task 23 switch case.ino

#include <util/delay.h>
#include <avr/io.h>  //allows for register commands to be understood

//Store at least 1000 result in a ring buffer (unsigned integers arrays): Done
//sample rate 200sample/s DONE
//External 5V at AREF: DONE
//Left Adjust ADC: DONE
//Use only 8 bit resolution: DONE
//Use ADC prescalar factor to 128: DONE

//Modify the circuit layout DONE
//Implement push button with two states: 1 to records and 2 to send data to PC
//Reset buffer when turn state 2 to 1
//Blink LED to show status
//Use PUTTY tools for input logging

#define S0 0
#define S1 1

// Declare variables
volatile bool state;
volatile bool read_on;
volatile uint8_t val;
volatile uint16_t reading;
volatile float voltage;

//Declare variable for ring buffer
#define SIZE_OF_BUFFER 5
volatile int start = -1;
int volatile end = -1;
uint8_t volatile database[SIZE_OF_BUFFER] = { 0 };

// Check if the array is full
bool isFull() {
  if ((start == (end + 1)) || ((start == 0) && (end == SIZE_OF_BUFFER - 1))) {
    return 1;
  }
  return 0;
}

//Add value to array
void add(uint8_t value) {
  if (start == -1) {
    start = 0;
  }
  end = (end + 1) % SIZE_OF_BUFFER;
  database[end] = value;
}

//Remove value from array
void removeFirst() {
  if (start == end) {
    start = -1;
    end = -1;
  } else {
    start = (start + 1) % SIZE_OF_BUFFER;
  }
}

//Interrupt actions
ISR(TIMER1_COMPA_vect) {
  read_on = 1;
}

ISR(INT0_vect) {
  //Serial.println("Enter button ISR...");
  state = !state;

  //Serial.println("Exit button ISR...");
  //Serial.print("State is ");
  //Serial.println(state);
}

int main(void) {
  cli();

  // Set Pin 2 on Port D to read
  DDRD &= ~(1 << DDD2);

  //Set Left Adjust (8 bit ADC)
  ADMUX |= (1 << ADLAR);

  // Start the ADC, and set the LSBs in ADCSRA to 111, which corresponds to a division factor of 128. This should give us 200Sa/s
  ADCSRA |= 0b10000111;  // ADCSRA |= (1 << ADPS0)|(1 << ADPS1)|(1 << ADPS2)|(1 << ADEN);

  //Set timer
  TCCR1B |= (1 << WGM12);               //CTC Mode
  TCCR1B |= (1 << CS11) | (1 << CS10);  //Set prescalar to 64
  TCNT1 = 0;                            //Initialise timer to 0
  TCCR1A |= (1 << COM1A0);              //OC1A is toggled on match
  OCR1A = 1250;                         //Set compare value Correspond to 200Hz count
  TIMSK1 |= (1 << OCIE1A);              //Enable CTC interrupt for OCR1A

  //Set external interupt 0 (push button)
  EICRA |= (1 << ISC00) | (1 << ISC01);
  EIMSK |= (1 << INT0);

  sei();

  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);

  state = 1;
  read_on = 0;

  // the loop routine runs over and over again forever:
  while (1) {

    switch (state) {
      case S0:
        // Write
        for (int i = start; i < SIZE_OF_BUFFER + start; i++) {  // Check whether 2nd statement needs to be i != end + 1 or something
          count = i % SIZE_OF_BUFFER;

          reading = (database[count] << 2) | (0b11);
          voltage = reading * 5.0 / 1023.0;

          Serial.println(voltage);
          //_delay_ms(5);
        }

        start = -1;
        end = -1;

        read_on = 0;
        //Serial.println("End data readout...");
      case S1:
        // Read
        //Serial.println("Reading...");
        ADCSRA |= (1 << ADSC);  //start conversion
        //Use Ring Buffer to store data

        val = ADCH;
        if (isFull()) {
          removeFirst();
          add(val);
        } else {
          add(val);
        }

        // print out the value you read:
        //Serial.println(database[end]);
    }
  }
}