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read multiple ADC without interrupt
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loutek

Posted: Jun 04, 2011 - 02:20 PM

Joined: Dec 28, 2008
Posts: 47
Location: Italy

Hi all, I want to read a multiple ADC input without using interrupt.CPU running at 8 Mhz
I use this sub:

Code:

uint16_t Read_ADC (uint8_t ch)  {

ADMUX = (1<<REFS0);   //AVCC as ADC Voltage Reference

  ADCSRA = (1<<ADEN) | (1<< ADPS2); //enable ADC, prescale 16

ch = ch&0b00000111;

ADMUX |= ch;

  ADCSRA |= (1<<ADSC);

  while (!(ADCSRA & (1<<ADIF)));

  ADCSRA |= (1<<ADIF);

  return ADC;

  }

read the input value and in main:

Code:

int main() {

   DDRB = 0xFF;

   uint16_t ADC_result = 0;

   int i;

    USART_init();

   adc_Init();

   while (1) {

      for (i = 0; i < 3; i++) { //start the scan...

         ADC_result = Read_ADC(i); //and read the result

         switch (i) { ...then i use the value to do something

.........

But nothing happens.
However if I remove the for loop and

Code:

ADC_result = Read_ADC(0);

i can read the ADC value.
Any suggestion?

thank you

clawson

Posted: Jun 04, 2011 - 02:23 PM

Joined: Jul 18, 2005
Posts: 62371
Location: (using avr-gcc in) Finchingfield, Essex, England

Not enough context. Show more of the code and explain "nothing happens" and how you are observing that.

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loutek

Posted: Jun 04, 2011 - 02:48 PM

Joined: Dec 28, 2008
Posts: 47
Location: Italy

By now i just want to read a voltage on ADC0 and ADC1 and turn on/off a led.

Code:

nt main() {

   DDRB = 0xFF;

   uint16_t ADC_result = 0;

   int i;

    USART_init();

   adc_Init();

   while (1) {

      for (i = 1; i < 3; i++) {

         ADC_result = Read_ADC(i);

         switch (i) {

         case 1:

            if (ADC_result < 120) {

               PORTB = 0x01;

            } 

            else if (ADC_result > 150) {

               PORTB = 0x00;

            }

         case 2:

            if (ADC_result < 120) {

               PORTB = 0x01;

            } 

            else if (ADC_result > 150) {

               PORTB = 0x00;

            }

         }

      }

      }

      return 0;

   }

no led is turned on/off
Thank

Koshchi

Posted: Jun 04, 2011 - 05:06 PM

Joined: Nov 17, 2004
Posts: 13853
Location: Vancouver, BC

Quote:

By now i just want to read a voltage on ADC0 and ADC1 and turn on/off a led.

Code:

for (i = 1; i < 3; i++) { 

         ADC_result = Read_ADC(i);

But this reads ACD1 and ADC2.

_________________
Regards,
Steve A.

The Board helps those that help themselves.

loutek

Posted: Jun 04, 2011 - 07:11 PM

Joined: Dec 28, 2008
Posts: 47
Location: Italy

@koshch
you're right... But not working at all

Code:

for (i=0; i 2; i++)

i'll try another solution...

Visovian

Posted: Jun 04, 2011 - 08:43 PM

Joined: Aug 07, 2007
Posts: 1478
Location: Czech

deleted

Visovian

Posted: Jun 04, 2011 - 08:58 PM

Joined: Aug 07, 2007
Posts: 1478
Location: Czech

Quote:

ADMUX = (1<<REFS0); //AVCC as ADC Voltage Reference
ADCSRA = (1<<ADEN) | (1<< ADPS2); //enable ADC, prescale 16
ch = ch&0b00000111;
ADMUX |= ch;

Error, look here
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=107120&highlight=

loutek

Posted: Jun 27, 2011 - 10:19 AM

Joined: Dec 28, 2008
Posts: 47
Location: Italy

Thank you all...
Ok... Reading other posts it is better to use interrupt.
So that's my way:

