Problem reading ADC channels

Projects Programming
1

Hi There
I am currently using the Arduino UNO to read three ADC channels.
I am making use of the Arduino IDE but not the analogRead() function.

The code works well, but my problem is, the order in which the data is being printed to the serial monitor differs from the order of the code, e.g. instead of displaying 0-1-2 it displays 2-0-1. The last value is always being printed first, irrespective of the order

Any advice please.
Francois

void loop() {

ADMUX = 0b11100000; // select channel 0
delay(10); //delay 1 second
ADCSRA |= (1 << ADSC); //start single conversion
analogData = ADCH; //store data in analogData variable
float volt = (analogData/255.0)*1.1;
Serial.print(volt);
Serial.print(" ");

ADMUX = 0b11100001; // select channel 1
delay(10); //delay 1 second
ADCSRA |= (1 << ADSC); //start single conversion
analogData = ADCH; //store data in analogData variable
float volt1 = (analogData/255.0)*1.1;
Serial.print(volt1);
Serial.print(" ");

ADMUX = 0b11100010; //select channel 2
delay(10); //delay 1 second
ADCSRA |= (1 << ADSC); //start single conversion
analogData = ADCH; //store data in analogData variable
float volt2 = (analogData/255.0)*1.1;
Serial.println(volt2);

delay(1000); //delay 1 second
}

2

Any advice please.

First post all of your program after Auto formatting it in the IDE and use code tags when you post it.

3

Full code.

//8 bit adc, 3 channel

#include <avr/io.h>   //allows for register commands to be understood
int analogData;       //declare analogData variable

void setup() {
  DDRC &= ~(1 << DDC0);
  DDRC &= ~(1 << DDC1);
  DDRC &= ~(1 << DDC2);
  // ADMUX |= (1 << REFS0);   //sets reference voltage to internal ref
  // ADMUX |= (1 << REFS1);   //sets reference voltage to internal ref
  //ADMUX |= (1 << ADLAR);   //left adjusts for 8-bit resolution

  //binary format only allowed in setup because of
  //once off setup
  ADMUX = 0b11100000;   //sets 1.1V, sets ADC0 as input channel,
  //and left adjusts


  //binary format only allowed in setup because of
  //once off setup
  ADCSRA = 0b10000111;  //turn on the ADC, keep ADC single conversion mode
  //set division factor-8 for 125kHz ADC clock
  Serial.begin(9600);   //start Serial Interface
  DIDR0 = 0x07;  // disable digital input buffers on ch0 to ch2

}

void loop() {


  ADMUX = 0b11100000;  // select channel 0
  delay(10);      //delay 10 milli second
  ADCSRA |= (1 << ADSC);         //start single conversion
  analogData = ADCH;             //store 8 bit data in analogData variable
  float volt = (analogData / 255.0) * 1.1;
  Serial.print(volt);
  Serial.print("    ");

  ADMUX = 0b11100001;  // select channel 1
  delay(10);      //delay 10 milli second
  ADCSRA |= (1 << ADSC);         //start single conversion
  analogData = ADCH;             //store 8 bit data in analogData variable
  float volt1 = (analogData / 255.0) * 1.1;
  Serial.print(volt1);
  Serial.print("    ");

  ADMUX = 0b11100010;  //select channel 2
  delay(10);      //delay 10 milli second
  ADCSRA |= (1 << ADSC);         //start single conversion
  analogData = ADCH;             //store 8 bit data in analogData variable
  float volt2 = (analogData / 255.0) * 1.1;
  Serial.println(volt2);

  delay(1000);      //delay 1 second
}
4

Try this:

void loop() {

  ADMUX = 0b11100000;  // select channel 0
  delay(10);      //delay 10 milli second
  ADCSRA |= (1 << ADSC);         //start single conversion
  analogData = ADCH;             //store 8 bit data in analogData variable
  float volt = (analogData / 255.0) * 1.1;
  Serial.print("V  ");
  Serial.print(volt);
  Serial.print("    ");

  ADMUX = 0b11100001;  // select channel 1
  delay(10);      //delay 10 milli second
  ADCSRA |= (1 << ADSC);         //start single conversion
  analogData = ADCH;             //store 8 bit data in analogData variable
  float volt1 = (analogData / 255.0) * 1.1;
  Serial.print("V1  ");
  Serial.print(volt1);
  Serial.print("    ");

  ADMUX = 0b11100010;  //select channel 2
  delay(10);      //delay 10 milli second
  ADCSRA |= (1 << ADSC);         //start single conversion
  analogData = ADCH;             //store 8 bit data in analogData variable
  float volt2 = (analogData / 255.0) * 1.1;
  Serial.print("V2  "); 
  Serial.println(volt2);

  delay(1000);      //delay 1 second
}
5

You must wait for the conversion to complete, it will not be available until the ADSC bit goes
low in the ADCSRA register:

  ADCSRA |= (1 << ADSC);         //start single conversion
  while (ADCSRA & (1<<ADSC)) {}  // wait for completion
  analogData = ADCH;             //store 8 bit data in analogData variable

You can look to see how this is done in the source code for analogRead for instance (you have the
sources, its an open-source project)...

6

Mark Thanks

Problem Solved

Cois