	Name
define	DXL2_MAX_PARAMETER_SIZE `([DXL2\_MAX\_PACKET\_SIZE](group__dxl2__config.md#define-dxl2_max_packet_size) - 10U)` Maximum unstuffed parameter payload size supported by this implementation.
define	DXL2_PARSE_ERROR `(-1)` Error returned for invalid input, malformed packets, or insufficient capacity.

Detailed Description¶

** **

CRC: dxl2_crc16.
Parser: dxl2_parser_init, dxl2_parser_feed.
Encoder: dxl2_encode.

Public Functions Documentation¶

function dxl2_crc16¶

Calculate the Protocol 2.0 CRC-16 checksum.

uint16_t dxl2_crc16 (
    const uint8_t * data,
    size_t length
)

Uses polynomial 0x8005 and an initial CRC value of zero.

Parameters:

data Bytes covered by the CRC.
length Number of bytes to process.

Returns:

Calculated 16-bit CRC; 0 (the initial value) when data is NULL.

function dxl2_encode¶

Encode a Protocol 2.0 packet, adding byte stuffing and CRC.

int dxl2_encode (
    uint8_t id,
    uint8_t instruction,
    const uint8_t * parameters,
    uint16_t parameter_length,
    uint8_t * output,
    size_t output_capacity,
    size_t * output_length
)

Parameters:

id Packet ID.
instruction Instruction byte.
parameters Unstuffed parameter bytes, or NULL when the length is zero.
parameter_length Number of parameter bytes.
output Destination buffer for the complete wire packet.
output_capacity Capacity of output in bytes.
output_length Receives the encoded packet length on success.

Return value:

0 Packet encoded successfully.
DXL2_PARSE_ERROR Invalid input or insufficient output capacity.

function dxl2_parser_feed¶

Feed one byte to the incremental packet parser.

int dxl2_parser_feed (
    struct dxl2_parser * parser,
    uint8_t byte,
    struct dxl2_packet * packet
)

The parser searches for the Protocol 2.0 header, waits for the declared packet length, validates CRC, then removes byte stuffing. Continue feeding bytes after a parse error so the parser can find the next packet header.

Parameters:

parser Parser state.
byte Next byte from the input stream.
packet Output packet; its contents are valid only when the call returns 1.

Return value:

1 A complete valid packet is available in packet.
0 More bytes are required.
DXL2_PARSE_ERROR Invalid arguments or a malformed/CRC-invalid packet.

function dxl2_parser_init¶

Reset a parser before starting or restarting a byte stream.

void dxl2_parser_init (
    struct dxl2_parser * parser
)

Parameters:

parser Parser state to initialize; NULL is ignored.

Macro Definition Documentation¶

define DXL2_MAX_PARAMETER_SIZE¶

Maximum unstuffed parameter payload size supported by this implementation.

#define DXL2_MAX_PARAMETER_SIZE `( DXL2_MAX_PACKET_SIZE - 10U)`

define DXL2_PARSE_ERROR¶

Error returned for invalid input, malformed packets, or insufficient capacity.

#define DXL2_PARSE_ERROR `(-1)`