I am trying to send characters(unsigned char) using the USART of the atemga328P to a virtual terminal setup in proteus. I am using the Arduino uno with the atmega328p.The code is below. below it is the link to screen shot of the proteus simulation.

I want the program to work such that when I press the button after starting the simulation, it will print HELLO! and wait. Then if i press the button again then it should display WORLD and toggle between these two words every time I press the button. In between each letter I want to create a 200ms delay.

The problem I am facing is after I start the proteus simulation, only the first letter “H” ( it is inside the transmit1() function) of is displayed. (I think the program keeps looping inside the while loop defined inside the DELAY() function.) Even if I press the button nothing changes.

It works when I call the _delay_ms() using the library, instead of DELAY(); function I made. But in this case even before I press the button and call the START() function, HELLO! is displayed in the terminal with the start of the simulation.

I am trying to use the 16-bit Timer/Counter1 to make a delay function (DELAY();) which can be called in between transmissions.
I am using the external interrupt to trigger the the transmissions by calling the START(); function. I have connected a button to the INT0 pin in the Arduino uno board to trigger the interrupt.

I am newbie to embedded programming . I am using Atmel Studio 7 to write the code and generate the hex file.
I would really appreciate if someone can help me out….!

#define F_CPU 16000000UL
#define BAUD 9600
#define UBRR_Value ((F_CPU/16/BAUD)-1)
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

int volatile toggle = 0;
int volatile toggle2 = 0;


void USART_CONFIG(void){
    
    //baude rate set
    UBRR0H = (unsigned char)(UBRR_Value>>8);
    UBRR0L = (unsigned char)UBRR_Value;
    
    //enable transmitter:UCSR0B
    UCSR0B |= (1<<TXEN0);
    //set frame format: 8bits data, 1 stop bit
    UCSR0C |= (1<<UCSZ01)|(1<<UCSZ00);
    
}

void TIMER_CONFIG(void){
        TCCR1B |= (1<<WGM12)|(1<<CS12);//ctc mode set,prescaler 256
        OCR1AH = 0x30;
        OCR1AL =0xD4; //set for one second
        TIMSK1 |=(1<<OCIE1A); //enable timer compare interrupt
        TCNT1 = 0;
}

ISR(TIMER1_COMPA_vect){
    toggle2 = 0;
    TCCR1B &= 0B11111011; //stopping the counter
}

void BUTTON_CONFIG(void){screenshot of the proteus simulation
    
    //external interrupt enable on PD2 INT0
    EIMSK |= 0B00000001;
    //interrupt set for rising edge
    EICRA |= 0B00000011;
    
    
}



void DELAY(void){
    TIMER_CONFIG();
    toggle2 = 1;
    while(toggle2 == 1){
        //looping in this until toggle2 will be zero by the ISR
    }
    return;
}

void transmitDATA(unsigned char data){
    while (!(UCSR0A & (1<<UDRE0))){
        //waiting until transmit buffer is empty
    }
    UDR0 = data;
    return;
}

void transmit1(void){
    
    transmitDATA('H');
    DELAY();
    transmitDATA('E');
    DELAY();
    transmitDATA('L');
    DELAY();
    transmitDATA('L');
    DELAY();
    transmitDATA('O');
    DELAY();
    transmitDATA('!');
    return;
}


void transmit2(){
    transmitDATA('W');
    DELAY();
    transmitDATA('O');
    DELAY();
    transmitDATA('R');
    DELAY();
    transmitDATA('L');
    DELAY();
    transmitDATA('D');
    DELAY();
    return;
}



void START(void){
        //if toggle==1 then transmit1
        if(toggle == 1){
            transmit1();
            }else{
        //if toggle ==0 then tranmit2   
            transmit2();
        }
}

ISR(INT0_vect){
    toggle = 1-toggle;
    START();
}

int main(void)
{   
    
    //configure the USART transmitter
    USART_CONFIG();
    //configure the external interrupt
    BUTTON_CONFIG();
    //enable global interrupts
    sei();
    while (1) 
    {   
    }   
    return 0;
}

screenshot of the proteus simulation

It works if there is no external interrupt. That means; If i put don’t include a button feature to toggle between words and let the program to run in infinite while loop. the DELAY() works. I have mentioned below how the START() function and the main function will look like then. in this case the BUTTON_CONFIG() function which configure external interrupt is commented.

void START(void){
    while(1){
        //if toggle==1 then transmit1
        if(toggle == 1){
            transmit1();
            }else{
        //if toggle ==0 then tranmit2   
            transmit2();
        }
    }
}

int main(void)
{   
    
    //configure the USART transmitter
    USART_CONFIG();
    //configure the external interrupt
    //BUTTON_CONFIG();
    //enable global interrupts
    sei();
    START();
    while (1) 
    {   
    }   
    return 0;
}