如何访问另一个结构内的结构字段指针并正确编写？

Question

I have the following structs (from a library I'm using) with some fields and I would like to assign with OR operation a new value. But I'm debugging and I can't see how anything is writing there in stm32l4xx_hal_tim.c file:

 typedef struct
 {
   TIM_TypeDef              *Instance;     /*!< Register base address  */
   TIM_Base_InitTypeDef     Init;          /*!< TIM Time Base required parameters */
   HAL_TIM_ActiveChannel    Channel;       /*!< Active channel                    */
   DMA_HandleTypeDef        *hdma[7];      /*!< DMA Handlers array This array is accessed by a @ref DMA_Handle_index */
   HAL_LockTypeDef          Lock;          /*!< Locking object                    */
   __IO HAL_TIM_StateTypeDef   State;         /*!< TIM operation state               */
 }TIM_HandleTypeDef;


typedef struct
{
  __IO uint32_t CR1;         /*!< TIM control register 1,                   Address offset: 0x00 */
  __IO uint32_t CR2;         /*!< TIM control register 2,                   Address offset: 0x04 */
  __IO uint32_t SMCR;        /*!< TIM slave mode control register,          Address offset: 0x08 */
  __IO uint32_t DIER;        /*!< TIM DMA/interrupt enable register,        Address offset: 0x0C */
  __IO uint32_t SR;          /*!< TIM status register,                      Address offset: 0x10 */
  __IO uint32_t EGR;         /*!< TIM event generation register,            Address offset: 0x14 */
  __IO uint32_t CCMR1;       /*!< TIM capture/compare mode register 1,      Address offset: 0x18 */
  __IO uint32_t CCMR2;       /*!< TIM capture/compare mode register 2,      Address offset: 0x1C */
  __IO uint32_t CCER;        /*!< TIM capture/compare enable register,      Address offset: 0x20 */
  __IO uint32_t CNT;         /*!< TIM counter register,                     
 } TIM_TypeDef;

I have a part of code where I defined: TIM_HandleTypeDef TIMER_Struct;

And I would like to access the field "CR1" of TIM_TypeDef struct that is "*Instance" field of TIM_HandleTypeDef. So I have done it by this way in a function DRV_TIMER_init():

  #include "main.h"
  #include "stm32l4xx_hal_tim.h"

  uint32_t uwPrescalerValue = 0;
  TIM_HandleTypeDef TIMER_Struct;
  void DRV_TIMER_init(void);

 int main(void)
 {  

   DRV_TIMER_init();
   while(1)
   {

   }

 }

 //where uint32_t SystemCoreClock = 4000000; in other system source file.
 void DRV_TIMER_init(void)
 {
  uwPrescalerValue = (uint32_t)(SystemCoreClock / 1000000) - 1;
  TIMER_Struct.Init.Period            = 100 - 1;
  TIMER_Struct.Init.Prescaler         = uwPrescalerValue;
  TIMER_Struct.Init.ClockDivision     = 0; // these accesses work

  TIMER_Struct.Instance -> CR1 |= 0x01 << 3; // this no works

 }

Even if I write directly:

 TIMER_Struct.Instance -> CR1 = 0xFFFFFFFF; 

It stills without having effect.

I think It could be a fact that I'm not controlling appropiately the pointer access or similar. But I don't see how can I access and modify the content of the commented field. Since I can see (debug mode) how the rest of struct fields updates are writen correctly.

Any correction suggested here?

TIMER_Struct.Instance -> CR1 = 0xFFFFFFFF; 

I try different ways to get it with no success. I need new ideas.

Answer 1

I think you forgot to define TIMER_Struct.Instance

TIM_HandleTypeDef TIMER_Struct;
TIMER_Struct.Instance = TIM1;
//Now you can access TIMER_Struct.Instance
TIMER_Struct.Instance->CR1 = (uint32_t)0xFFFFFFFF;

But I prefer to use CMSIS for writing to registers. No need for the HAL. With CMSIS writing to a register could look like:

TIM1->CR1=(uint32_t)0xFFFFFFFF

Answer 2

TIM_TypeDef              *Instance;

is just a pointer which is not pointing to anywhere so you can't dereference it

you have defined somewhere in the lib a macro like this:

#define TIM    (TIM_TypeDef*)0xDEADBEEF;

this is how you map the registers to the memory

try modifying your code like this:

TIMER_Struct.Instance = (TIM_Typedef*)0xDEADBEEF;

or just

TIMER_Struct.Instance = TIM;

than

 TIMER_Struct.Instance -> CR1 |= 0x01 << 3;

should work

Answer 3

I have found the solution. First you must enable the peripheral clock. If not, there won't be any effect over timer registers, because the pointer structs fields were pointing directly to the hardware registers allocation. This was the cause why I can't see any update when watching my struct var at debugging.

I was enabling clk (with hal_xxx_init()) after writing to the allocation. That was my mistake.

Here in this part of code is the correction:

//where uint32_t SystemCoreClock = 4000000; in other system source file.
void DRV_TIMER_init(void)
{
  uwPrescalerValue = (uint32_t)(SystemCoreClock / 1000000) - 1;
  TIMER_Struct.Init.Period            = 100 - 1;
  TIMER_Struct.Init.Prescaler         = uwPrescalerValue;
  TIMER_Struct.Init.ClockDivision     = 0; // these accesses work

  if (HAL_TIM_Base_Init(&TIMER_Struct) != HAL_OK)
  {
     /* Initialization Error */
     TIM_Error_Handler();
  }

  TIMER_Struct.Instance -> CR1 |= 0x01 << 3; // this works now

}

If you try to put the last sentence before the:

HAL_TIM_Base_Init(&TIMER_Struct); 

no

TIMER_Struct.Instance -> CR1 = xxx; //write mode register acces

will have effect.