GPCRC - General Purpose CRC

Description

General Purpose Cyclic Redundancy Check (GPCRC) API.

The GPCRC API functions provide full support for the GPCRC peripheral.

The GPCRC module is a peripheral that implements a Cyclic Redundancy Check (CRC) function. It supports a fixed 32-bit polynomial and a user configurable 16-bit polynomial. The fixed 32-bit polynomial is the commonly used IEEE 802.3 polynomial 0x04C11DB7.

When using a 16-bit polynomial it is up to the user to choose a polynomial that fits the application. Commonly used 16-bit polynomials are 0x1021 (CCITT-16), 0x3D65 (IEC16-MBus), and 0x8005 (ZigBee, 802.15.4, and USB). See this link for other polynomials: https://en.wikipedia.org/wiki/Cyclic_redundancy_check

Before a CRC calculation can begin it is important to call the GPCRC_Start function. This function will reset CRC calculation by copying the configured initialization value over to the CRC data register.

There are two ways of sending input data to the GPCRC. Either write the input data into the input data register using input functions GPCRC_InputU32 , GPCRC_InputU16 and GPCRC_InputU8 , or the user can configure LDMA - Linked DMA to transfer data directly to one of the GPCRC input data registers.

Examples of GPCRC usage:

A CRC-32 Calculation:

#if !defined(_SILICON_LABS_32B_SERIES_2)
/* The GPCRC is a high frequency peripheral so we need to enable the
* HFPER clock in addition to the GPCRC clock. */
CMU_ClockEnable ( cmuClock_HFPER , true );
CMU_ClockEnable ( cmuClock_GPCRC , true );
#endif
uint32_t checksum;
/* Initialize GPCRC, 32-bit fixed polynomial is default */
GPCRC_Init_TypeDef init = GPCRC_INIT_DEFAULT ;
init. initValue = 0xFFFFFFFF; // Standard CRC-32 init value
GPCRC_Init (GPCRC, &init);
GPCRC_Start (GPCRC);
GPCRC_InputU8 (GPCRC, 0xC5);
/* According to the CRC-32 specification, the end result should be inverted */
checksum = ~ GPCRC_DataRead (GPCRC);
/* The checksum is now 0x390CD9B2 */

A CRC-16 Calculation:

#if !defined(_SILICON_LABS_32B_SERIES_2)
/* The GPCRC is a high frequency peripheral so we need to enable the
* HFPER clock in addition to the GPCRC clock. */
CMU_ClockEnable ( cmuClock_HFPER , true );
CMU_ClockEnable ( cmuClock_GPCRC , true );
#endif
uint16_t checksum;
/* Initialize GPCRC with the 16-bit polynomial 0x8005. */
GPCRC_Init_TypeDef init = GPCRC_INIT_DEFAULT ;
init. crcPoly = 0x8005;
GPCRC_Init (GPCRC, &init);
GPCRC_Start (GPCRC);
GPCRC_InputU8 (GPCRC, 0xAB);
checksum = (uint16_t) GPCRC_DataRead (GPCRC);
/* The checksum is now 0xBF41 */

A CRC-CCITT calculation:

#if !defined(_SILICON_LABS_32B_SERIES_2)
/* The GPCRC is a high frequency peripheral so we need to enable the
* HFPER clock in addition to the GPCRC clock. */
CMU_ClockEnable ( cmuClock_HFPER , true );
CMU_ClockEnable ( cmuClock_GPCRC , true );
#endif
/* Initialize GPCRC with the 16-bit CRC-CCIT polynomial 0x1021 and use
* the inital value of 0xFFFF. */
GPCRC_Init_TypeDef init = GPCRC_INIT_DEFAULT ;
init. crcPoly = 0x1021;
init. initValue = 0xFFFF;
init. reverseBits = true ;
GPCRC_Init (GPCRC, &init);
char * input = "123456789" ;
GPCRC_Start (GPCRC);
for ( size_t i = 0; i < strlen(input); i++) {
GPCRC_InputU8 (GPCRC, (uint8_t) input[i]);
}
uint16_t checksum = (uint16_t) GPCRC_DataReadBitReversed (GPCRC);
/* checksum is now 0x29B1 */

Data Structures

struct GPCRC_Init_TypeDef
CRC initialization structure.

Functions

void GPCRC_Init (GPCRC_TypeDef *gpcrc, const GPCRC_Init_TypeDef *init)
Initialize the General Purpose Cyclic Redundancy Check (GPCRC) module.
void GPCRC_Reset (GPCRC_TypeDef *gpcrc)
Reset GPCRC registers to the hardware reset state.
void GPCRC_Enable (GPCRC_TypeDef *gpcrc, bool enable)
Enable/disable GPCRC.
void GPCRC_Start (GPCRC_TypeDef *gpcrc)
Issues a command to initialize CRC calculation.
void GPCRC_InitValueSet (GPCRC_TypeDef *gpcrc, uint32_t initValue)
Set the initialization value of the CRC.
void GPCRC_InputU32 (GPCRC_TypeDef *gpcrc, uint32_t data)
Writes a 32-bit value to the input data register of the CRC.
void GPCRC_InputU16 (GPCRC_TypeDef *gpcrc, uint16_t data)
Writes a 16-bit value to the input data register of the CRC.
void GPCRC_InputU8 (GPCRC_TypeDef *gpcrc, uint8_t data)
Writes an 8-bit value to the input data register of the CRC.
uint32_t GPCRC_DataRead (GPCRC_TypeDef *gpcrc)
Reads the data register of the CRC.
uint32_t GPCRC_DataReadBitReversed (GPCRC_TypeDef *gpcrc)
Reads the data register of the CRC bit reversed.
uint32_t GPCRC_DataReadByteReversed (GPCRC_TypeDef *gpcrc)
Reads the data register of the CRC byte reversed.

