typedef enum statement confusion.

[Daniel.Blesener]

Hey all, thanks for the help. This should be fairly easy for someone who understands this syntax well. I am modifying some code for work, but ran into a little confusion with the statement below, cannot find what i need online. I understand typedef and enum alone, but the syntax here is throwing me off. Doesn't enum need a declaration of a variable name after it, before the list? And does typedef before enum cause each on to be an individual variable type? Either case does not make much sense. I just two statements of code with this syntax usage, but it appears much more so it is vital that I know what is going on. Thanks much.

typedef enum {
  CLK_PRESCALER_HSIDIV1   = (u8)0x00, /*!< High speed internal clock prescaler: 1 */
  CLK_PRESCALER_HSIDIV2   = (u8)0x08, /*!< High speed internal clock prescaler: 2 */
  CLK_PRESCALER_HSIDIV4   = (u8)0x10, /*!< High speed internal clock prescaler: 4 */
  CLK_PRESCALER_HSIDIV8   = (u8)0x18, /*!< High speed internal clock prescaler: 8 */
  CLK_PRESCALER_CPUDIV1   = (u8)0x80, /*!< CPU clock division factors 1 */
  CLK_PRESCALER_CPUDIV2   = (u8)0x81, /*!< CPU clock division factors 2 */
  CLK_PRESCALER_CPUDIV4   = (u8)0x82, /*!< CPU clock division factors 4 */
  CLK_PRESCALER_CPUDIV8   = (u8)0x83, /*!< CPU clock division factors 8 */
  CLK_PRESCALER_CPUDIV16  = (u8)0x84, /*!< CPU clock division factors 16 */
  CLK_PRESCALER_CPUDIV32  = (u8)0x85, /*!< CPU clock division factors 32 */
  CLK_PRESCALER_CPUDIV64  = (u8)0x86, /*!< CPU clock division factors 64 */
  CLK_PRESCALER_CPUDIV128 = (u8)0x87  /*!< CPU clock division factors 128 */
} CLK_Prescaler_TypeDef;

/**
   * @brief  SWIM Clock divider.
   */
typedef enum {
  CLK_SWIMDIVIDER_2 = (u8)0x00, /*!< SWIM clock is divided by 2 */
  CLK_SWIMDIVIDER_OTHER = (u8)0x01 /*!< SWIM clock is not divided by 2 */
}CLK_SWIMDivider_TypeDef;

[laserlight]

Doesn't enum need a declaration of a variable name after it, before the list?

I think you mean the enumeration name rather than a variable name. The answer is no: the enumeration is anonymous, but...

does typedef before enum cause each on to be an individual variable type?

... the typedef gives the enumeration a name, e.g., CLK_Prescaler_TypeDef. So yes, it is a type name.

[itCbitC]

Hey all, thanks for the help. This should be fairly easy for someone who understands this syntax well. I am modifying some code for work, but ran into a little confusion with the statement below, cannot find what i need online. I understand typedef and enum alone, but the syntax here is throwing me off. Doesn't enum need a declaration of a variable name after it, before the list?

That's technically referred to as a tag and is optional.

And does typedef before enum cause each on to be an individual variable type?

Yep!

[Daniel.Blesener]

Thanks for the quick replies! I still do not understand what

CLK_Prescaler_TypeDef; means though? Does it need to be there? All the statements like this have something at the end similar. Why does the statement have CLK_Prescaler_TypeDef; written outside of the parenthesis? Thanks!

[itCbitC]

Thanks for the quick replies! I still do not understand what

CLK_Prescaler_TypeDef;

means though?

It's just a name for the new type you have created. Consider this:

typedef enum {small, medium, large} size;  /* now size is a new name for "enum {small, medium, large}" */
size dimension;  /* makes dimension a variable of type size aka enum {small, medium, large} */