A task to take values from the ADC on the arduino nano ATmega168PA

Other Hardware 3rd Party Boards
1

Hi everybody! I had a task to take values from the ADC on the arduino nano ATmega168PA. I noticed that the ADC value changes in the range of 40 values while the voltage on the multimeter is stable. What could be? How to overcome the noise problem?

2

Please show your test code and connection diagram

3

Smooth the raw data as your multimeter did.

1 Like
4 
// Подключаем библиотеки
#define F_CPU 16000000UL
#include <avr/io.h>
#include <util/delay.h>
#include <math.h>
#include <avr/interrupt.h>






// Define pins
#define HEATER_PIN PB0 // Heater pin (relay on/off)
#define CHECK_PIN PB1 // LED RED
#define TEMP_PIN PC2 // Temperature sensor pin PC2

// Define variables
//volatile float temp; // Current temperature in Celsius
volatile float u; // Control signal
volatile float I=0; // Integral component

void initADC()
{
	ADMUX = (1 << REFS1) | (1 << REFS0) | (1 << MUX1) ; // Select internal 1.1V reference and ADC5 channel
	ADCSRA = (1 << ADEN) | (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0); // Enable ADC, set prescaler to 128
}

// Initialize timer
void initTimer()
{
  TCCR1A = (1 << WGM01); // Set CTC mode
  TCCR1B = (1 << CS01) | (1 << CS00); // Set prescaler to 64
  OCR1B = 0x61A8; // Set compare match value to 25000, 100ms
  TIMSK1 = (1 << OCIE1B); // Enable compare match interrupt
}




// Interrupt service routine for timer compare match
ISR(TIMER1_COMPB_vect)
{
  uint16_t adcValue; // ADC value variable
  
  ADCSRA |= (1 << ADSC); // Start ADC conversion
  
  while(ADCSRA & (1 << ADSC)); // Wait for conversion to complete
  
  adcValue = ADCW; // Read ADC value
  Serial.println(ADCW);
  
}

// Main function
int main(void)
{
  DDRB |= (1 << HEATER_PIN); // initialization of the pin (heater) to the output
  DDRB |= (1 << CHECK_PIN); // initialization of the red test LED
   // Set the PC2 pin to read
  DDRC &= ~(1 << TEMP_PIN);
 // Turn on the internal pull-up resistor on pin PC2
  PORTC &= ~(1 << TEMP_PIN);
  
  
  Serial.begin(9600);
  initTimer();    // Initialize timer
  initADC();
  sei();      // Enable global interrupts
  
  while(1)
  {
    
    // Do other tasks if needed
    
  }
  
  return 0;
  
}
5

How to do it? I posted my code.

6

Hello roman_arduino

Take a view to gain the knowledge:

7

Your code is way overcomplicated. Why all this dances with registers, if finally your code is almost equivalent to this:

void setup() {
Serial.begin(9600);
analogReference(INTERNAL);
}
void loop() {
Serial.println(analogRead(A0));
delay(100);
}

You use 1.1v reference, so the 40 units of ADC is only +/-0.02v. Your multimeter may not notice this changes.

8

And how then to configure the program? I wanted to take values in the range from 0 (0 ADC value) to 1.1 volts (1023 ADC value).

9

Blocking code and serial I/O in interrupt context - going for all the no-nos, huh?

2 Likes
10

What do you need to configure?

11

I need that at approximately constant voltage, the ADC value shows more or less the same value.

12

I think this has nothing to do with your program and its configuration.
The voltage variations has a completely external cause.

13

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.