2019-04-23 10:56 AM
I do not know if and what I am doing wrong. I am using CubeMX and a Nucleo 64-Board. This is the while inside the main:
while (1)
{
if(HAL_ADC_PollForConversion(&hadc, 1000) == HAL_OK){
adc_value[i] = HAL_ADC_GetValue(&hadc);
media += ((float)adc_value[i++])/n_amostras;
r = 0.02*media;
v = 0.04*media;
comp = 52.91*media;
if(i == n_amostras){
i = 0;
media = 0;
}
}
}
I do not know if the PollForConversion is the best option, I just used because I saw it in a tutorial in youtube. I need to calculate these values 'r', 'v' and 'comp'. One of my problems is that the ADC is not so accurate as I would like, I would appreciate suggestions about how I could improve this. Also sometimes it does not work as it should, but this could be a problem in my circuit. the values become random, apparently. I will also show the configuration of the ADC:
static void MX_ADC_Init(void)
{
/* USER CODE BEGIN ADC_Init 0 */
/* USER CODE END ADC_Init 0 */
ADC_ChannelConfTypeDef sConfig = {0};
/* USER CODE BEGIN ADC_Init 1 */
/* USER CODE END ADC_Init 1 */
/**Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
*/
hadc.Instance = ADC1;
hadc.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
hadc.Init.Resolution = ADC_RESOLUTION_12B;
hadc.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc.Init.ScanConvMode = ADC_SCAN_DIRECTION_FORWARD;
hadc.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
hadc.Init.LowPowerAutoWait = DISABLE;
hadc.Init.LowPowerAutoPowerOff = DISABLE;
hadc.Init.ContinuousConvMode = ENABLE;
hadc.Init.DiscontinuousConvMode = DISABLE;
hadc.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
hadc.Init.DMAContinuousRequests = DISABLE;
hadc.Init.Overrun = ADC_OVR_DATA_OVERWRITTEN;
if (HAL_ADC_Init(&hadc) != HAL_OK)
{
Error_Handler();
}
/**Configure for the selected ADC regular channel to be converted.
*/
sConfig.Channel = ADC_CHANNEL_1;
sConfig.Rank = ADC_RANK_CHANNEL_NUMBER;
sConfig.SamplingTime = ADC_SAMPLETIME_71CYCLES_5;
if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN ADC_Init 2 */
HAL_ADCEx_Calibration_Start(&hadc);
/* USER CODE END ADC_Init 2 */
}
I also used the calibration function of the HAL library here, but I do not if I am using it in the right way.
2019-04-23 11:39 AM
Hi
index i , has always the same value. was this your intention?
if i is different than n_amostras then the inside loop "if" statement will never be true.
2019-04-23 12:09 PM
True and also what is the input analog impedence of what is connected... unless there is an external op-amp in follower mode.
Otherwise, ADC result will be lower than expected... and more unstable.
2019-04-24 04:51 AM
It was not my intention, it is corrected now.
2019-04-24 05:02 AM
Input impedance, S&H capacity and sampling time are interrelated. I guess you know how to deal with it, design-wise.
I suggest to validate the ADC channels first,, by applying known (and different) voltages to all channels, and check the values - either via some output, or in the debugger.