crc.c File Reference

CRC16-CCITT implementation. More...

#include "icarus/crc.h"
#include "icarus/config.h"
#include <stddef.h>
#include "icarus/kernel.h"
#include "stm32h7xx.h"

Go to the source code of this file.

Macros
#define	CRC_CR_POLYSIZE_16   (0x1u << CRC_CR_POLYSIZE_Pos)

Functions
static void	crc_hw_init (void)
uint16_t	crc16_ccitt (const uint8_t *data, uint16_t len)
	Compute CRC16-CCITT (poly 0x1021, init 0xFFFF) over a byte buffer.

Variables
static volatile uint8_t	crc_initialised

Detailed Description

CRC16-CCITT implementation.

On STM32H7 target, drives the on-chip CRC peripheral with the CCITT polynomial (0x1021), 16-bit polynomial size, no input reversal, no output reversal, and an initial value of 0xFFFF. The peripheral is lazy-initialised on first call: the CRC clock is enabled on the AHB4 bus and the registers are configured once.

Hardware CRC consumes one AHB cycle per byte and frees the CPU for the duration of the transfer; for the buffer sizes used by the kvstore and table services this is roughly 4× faster than the bytewise software loop.

The peripheral has internal state (the running CRC value), so every public call is wrapped in a critical section to prevent two tasks corrupting each other's computation.

Under HOST_TEST a portable bytewise loop is used so unit tests run unchanged off-target.

Author

Souham Biswas

Date

2026

Copyright

Copyright 2025-2026 Souham Biswas https://github.com/ironhide23586/icarus-os-core Licensed under the Apache License, Version 2.0

Definition in file crc.c.

Macro Definition Documentation

CRC_CR_POLYSIZE_16

#define CRC_CR_POLYSIZE_16   (0x1u << CRC_CR_POLYSIZE_Pos)

Definition at line 47 of file crc.c.

Function Documentation

crc16_ccitt()

uint16_t crc16_ccitt	(	const uint8_t *	data,
		uint16_t	len
	)

Compute CRC16-CCITT (poly 0x1021, init 0xFFFF) over a byte buffer.

Parameters

data	Buffer to checksum (may be NULL only if len is 0).
len	Number of bytes in data.

Returns

The 16-bit CRC value.

Definition at line 66 of file crc.c.

References __enter_critical(), __exit_critical(), crc_hw_init(), and crc_initialised.

Referenced by __cs_add_region(), __cs_check_all(), __cs_rebaseline(), __tbl_activate_prepare(), __tbl_load(), and cs_selftest().

crc_hw_init()

static void crc_hw_init ( void  )

static

Definition at line 51 of file crc.c.

References CRC_CR_POLYSIZE_16, and crc_initialised.

Referenced by crc16_ccitt().

Variable Documentation

crc_initialised

volatile uint8_t crc_initialised

static

Definition at line 49 of file crc.c.

Referenced by crc16_ccitt(), and crc_hw_init().