CRC_PolynomialUpdate Example Description

How to use the CRC peripheral through the STM32C0xx CRC HAL and LL API. The LL API is used for performance improvement. The CRC calculation unit computes the 8-bit CRC code of a given buffer of 32-bit data words, based on a user-defined generating polynomial. In this example, the polynomial is first set manually to 0x9B (X^8 + X^7 + X^4 + X^3 + X + 1). In a second step, the generating polynomial value and length are updated and set to 0x1021 (X^16 + X^12 + X^5 + 1) for a new CRC calculation. These updates are performed using the CRC LL API.

At the beginning of the main program the HAL_Init() function is called to reset all the peripherals, initialize the Flash interface and the systick. Then the SystemClock_Config() function is used to configure the system clock (SYSCLK).

The CRC peripheral configuration is ensured by HAL_CRC_Init() function. The latter is calling HAL_CRC_MspInit() function which core is implementing the configuration of the needed CRC resources according to the used hardware (CLOCK). You can update HAL_CRC_Init() input parameters to change the CRC configuration.

For each computation, calculated CRC code is stored in uwCRCValue variable. Once calculated, the CRC value (uwCRCValue) is compared to the CRC expected value (uwExpectedCRCValue1 and uwExpectedCRCValue2).

STM32 board LED is used to monitor the example status: - LED4 is ON when correct CRC values are calculated - LED4 is slowly blinking (1 sec. period) when there is an error in initialization or if an incorrect CRC value is calculated.

Notes

  1. Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds) based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower) than the peripheral interrupt. Otherwise the caller ISR process will be blocked. To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.

  2. The example needs to ensure that the SysTick time base is always set to 1 millisecond to have correct HAL operation.

Keywords

Security, CRC, CRC Polynomial, CRC-8-WCDMA, CRC-16-ANSI, hardware CRC, user-defined generating polynomial

Directory contents

Hardware and Software environment

How to use it ?

In order to make the program work, you must do the following: