ADC_HandleTypeDef* h & (h = &hadc1)

[StanCosgrove]

Hi I come across an ADC code as below, could anyone advise whats the meaning of pointer *h in the function argument and whats (h = &hadc1) do inside the callback function ?

main(void){
HAL_ADC_Start_IT(&hadc1); 
...
 while (1)
 {
 if (adc_valid == 1)
	 {
 ...
		 HAL_ADC_Start_IT(&hadc1);
	 }
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* h) 
{
	if (h = &hadc1)
	{
		adc_result = HAL_ADC_GetValue(&hadc1);
		adc_valid =1;
	}
}

 

[Andrew Neil]

---

@StanCosgrove wrote:

Hi I come across an ADC code as below,

---

Where did you find it? Please give a link.

 

---

@StanCosgrove wrote:

 what's the meaning of pointer *h in the function argument

---

That's just standard C: h is a pointer to an object of type ADC_HandleTypeDef - an ADC Handle.

See the HAL User Manual for details.

You can also select the type name, and use 'Go to definition' - there will be documentation alongside the definition.

 

---

@StanCosgrove wrote:

 what's (h = &hadc1) do inside the callback function ?

 

	if (h == &hadc1)
	{
		adc_result = HAL_ADC_GetValue(&hadc1);
		adc_valid =1;
	}

 

 

 

That looks like a classic C typo - it should most likely be '==' (ie, test for equality) not '=' (assignment)

 

	if (h == &hadc1)
	{
		adc_result = HAL_ADC_GetValue(&hadc1);
		adc_valid =1;
	}

 

 

[StanCosgrove]

yes it a typo, anyway what does the following means ? 

(h == &hadc1)

 

[Andrew Neil]

Again, standard C syntax:

It's just testing if the value of the pointer h is equal to &hadc1.

That is, it's checking that the supplied handle pointer h is pointing to the handle hadc1.

 // Is the parameter referring to hadc1?
	if (h == &hadc1)
	{
 // Yes it is - get the ADC value corresponding to hadc1
		adc_result = HAL_ADC_GetValue(&hadc1);
		adc_valid =1;
	}

 

So it will do nothing unless the supplied pointer is pointing to the Handle hadc1

which could equally be written as:

	if (h == &hadc1)
	{
		adc_result = HAL_ADC_GetValue( h );
		adc_valid =1;
	}

 

[Andrew Neil]

---

@StanCosgrove wrote:

 pointer *h

 

---

Note that the pointer is just h;

*h is dereferencing the pointer; ie, accessing the thing that the pointer points to.

[Andrew Neil]

UM2217: User Manual - Description of STM32H7 HAL and low-layer drivers:

https://www.st.com/resource/en/user_manual/um2217-description-of-stm32h7-hal-and-lowlayer-drivers-stmicroelectronics.pdf