Code:

/*

 ATmega16 @ 8 Mhz 

 PORTA as ADC

 PORTB leds

           */

#include <avr/io.h>

#include <avr/interrupt.h>

#include <inttypes.h>

volatile uint8_t adc_result[8];

volatile uint8_t input = 0; // both var. volatite because shared by main and ISR ...clawson FAQ #1 

void ADC_init(void);

int main(void) {

   DDRB = 0xFF; // PORTB as Out

   ADC_init();  //init ADC

   sei(); // enable all interrupts

   ADCSRA |= (1 << ADSC); // first ADC conversion

   while (1) {

      if (adc_result[0] > 150) {

         PORTB = 0x01;

      } else if (adc_result[0] < 150) {

         PORTB = 0x00;

      }

      if (adc_result[1] > 150) {

         PORTB = 0x02;

      } else if (adc_result[1] < 150) {

         PORTB = 0x00;

      }

   }

   return 0;

}

ISR( ADC_vect ) {

   adc_result[input] = ADCH; // input 0, first result, 8 bits

   if (input < 8)

   input++;

   else

   input = 0;

   ADMUX |= input; // next input

   ADCSRA |= ( 1 << ADSC ); // next conversion

}

void ADC_init() {

    ADMUX |= (1 << ADLAR) | (1 << REFS0); // left adj. and AVcc as reference

   ADCSRA = (1 << ADEN) | (1 << ADIE) | (1 << ADPS2); // Enable ADC, interrupt, prescaler 16

}

...but I can't see any led on. Sad

clawson

Posted: Jun 27, 2011 - 10:41 AM

Joined: Jul 18, 2005
Posts: 62371
Location: (using avr-gcc in) Finchingfield, Essex, England

Quote:

ADMUX |= input; // next input

You never clear the previous channel setting. Suggest you use:

Code:

ADMUX = (1 << ADLAR) | (1 << REFS0) | channel;

_________________

indianajones11

Posted: Jun 27, 2011 - 11:11 AM

Joined: Nov 28, 2004
Posts: 3553
Location: San Diego, Ca

Also, one time code should be done... once . Put

Code:

ADMUX = (1<<REFS0);   //AVCC as ADC Voltage Reference 

  ADCSRA = (1<<ADEN) | (1<< ADPS2); //enable ADC, prescale 16

in your adc_init() ( which you already did, so no need to repeat the same stuff ). It's just a waste of time / memory to do it the way you did .

Your code with the switch is not right, time to open your C book and look at that.

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loutek

Posted: Jun 27, 2011 - 07:35 PM

Joined: Dec 28, 2008
Posts: 47
Location: Italy

Hello, when I start debuging the changed code

Code:

#include <avr/io.h>

#include <avr/interrupt.h>

#include <inttypes.h>

volatile uint8_t adc_result[8];

volatile uint8_t input = 0; // both var. volatite because shared by main and ISR ...clawson FAQ #1

int main(void) {

   DDRB = 0xFF; // PORTB as Out

   ADMUX |= (1 << ADLAR) | (1 << REFS0); // left adj. and AVcc as reference

   ADCSRA = (1 << ADEN) | (1 << ADIE) | (1 << ADPS2); // Enable ADC, interrupt, prescaler 16

   sei(); // enable all interrupts 

   ADCSRA |= (1 << ADSC); // first ADC conversion

   while (1) {

      if (adc_result[0] > 120) {

         PORTB = 0x01;

      } else if (adc_result[0] < 120) {

         PORTB = 0x00;

      }

      if (adc_result[1] > 120) {

         PORTB = 0x02;

      } else if (adc_result[1] < 120) {

         PORTB = 0x00;

      }

   }

   return 0;

}

ISR( ADC_vect ) {

   adc_result[input] = ADCH; // input 0, first result, 8 bits

   if (input < 8)

   input++;

   else

   input = 0;

   ADMUX |= (input & 0x07); // next input and mask the bits

   ADCSRA |= ( 1 << ADSC ); // next conversion

     }

I can see in the I/O view no ADSC setted by

Code:

ADCSRA |= (1 << ADSC); // first ADC conversion

instruction
I think code is correct but I can't check where is my error or what I can't understand.

