the uVision complained that: stm32f0xx_i2c_cpal_hal.c(121): error: #20: identifier "I2C2_IRQn" is undefined, however, this is defined in the "stm32f0xx.h" and the header file stm32f0xx_i2c_cpal_hal.h already included the file "stm32f0xx.h". Looked like the compiler cannot recognize the definition in the looping include file.