Macros

#define GPCRC_INIT_DEFAULT
Default configuration for GPCRC_Init_TypeDef structure.

Function Documentation

◆ GPCRC_Init()

void GPCRC_Init ( GPCRC_TypeDef * gpcrc,
const GPCRC_Init_TypeDef * init
)

Initialize the General Purpose Cyclic Redundancy Check (GPCRC) module.

Use this function to configure the operational parameters of the GPCRC, such as the polynomial to use and how the input should be preprocessed before entering the CRC calculation.

Note
This function will not copy the initialization value to the data register to prepare for a new CRC calculation. Either call GPCRC_Start before each calculation or by use the autoInit functionality.
Parameters
[in] gpcrc A pointer to the GPCRC peripheral register block.
[in] init A pointer to the initialization structure used to configure the GPCRC.

◆ GPCRC_Reset()

void GPCRC_Reset ( GPCRC_TypeDef * gpcrc )

Reset GPCRC registers to the hardware reset state.

Note
The data registers are not reset by this function.
Parameters
[in] gpcrc A pointer to the GPCRC peripheral register block.

◆ GPCRC_Enable()

void GPCRC_Enable ( GPCRC_TypeDef * gpcrc,
bool enable
)
inline

Enable/disable GPCRC.

Parameters
[in] gpcrc Pointer to GPCRC peripheral register block.
[in] enable True to enable GPCRC, false to disable.

◆ GPCRC_Start()

void GPCRC_Start ( GPCRC_TypeDef * gpcrc )
inline

Issues a command to initialize CRC calculation.

Issues the command INIT in GPCRC_CMD that initializes CRC calculation by writing the initial values to the DATA register.

Parameters
[in] gpcrc Pointer to GPCRC peripheral register block.

◆ GPCRC_InitValueSet()

void GPCRC_InitValueSet ( GPCRC_TypeDef * gpcrc,
uint32_t initValue
)
inline

Set the initialization value of the CRC.

Parameters
[in] initValue Value to use to initialize a CRC calculation. This value is moved into the data register when calling GPCRC_Start
[in] gpcrc Pointer to GPCRC peripheral register block.

◆ GPCRC_InputU32()

void GPCRC_InputU32 ( GPCRC_TypeDef * gpcrc,
uint32_t data
)
inline

Writes a 32-bit value to the input data register of the CRC.

Use this function to write a 32-bit input data to the CRC. CRC calculation is based on the provided input data using the configured CRC polynomial.

Parameters
[in] gpcrc Pointer to GPCRC peripheral register block.
[in] data Data to be written to the input data register.

◆ GPCRC_InputU16()

void GPCRC_InputU16 ( GPCRC_TypeDef * gpcrc,
uint16_t data
)
inline

Writes a 16-bit value to the input data register of the CRC.

Use this function to write a 16 bit input data to the CRC. CRC calculation is based on the provided input data using the configured CRC polynomial.

Parameters
[in] gpcrc Pointer to GPCRC peripheral register block.
[in] data Data to be written to the input data register.

◆ GPCRC_InputU8()

void GPCRC_InputU8 ( GPCRC_TypeDef * gpcrc,
uint8_t data
)
inline

Writes an 8-bit value to the input data register of the CRC.

Use this function to write an 8-bit input data to the CRC. CRC calculation is based on the provided input data using the configured CRC polynomial.

Parameters
[in] gpcrc Pointer to GPCRC peripheral register block.
[in] data Data to be written to the input data register.

◆ GPCRC_DataRead()

uint32_t GPCRC_DataRead ( GPCRC_TypeDef * gpcrc )
inline

Reads the data register of the CRC.

Use this function to read the calculated CRC value.

Parameters
[in] gpcrc Pointer to GPCRC peripheral register block.
Returns
Content of the CRC data register.

◆ GPCRC_DataReadBitReversed()

uint32_t GPCRC_DataReadBitReversed ( GPCRC_TypeDef * gpcrc )
inline

Reads the data register of the CRC bit reversed.

Use this function to read the calculated CRC value bit reversed. When using a 32-bit polynomial, bits [31:0] are reversed, when using a 16-bit polynomial, bits [15:0] are reversed.

Parameters
[in] gpcrc Pointer to GPCRC peripheral register block.
Returns
Content of the CRC data register bit reversed.

◆ GPCRC_DataReadByteReversed()

uint32_t GPCRC_DataReadByteReversed ( GPCRC_TypeDef * gpcrc )
inline

Reads the data register of the CRC byte reversed.

Use this function to read the calculated CRC value byte reversed.

Parameters
[in] gpcrc Pointer to GPCRC peripheral register block.
Returns
Content of the CRC data register byte reversed.

Macro Definition Documentation

◆ GPCRC_INIT_DEFAULT

#define GPCRC_INIT_DEFAULT
Value:
{ \
0x04C11DB7UL, /* CRC32 Polynomial value. */ \
0x00000000UL, /* Initialization value. */ \
false, /* Byte order is normal. */ \
false, /* Bit order is not reversed on output. */ \
false, /* Disable byte mode. */ \
false, /* Disable automatic initialization on data read. */ \
true, /* Enable GPCRC. */ \
}

Default configuration for GPCRC_Init_TypeDef structure.