My A0 pin could not give the desired output

Projects Programming
1

Overview of the project

a) To use C pointers and bit manipulation to read and manipulate bits in the hardware registers
b) To model the Analogue-to-Digital Converter (ADC) Control and Status Register A using
C Structures and Bit Fields
c) To initiate an Analogue to Digital (A to D) conversion and to use the Polling algorithm to
check/wait until the completion of the (A to D) conversion before reading the binary output
d) To generate PWM outputs with different duty cycles

The code reads an analog input from pin A0 and outputs a PWM signal on pins 3 and 11, based on the value of the input.**

When interfaced with an led from pin 3 and pin 11 one of them must be bright and the other one is dimmer and vice-versa as the resistance goes up or down

#include <avr/io.h>
#include <util/delay.h>


int main (void)
{
 
uint8_t *ddrdp, *tccr2ap, *ddrbp ,*tccr2bp, *ocr2bp ,*ocr2ap , *admuxp ,*adclp,*adchp,adcsra,upperbit,lowerbit;
uint16_t totalbit;
Serial.begin(9600);


uint8_t x; //test
  ddrdp = (uint8_t *) 0x2A; //Pin 3 (DDRD)
  ddrbp = (uint8_t *) 0x24; //Pin 11 (DDRB)
  *ddrdp = 0b00001000;
  *ddrbp = 0b00001000;


struct adcsra {
    uint8_t adps : 3; // ADC Prescaler Select Bits (least significant bit)
    uint8_t adie : 1; // ADC Interrupt Enable Bit
    uint8_t adif : 1; // ADC Interrupt Flag Bit
    uint8_t adate : 1; // ADC Auto Trigger Enable Bit
    uint8_t adsc : 1; // ADC Start Conversion Bit
    uint8_t aden : 1; // ADC Enable Bit (most significant bit)
} ;

tccr2ap = (uint8_t *) 0xB0; //TCCR2A – Timer/Counter Control Register A
  *tccr2ap = *tccr2ap & 0b00001100;
  *tccr2ap = *tccr2ap | 0b10100011;
  _delay_ms(100);


tccr2bp = (uint8_t *) 0xB1; //TCCR2B – Timer/Counter Control Register B
  *tccr2bp = *tccr2bp & 0b00110000;
  *tccr2bp = *tccr2bp | 0b00000111;
  _delay_ms(100);

ocr2ap = (uint8_t *) 0xB3; // OCR2A – Output Compare Register A
ocr2bp = (uint8_t *) 0xB4; // OCR2B – Output Compare Register B

admuxp = (uint8_t *) 0x7C;
*admuxp = *admuxp & 0b00000000;
*admuxp = *admuxp | 0b01000000; //declare analog input A0
_delay_ms(100);


adchp = (uint8_t *) 0x79; //declaring adc register-high mode
adclp = (uint8_t *) 0x78;  //declaring adc register-low mode


struct adcsra *adcsrap;
adcsrap = (struct adcsra* ) 0x7A;
_delay_ms(100);
adcsrap-> aden = 1 ;
_delay_ms(100);
adcsrap -> adps = 0b111; // 3 bits
_delay_ms(100);


while(1)
{
  
adcsrap -> adsc = 1;
  while(adcsrap -> adsc == 1)
  {
    _delay_us(1);
  }
  
upperbit = *adchp; // to obtain the data from the upper bit (2 bits)
lowerbit = *adclp; // to obtain the data from the lower bit (8 bits)
totalbit = (upperbit << 8) | lowerbit; //shifting the bit to left to make allowance for the lower bit with a total of 10 bits
x=(totalbit/1023)*255;
*ocr2ap = x +1 ;
*ocr2bp = 256-x;
_delay_ms(100);
Serial.print(totalbit); //test.
Serial.print("\n");
  }

}
2

Please edit your post, select all code and click the </> button to apply so-called code tags and next save your post. It makes it easier to read, easier to copy and the forum software will display it correctly.

Based on your topic title, does the problem only occur on A0? Or also when you change the code to use A1 or ...

3

A bunch of your pointers should be declared "volatile"...

4

alright thanks!! ive done it

5

How do i solve this issue ?

6

There is no issue on the pins but it cannot give the output that I want

7

Erm....

8

16-bit registers are typically buffered so you have to read them in a specified order.

"When ADCL is read, the ADC Data Register is not updated until ADCH is read. Consequently, if the result is left adjusted and no more than 8-bit precision is required, it is sufficient to read ADCH. Otherwise, ADCL must be read first, then ADCH."

You are reading ADCH first.

9

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