Thank you

clawson

Posted: Jun 27, 2011 - 07:41 PM

Joined: Jul 18, 2005
Posts: 62371
Location: (using avr-gcc in) Finchingfield, Essex, England

Quote:

I start debuging

Simulator or real hardware debugging?

_________________

loutek

Posted: Jun 27, 2011 - 07:46 PM

Joined: Dec 28, 2008
Posts: 47
Location: Italy

...real hardware debugging. I test hardware too and things work... i think it's a programming issue..
Thank you very much for reply.

clawson

Posted: Jun 27, 2011 - 07:59 PM

Joined: Jul 18, 2005
Posts: 62371
Location: (using avr-gcc in) Finchingfield, Essex, England

Quote:

ADMUX |= (input & 0x07); // next input and mask the bits

This is not right - you are NOT clearing the previous channel selection - presumably you did not understand my previous answer?

_________________

indianajones11

Posted: Jun 27, 2011 - 10:43 PM

Joined: Nov 28, 2004
Posts: 3553
Location: San Diego, Ca

I doubt that you put a breakpoint and then single-stepped into the ADSC being set, because you didn't see it , but you didn't say the ISR DIDN'T fire , OR that you didn't get adc_values . If you run the debugger at full speed, there's plenty you'll miss, if that's what you're doing .

Anyway, you're bouncing all around with these code versions and it's not a good move to go from non-working code to a more complex non-working version ( ISR ).

How are ALL your MCU adc pins connected and which debugger do you use ? Put adc_result in the watch window and breakpoint after it should get a value in the ISR .

You don't see any LEDs on, but only superman could since it would be too fast for you to see . You have no delays for when it's on / off .

_________________
1) Studio 4.18 build 716 (SP3)
2) WinAvr 20100110
3) PN, all on Doze XP... For Now
A) Avr Dragon ver. 1
B) Avr MKII ISP, 2009 model
C) MKII JTAGICE ver. 1

loutek

Posted: Jun 29, 2011 - 02:27 PM

Joined: Dec 28, 2008
Posts: 47
Location: Italy

to clear the previus channel:

Code:

 
ISR( ADC_vect ) {

   for (input=0; input <8; input++) {

        input = ADMUX;

        input &= 0x07;

        adc_result[input] = ADCH;

        ADMUX++;

      ADCSRA |= (1 << ADSC); // next ADC conversion

     }

    ADMUX &= 0xF0;

    }

Now if a simulator debug i can see ADSC setted, in real debug with avr dragon no ADSC is setted Confused

clawson

Posted: Jun 29, 2011 - 02:29 PM

Joined: Jul 18, 2005
Posts: 62371
Location: (using avr-gcc in) Finchingfield, Essex, England

Your code makes no sense whatsoever?!?

_________________

loutek

Posted: Jun 29, 2011 - 02:37 PM

Joined: Dec 28, 2008
Posts: 47
Location: Italy

Quote:

Your code makes no sense whatsoever?!?

...Ok I give it up...

Kartman

Posted: Jun 29, 2011 - 03:14 PM

Joined: Dec 30, 2004
Posts: 8789
Location: Melbourne,Australia

Go back to your original code and fix the problems. Have you read the datasheet onthe part you're using? It is all pretty simple, but you're making some fundamental mistakes.

JohanEkdahl

Posted: Jun 29, 2011 - 04:05 PM

Joined: Mar 27, 2002
Posts: 18599
Location: Lund, Sweden

In your latest code, what is the point with doing

Code:

ADMUX++;

?
Youre at the end of the loop, just about to iterate and increment input which will then be assigned to ADMUX.

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