when I wrote the instance basic timer interrupt,the keil5 occurred errors:..\..\Output\atk_f103.axf: Error: L6218E: Undefined symbol HAL_TIM_Base_Init (referred from btim.o).

It made me nervous,I didn't know why the errors occurred. After checking the errors and searching some information from the internet，I realized the sourse of the errors.I didn't add all the files in this project.Due to the project required the files 'tm32f1xx_hal_tim_ex.c' and 'stm32f1xx_hal_tim.c',it made the errors.So I tried to add the files.

After that,the keil5 still occurred the error:..\..\Output\atk_f103.axf: Error: L6218E: Undefined symbol HAL_TIM_IRQHandle (referred from btim.o).

I found I missed a letter 'r'.It was pretty bad.After I added the letter I missed ,it was ok.