.\STM32F1x4463.axf: Error: L6218E: Undefined symbol BEEP_Init (referred from main.o).
.\STM32F1x4463.axf: Error: L6218E: Undefined symbol SPI2_Init (referred from main.o).
.\STM32F1x4463.axf: Error: L6218E: Undefined symbol SPI2_ReadWriteByte (referred from radio_comm.o).