Skip to main content
Mmee
Mmee
Associate
August 22, 2020
Question

About Starting ADC

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.

This topic has been closed for replies.

8 replies

KnarfB
KnarfB
Super User
August 22, 2020

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
MmeeAuthor
Associate
August 22, 2020

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;

​

}

}

}

}

0693W000003Q2pFQAS.png

waclawek.jan
waclawek.jan
Super User
August 22, 2020

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

JW

Mmee
MmeeAuthor
Associate
August 22, 2020

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
MmeeAuthor
Associate
August 22, 2020

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
MM..1
Super User
August 22, 2020

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
waclawek.jan
Super User
August 22, 2020

> The ADC is set to continuous conversion mode.

Then why do you start it the second time?

JW

MM..1
MM..1
Super User
August 22, 2020

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,..

Terms & ConditionsAccessibility statement