About Starting ADC

[Mmee]

Hello.​

I am using the STM32L4 series.

I want to send the ADC converted sensor value to the PC via UART communication.

​

I started ADC in /* USER CODE BEGIN 2 */ zone of "main.c" output from CubeIDE, but it failed.

When the start instruction is given twice as shown below, the code is executed, but the sensor value cannot be obtained.

​

if(HAL_ADC_Start_IT(&hadc2)!=HAL_OK){ //result: TRUE

int aaa=0;

aaa=1;

if(HAL_ADC_Start_IT(&hadc2)!=HAL_OK){ //result: FALSE...why?

aaa=0;

}

}

​

I am at a loss because I have no idea what the cause is.

I am sorry to trouble you, but please reply regarding this matter.

[KnarfB]

If the result is not HAL_OK, find out what it is. And/or debug-step into the second call. HAL_ADC_Start_IT - do you have interrupt enabled and a callback?

[Mmee]

I'll try check the details of the result.

​

I have enabled ADC2, but not specifically enabled interrupts (see image).

​I am thinking to enable continuous conversion and get the value as below with timer interrupt.

​

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)

{

if(htim == &htim7){ //1ms timer

​

iAdVal=HAL_ADC_GetValue(&hadc2); �? this

sprintf(sbuff, ",%d", iAdVal);

memcpy(&td[strlen(td)],sbuff,strlen(sbuff));

cnt_tim7++;

if (cnt_tim7>=TD_CNT_MAX)

{

if(huart2.gState==HAL_UART_STATE_READY){

HAL_UART_Transmit(&huart2, (uint8_t*)td, strlen(td), 0xFFFF);

memset(td, '\0', cnt_tim7);

cnt_tim7=0;

​

}

}

}

}

[waclawek.jan]

Does the first ADC "process" finished by the time you try to run it the second time?

JW

[Mmee]

The ADC is set to continuous conversion mode. Need to care about the timing of the process?

The ADC value is obtained in the timer interrupt process.

iAdVal=HAL_ADC_GetValue(&hadc2);

[Mmee]

The ADC is set to continuous conversion mode. Need to care about the timing of the process?

The ADC value is obtained in the timer interrupt process.

iAdVal=HAL_ADC_GetValue(&hadc2);

[MM..1]

When you start IT version then ADC runs on background. Your code continues immediately to next start end return false = cant start twice.

Plus continuos mode dont need next start without any stop used.

[waclawek.jan]

> The ADC is set to continuous conversion mode.

Then why do you start it the second time?

JW

[MM..1]

When parenthes in code is ok second start never occur when first is true, But if example code is repeated then both results is false,..