Understanding C code

Sam12

Prodigy 30 points

This is a piece of code

epwm_info->EPwm_CMPB_Direction == EPWM_CMP_UP

What does '->' mean here?

over 13 years ago

0 quark over 13 years ago

Expert 2220 points

epwm_info is probably a pointer to a structure. When accessing a field in structure when you are doing it from a _pointer_, you use the (->) instead of a (.)

For example

typedef struct

  int a, b;

} My_struct_type;

My_struct_type a_struct;

My_struct_type *a_struct_pointer = &a_struct;

a_struct.a = 1;

a_struct_pointer->b = 2;

0 Andy Neil over 13 years ago

Guru 35595 points

samir hazra said:
What does '->' mean here?

Exactly the same as it means anywhere else!

This is basic textbook stuff - nothing specifically to do with TI or the C2000: '->' is the 'C' operator for accessing a stucture element from a pointer.

Here are some 'C' learning & reference resources: http://blog.antronics.co.uk/2010/12/12/things-you-shouldve-learned-in-c-class-0-introduction/

0 Sam12 over 13 years ago in reply to quark

Prodigy 30 points

Thanks a lot.....

0 Sam12 over 13 years ago in reply to Sam12

Prodigy 30 points

A portaion of C-code is..

struct ADCTRL1_BITS { // bits description
Uint16 rsvd1:4; // 3:0 reserved
Uint16 SEQ_CASC:1; // 4 Cascaded sequencer mode
Uint16 SEQ_OVRD:1; // 5 Sequencer override
Uint16 CONT_RUN:1; // 6 Continuous run

What is the meaning of declaration ..... Uint16 rsvd1:4?? does it assign 4 to rsvd1?

I know this is a trivial question but i am not an expert in C. so bear with me for this silly question...

0 congqian xu over 13 years ago in reply to Sam12

Prodigy 10 points

not assign 4 to rsvd1.

It defines 4 bits of the ADCTRL1 register, which are reserved for the producer.

0 Andy Neil over 13 years ago in reply to Sam12

Guru 35595 points

Sam12 said:
I know this is a trivial question but i am not an expert in C.

So you really need to be looking into your 'C' textbooks!

You already have a list of 'C' reference and learning resources: http://blog.antronics.co.uk/2010/12/12/things-you-shouldve-learned-in-c-class-0-introduction/

Sam12 said:
so bear with me for this silly question

People aren't going to continue answering your basic questions forever - you need to put in the study & effort to learn the 'C' language if you're going to use it...

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Understanding C code