Low-level driver implementation for the AVR XMEGA AU/B/C Cyclic Redundancy Check (CRC) module.

A cyclic redundancy check (CRC) is an error detection technique test algorithm used to find accidental errors in data, and it is commonly used to determine the correctness of a data transmission, and data present in the data and program memories. The CRC module takes a data stream or a block of data as input and generates a 16- or 32-bit output that can be appended to the data and used as a checksum. When the same data are later received or read, the device or application can either repeat the calculation for the data with the appended checksum, which should result in the checksum zero flag being set. The other option is to calculate the checksum and compare it to the one calculated earlier. If the new CRC result does not match the one calculated earlier or zero, the block contains a data error. The application is then able to the detect this and may take a corrective action, such as requesting the data to be sent again or simply not using the incorrect data. The CRC module in XMEGA devices supports two commonly used CRC polynomials; CRC-16 (CRC-CCITT) and CRC-32 (IEEE 802.3).

Macros
#define	CRC_APP NVM_CMD_APP_CRC_gc
	Perform a CRC calculation on the boot loader section. More...

#define	CRC_BOOT NVM_CMD_BOOT_CRC_gc
	Perform a CRC calculation on the application section. More...

#define	CRC_FLASH_RANGE NVM_CMD_FLASH_RANGE_CRC_gc
	Perform a CRC calculation on an address range in flash. More...

Enumerations
enum	crc_16_32_t { CRC_16BIT, CRC_32BIT }
	Flag to indicate whether DMA is supported. More...

Functions
void	crc16_append_value (uint16_t value, void *ptr)
	Appends a CRC value to the given pointer. More...

void	crc32_append_value (uint32_t value, void *ptr)
	Get and append data to generate checksum zero with CRC32. More...

uint32_t	crc_flash_checksum (NVM_CMD_t crc_type, flash_addr_t flash_addr, uint32_t len)
	Perform a CRC-32 calculation on the entire flash memory, on only the application section, on only the boot section, or on a selectable range of the flash memory. More...

uint32_t	crc_io_checksum (void *data, uint16_t len, enum crc_16_32_t crc_16_32)
	Calculate the CRC checksum for data in a buffer. More...

void	crc_io_checksum_byte_add (uint8_t data)
	Add one byte of data to CRC performed on I/O interface. More...

void	crc_io_checksum_byte_start (enum crc_16_32_t crc_16_32)
	Reset CRC module and set source to I/O interface. More...

uint32_t	crc_io_checksum_byte_stop (void)
	Disable CRC module and return checksum. More...

void	crc_set_initial_value (uint32_t value)
	Set initial CRC value for next CRC calculation. More...

#define CRC_APP NVM_CMD_APP_CRC_gc

Perform a CRC calculation on the boot loader section.

Referenced by crc_flash_checksum().

#define CRC_BOOT NVM_CMD_BOOT_CRC_gc

Perform a CRC calculation on the application section.

Referenced by crc_flash_checksum().

#define CRC_FLASH_RANGE NVM_CMD_FLASH_RANGE_CRC_gc

Perform a CRC calculation on an address range in flash.

Referenced by crc_flash_checksum().

enum crc_16_32_t

Flag to indicate whether DMA is supported.

Enum to indicate whether to use CRC-16 or CRC-32

Enumerator
CRC_16BIT
CRC_32BIT

void crc16_append_value	(	uint16_t	value,
		void *	ptr
	)

Appends a CRC value to the given pointer.

Taking the checksum of the value and the appended data will result in zero.

Note: At least two bytes must be reserved at the given pointer location.

Parameters

value	CRC value to append
ptr	pointer to 2 byte memory location to store value.

Referenced by main().

void crc32_append_value	(	uint32_t	value,
		void *	ptr
	)

Get and append data to generate checksum zero with CRC32.

This function calculates checksum value to append to the data after generating its checksum. The value is written to given pointer as little endian. Taking the checksum of the data appended will result in checksum zero.

Note: At least four bytes must be reserved at the given pointer location.

Parameters

value	the value to convert to append value
ptr	pointer to 4 byte memory location to store the value.

References crc_bit_revert().

Referenced by main().

uint32_t crc_flash_checksum	(	NVM_CMD_t	crc_type,
		flash_addr_t	flash_addr,
		uint32_t	length
	)

Perform a CRC-32 calculation on the entire flash memory, on only the application section, on only the boot section, or on a selectable range of the flash memory.

This function setups the type of CRC to perform and configures the memory range to perform the CRC on, and starts the CRC via the NVM module. When the calculation is done, the function disables the CRC module and returns the checksum. For CRC on the boot or application section, start address and length are not needed.

Note: In the flash range mode, an even number of bytes is read. If the user selects a range with an odd number of bytes, an extra byte will be read, and the checksum will not correspond to the selected range.

Parameters

crc_type	what kind of CRC to do perform on the NVM module: CRC_FLASH_RANGE, CRC_BOOT or CRC_APP
flash_addr	address of first byte in flash to perform CRC on
length	number of bytes to perform CRC on

Returns: checksum CRC-32 checksum

References Assert, crc_32_enable(), CRC_APP, CRC_BOOT, crc_checksum_complete(), CRC_FLASH_RANGE, crc_reset(), crc_set_source(), nvm_issue_command(), and nvm_issue_flash_range_crc().

uint32_t crc_io_checksum	(	void *	data,
		uint16_t	len,
		enum crc_16_32_t	crc_16_32
	)

Calculate the CRC checksum for data in a buffer.

This function initializes the CRC module, calculates the checksum for the selected number of bytes in a data buffer, disables the module and returns the calculated checksum.

Parameters

data	data buffer to perform CRC on
len	the number of bytes to perform CRC on
crc_16_32	enum to indicate whether CRC-32 or CRC-16 shall be used

Returns: checksum checksum

References crc_io_checksum_byte_add(), crc_io_checksum_byte_start(), and crc_io_checksum_byte_stop().

Referenced by main().

void crc_io_checksum_byte_add ( uint8_t data )

Add one byte of data to CRC performed on I/O interface.

This function writes a byte to the DATAIN register. Each time this function is called, the checksum is calculated for the new data appended to all previous data written since the crc_io_checksum_byte_start was called. A new checksum is ready one clock cycle after the DATAIN register is written.

Parameters

data	data to perform CRC on

Referenced by crc_io_checksum().

void crc_io_checksum_byte_start ( enum crc_16_32_t crc_16_32 )

Reset CRC module and set source to I/O interface.

This function initializes the CRC module, and crc_io_checksum_byte_add can be used to add bytes to calculate checksum for. When any number of bytes have been added, the crc_io_checksum_byte_stop can be called to disable the module and get the calculated checksum.

Parameters

crc_16_32 enum to indicate whether CRC-32 or CRC-16 shall be used

References crc_32_enable(), CRC_32BIT, crc_reset(), and crc_set_source().

Referenced by crc_io_checksum().

uint32_t crc_io_checksum_byte_stop ( void )

Disable CRC module and return checksum.

This function stops the CRC calculation for bytes added with the crc_io_checksum_byte_add and returns the calculated checksum.

Return values

checksum checksum

References crc_checksum_complete().

Referenced by crc_io_checksum().

void crc_set_initial_value ( uint32_t value )