Configuration¶

Build-time parameters live in inc/dxl2_config.h. Each one is guarded by #ifndef, so override it with a compiler definition instead of editing the file:

target_compile_definitions(dxl2 PUBLIC DXL2_MAX_PACKET_SIZE=1024U)

Parameter	Default	Meaning
`DXL2_MAX_PACKET_SIZE`	`256U`	Largest complete wire packet (header to CRC) the parser and encoder accept; `10U..65542U`, checked at compile time

Derived values:

Macro	Value
`DXL2_MAX_PARAMETER_SIZE`	`DXL2_MAX_PACKET_SIZE - 10U`

Memory footprint¶

DXL2_MAX_PACKET_SIZE sizes three buffers:

Object	Size
`struct dxl2_parser`	`DXL2_MAX_PACKET_SIZE` + `size_t`
`struct dxl2_packet`	`DXL2_MAX_PARAMETER_SIZE` + 4 bytes
`struct dxl2_link`	parser + packet + configuration + two counters
`dxl2_link_send()` stack	`DXL2_MAX_PACKET_SIZE`
`dxl2_link_send_status()` stack	`DXL2_MAX_PARAMETER_SIZE` + the `dxl2_link_send()` frame

Stack usage¶

The library does not recurse and does not use variable-length arrays, so the stack depth is fixed. Measured with -fstack-usage, default DXL2_MAX_PACKET_SIZE (256), bytes per function frame:

Function	Cortex-M4 `-Os`	Cortex-M4 `-O0`	x86-64 `-O2`
`dxl2_link_send_status()`	272	296	336
`dxl2_link_send()`	296	312	368
`dxl2_encode()`	24	56	32
`dxl2_crc16()`	8	32	8
`dxl2_link_receive()`	24	32	80
`dxl2_parser_feed()` (with `dxl2_decode_packet()`)	32	32 + 56	80
`dxl2_link_init()`	16	32	48
other functions	0	16	8

Toolchains: Arm GNU Toolchain 15.2 (-mcpu=cortex-m4 -mthumb), GCC 14.2. At -O0 the small static functions (dxl2_get_u16(), dxl2_parser_reset()) add 16 bytes each where they are called.

Worst-case call chains on Cortex-M4 -Os, without the callbacks:

Path	Chain	Stack
Transmit	`dxl2_link_send_status` → `dxl2_link_send` → `dxl2_encode` → `dxl2_crc16`	600 B + `write` callback
Receive	`dxl2_link_receive` → `dxl2_parser_feed` → `dxl2_crc16`	64 B + packet handler
Receive and reply	`dxl2_link_receive` → handler → transmit chain	624 B + handler + `write`

The two large frames are the transmit buffers, so they scale with DXL2_MAX_PACKET_SIZE: about 2 × DXL2_MAX_PACKET_SIZE + 90 bytes for the transmit chain. Measure your own build with:

arm-none-eabi-gcc -mcpu=cortex-m4 -mthumb -Os -std=c11 -fstack-usage -Iinc -I. -c src/dxl2_link.c src/dxl2_protocol.c
cat *.su

CMake options¶

Option	Default	Meaning
`DXL2_UNIT_TESTS`	`OFF`	Build the GoogleTest suite and the `coverage` target
`DXL2_INTEGRATION_TESTS`	`OFF`	Register the pytest suite with CTest
`DXL2_MISRA_RULE_TEXTS`	empty	MISRA C:2012 rule texts file for the `misra-analyze` target
`DXL2_EXAMPLES`	`OFF`	Build the host examples (`examples/`) and register the bare-metal simulation with CTest
`DXL2_COVERAGE_MIN`	`100`	Line and branch coverage (%) below which the `coverage` target fails
`DXL2_MISRA_FAIL_ON_VIOLATION`	`ON`	Make `misra-analyze` fail when the report has a violation