Use of .c or .h files

[tensaisakuragi06]

Hi, I am curious one thing when using the HAL libraries. Just as an basic exapmle i assign LED1 to PB12 pin of STM32F070CBT6 as an GPIO_output. And i want to use HAL_GPIO_WritePin(GPIOB, LED1, LED1_SET); instead of HAL_GPIO_WritePin(GPIOB, GPIO_PIN_12, GPIO_PIN_SET); . Do you think it is weird that i want to use my variables like that with HAL libraries? Second thing is (if it is not weir or inappropriate), should i define my definitions as "definitions.c" or "definitions.h"? When i make some search, .c file is not recommended. I am not sure if i do all these steps with my ST microcontroller and it works well.

[TDK]

> Do you think it is weird that i want to use my variables like that with HAL libraries?

A bit. The intended usage is something like:

HAL_GPIO_WritePin(LED1_PORT, LED1_PIN, GPIO_PIN_SET);

Your usage mixes this with LED1_SET. But up to you.

> should i define my definitions as "definitions.c" or "definitions.h"?

They will need to be in a header file if you want to use them in multiple source files. If you're only using them within a single source file, you can put them in that source file. Up to you.

[Andrew Neil]

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@tensaisakuragi06 wrote:

i want to use HAL_GPIO_WritePin(GPIOB, LED1, LED1_SET); instead of HAL_GPIO_WritePin(GPIOB, GPIO_PIN_12, GPIO_PIN_SET); . Do you think it is weird that i want to use my variables like that with HAL libraries? .

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Of course not!

That is exactly what CubeMX does with its generated code, and what many ST BSPs (Board Support Packages) do, too.

HAL_GPIO_WritePin is just a C function - its parameters work exactly the same as any other C function.

BTW: note that it is usual practice for ALL CAPITALS names in C to be reserved for #defined names - not variables.

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@tensaisakuragi06 wrote:

should i define my definitions as "definitions.c" or "definitions.h"? .

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You can name your source files however you like!

But you need to understand the C rules of scope & visibility - this is standard C, and nothing specifically to do with STM32.

When you say "definitions", are you talking about preprocessor definitions (using #define), or C functions & variables?

With functions & variables, be sure to understand the difference between declarations and definitions:

https://community.st.com/t5/stm32cubeide-mcus/adding-new-c-source-files-to-my-project-and-navigating-through/m-p/657455/highlight/true#M25847

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@tensaisakuragi06 wrote:

 When i make some search, .c file is not recommended.

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Please provide examples - you may be misunderstanding.

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@tensaisakuragi06 wrote:

I am not sure if i do all these steps with my ST microcontroller and it works well.

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This is all standard C stuff - nothing specifically to do with ST or even microcontrollers.

Here are some C learning & reference materials:

https://blog.antronics.co.uk/2011/08/08/so-youre-thinking-of-starting-with-c/

[Andrew Neil · Accepted solution]

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@TDK wrote:

Your usage mixes this with LED1_SET. But up to you.

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It can be a good thing to define your own LED_SET and LED_CLEAR (or whatever)  - this allows you to be independent of whether the LED is active-high or active-low.

Probably better names would be LED_ON and LED_OFF - which directly indicate the intended function, rather than hiding between the rather ambiguous "set" and "reset"...

[tensaisakuragi06]

I define them with header file format (.h). It works for now. Thank yu for your pointers.

[tensaisakuragi06]

Yeah, it stil confuses me sometimes, i am planing to use both #define 's and variable definitions like unsigned int16 ... ;

According to your pointers, i should seperate them like "declarations for #define 's " and "definitions for unsigned int16 ... ; " like. I hope that i understand you correctly :) .

[Andrew Neil]

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@tensaisakuragi06 wrote:

I define them with header file format (.h).

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That doesn't really make sense - a header (.h) file has no "format" different from a .c file.

The difference is in the way they are used - not their "format".

[tensaisakuragi06]

// Pin definitions
#define LED1 GPIO_PIN_12
#define LED2 GPIO_PIN_3
#define ROLE1 GPIO_PIN_7
#define ROLE2 GPIO_PIN_6
#define BUTON1 GPIO_PIN_13
#define BUTON2 GPIO_PIN_14
#define BUTON3 GPIO_PIN_15


// Macro definitions
#define LED1_ON GPIO_PIN_SET
#define LED1_OFF GPIO_PIN_RESET

#define ROLE1_ON GPIO_PIN_SET
#define ROLE1_OFF GPIO_PIN_RESET

#define LED2_ON GPIO_PIN_SET
#define LED2_OFF GPIO_PIN_RESET

#define ROLE2_ON GPIO_PIN_SET
#define ROLE2_OFF GPIO_PIN_RESET

#define BUTON1_ON GPIO_PIN_SET
#define BUTON1_OFF GPIO_PIN_RESET

#define BUTON2_ON GPIO_PIN_SET
#define BUTON2_OFF GPIO_PIN_RESET

#define BUTON3_ON GPIO_PIN_SET
#define BUTON3_OFF GPIO_PIN_RESET

[tensaisakuragi06]

I change my definitions like above and its looks good for me. If i can improve my logic, please do not hesitate to tell me.

[Andrew Neil]

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@tensaisakuragi06 wrote:

According to your pointers, i should seperate them like "declarations for #define 's " and "definitions for unsigned int16 ... ; " like. I hope that i understand you correctly :) .

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I'm afraid not.

#define is used by the preprocessor; it is purely text substitution. It never gets seen by the compiler proper.

Definitions for functions & variables are what actually create the objects (data or code) in memory. The C programming language requires that each functions & variable must have exactly one definition.

Having more than one definition of a function or variable is an error - you will get an error message saying, "multiple definitions".

Declarations for functions & variables do not cause any memory to be allocated, or code created - they simply give enough information for the function/variable to be used, on the assumption that it has been defined somewhere else.

Again, this is all standard C stuff - nothing specific to ST or embedded or microcontrollers - so see general C programming tutorials, textbooks, etc for details.