Hi, I am trying to obtain values from potentiomater which is connected to PA0 (ADC channel 0), through ADC.

[BMoha.19.45]

However, the values that I obtain (I show them on LCD display) are not only inconsistent, but also the potentiometer's rotation doesn't effect the value? I have searched a lot and tried different ways but I couldn't find the problem in my code. Please, can you help me where I did wrong? I have attached the related part of the code with comments.

GPIOA->MODER |= GPIO_MODER_MODE0_Msk; //Set as PA0 as Analog Mode
	
RCC->APB2ENR |= RCC_APB2ENR_ADC1EN; //Enable the ADC clock
	
ADC1->SQR1 = 0x00000000; //1 Convertion
ADC1->SQR2 = 0x00000000; 
ADC1->SQR3 = 0x00000000; //0'th channel will be converted first
	
ADC1->SMPR2 = 0x00000005; //sampling time - 112 cycles
ADC1->CR2 |= ADC_CR2_CONT_Msk; //Enable continious mode
ADC1->CR1 &= ~(ADC_CR1_SCAN_Msk); //Disable Scan mode
ADC1->CR2 |= ADC_CR2_ADON; //Enable ADC
	
while(1)
{
	ADC1->CR2 |= ADC_CR2_SWSTART_Msk; //Start convertion
	LCDSendAnInteger((ADC1->DR), 7); //Display value in LCD
	notExactTimeDelay(1000000);
	LCDClearDisplay();
}

[waclawek.jan]

What STM32? What board?

Read back the GPIO and ADC registers content and check.

JW

[S.Ma]

Make sure no pull-up/down resistor activated, ADC calibration was done, and put a decoupling cap at the ADC input pin to avoid voltage droop during sampling time. What value is your potentiometer? ADC input should be low impedence.

[BMoha.19.45]

Thank you for your answer. I use STM32F407VG discovery board. I read the datasheet many times and check each registers' content very carefully, but no effect.

[BMoha.19.45]

Thank you for your answer. I use STM32f407VG discovery board and it does ADC calibration automatically. My potentiometer value is 10k.

[S.Ma]

Add a cap to ground on adc input pin to stabilize the voltage, 100nF maybe? When sampling the adc briefly looks like RC filter R about 3kohm and discharged cap of few pF

[BMoha.19.45]

Is my code above alright? Because, even when I unplug the jumper cable from PA0 it shows the same values.

[brian239955_stm1]

You are trying to display the conversion result before the conversion is complete. You need something like -

while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET) {

;

}

before reading ADC1->DR and sending to the LCD.

[AvaTar]

> You are trying to display the conversion result before the conversion is complete.

True, but for a continuous conversion, this doesn't make much of a difference. Except for the lag.

But waiting for the conversion result (as suggested) and reducing the delay would make a more responsive display.

But in your place, I would swap to another AIN channel. PA0 on the F4 Discovery is connected to the User Button.

[BMoha.19.45]

I added the while loop and also change the channel to channel 1, but the same :pensive_face: