[AVR] Atmega128 how to make several codes work together

[Justin Wenger]

I want to make several codes work together.(ex. seven segment code+ LED code+ timer code + ....)

Each code works properly on its own, but when I try to combine it, problem happens.

Only one code works even though I combined these codes together.

Code below is a code using seven segment + timer + UART at the same time,

and I want it to count it down from 30:00 to 00:00 while I can use UART at the same time.

But only the timer code works and UART code doesn't.

If you know what the problem is, please give me an advice.

#define F_CPU 1600000
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdio.h>


const unsigned char Segment_Data[] =
{0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x27,0x7F,0x6F};
char COLUMN[4]={0,0,0,0}; 

int Cnt=0;
int SHOW_NUMBER=0, SHOW_NUMBER12=30, SHOW_NUMBER34=0; 

void Show4Digit(int number);
void ShowDigit(int i, int digit);
void uart0_init(void);
int Putchar(char message);
void uart(void);
char getchar1(void);

ISR(TIMER0_OVF_vect) { // TIMER0 has overflowed
    Cnt++;
    if(Cnt==244){
        SHOW_NUMBER34--;
        Cnt=0;
    }
    if(SHOW_NUMBER34<0){
        SHOW_NUMBER12--;
        SHOW_NUMBER34=59;
    }
    if(SHOW_NUMBER12<0){  
        SHOW_NUMBER12=0;
        SHOW_NUMBER34=0;
    }
}


int main(void) {
        
        uart0_init();
        char c;
        fdevopen(Putchar, 0);
        printf("\n\rUART_Test");

    DDRC = 0xff; DDRA = 0xff; PORTC = 0x00;
    TCCR0 = 0x06; // Normal mode, prescale 256, 16M/256=62500Hz
    TCNT0 = 0x00; // n=0, 256 count, 62500Hz/256=244.14Hz
    TIMSK = 0x01; // timer0 OVERFLOW interrupt enable
    SREG |= 0x80; // Global Interrupt Enable
    while (1) {
        SHOW_NUMBER=SHOW_NUMBER12*100+SHOW_NUMBER34;
    Show4Digit(SHOW_NUMBER);

    }

}


void uart(void){
            uart0_init();
            char c;
            fdevopen(Putchar, 0);
            printf("\n\rUART_Test");
          while(1){
                      c = getchar1();
                      printf("%c", c);
                  }
}








void Show4Digit(int number) {          
    COLUMN[0] = number/1000; COLUMN[1] = (number%1000)/100;
    COLUMN[2] = (number%100)/10; COLUMN[3] = (number%10);
    for(int i=0;i<4;i++) {
        ShowDigit(COLUMN[i],i); 
        _delay_ms(2); // wait for a second
    }
}
void ShowDigit(int i, int digit) {
    PORTC=~(0x01<<digit);
    PORTA = Segment_Data[i]; 
}



void uart0_init(void) {
    UCSR0B = 0x00; //disable while setting baud rate
    UCSR0A = 0x00;
    UCSR0C = 0x06;
    UBRR0L = 0x67; //set baud rate lo
    UBRR0H = 0x00; //set baud rate hi
    UCSR0B = 0x18;
}


int Putchar(char message) {// Putchar "P" cVde
    while (((UCSR0A>>UDRE0)&0x01) == 0) ; // UDRE, data register empty
    UDR0 = message;
    return 0;
}

char getchar1(void) {
    while(!(UCSR0A&0x80));
    return UDR0;
}

 

[KlausST]

Hi,

the first you have to do:
* draw a flow chart
* decide timings

*****
General answer:
What you talk about are "tasks".
You need to provide processing time to each task.
Thus a "while (1)" within a task is a no-go, because it comsumes all processing time... not giving any processing power to other tasks.

Each task needs to check whether it needs something to do
* if yes, then do it
* if no: go to the next task
... then to the next ... to the next .. then restart the loop, beginning with the first task.

****
There are several solutions:
* timed tasks
* interrrupt driven tasks
* running a real time OS

Klaus

 

[betwixt]

Either use the UART interrupt so the serial routine is called when a character is received or poll the UART within the main() loop to see if a character has arrived.

Be careful with 'char c' being declared in both the main() and uart() routines, when you declare a variable inside a function it becomes local to that function and not outside it. You actually declare two different instances of 'c' which are both destroyed as those functions end. If you need 'c' to be available elsewhere, declare it at the top of the program and outside any function.

Brian.

 

[danadakk]

Variables modified in ISRs that are used external to ISR need to be declared
as "volatile" -

Volatile in C | Guide to How Volatile Keyword works in C with Examples

Guide to Volatile in C. Here we discuss an introduction to Volatile in C along with syntax, working and examples for better understanding.

www.educba.com

How to Use C’s Volatile Keyword

The proper use of C's volatile keyword is poorly understood by many programmers. This is not surprising, as most C texts dismiss it in a sentence or two. This article will teach you the proper way to do it.

barrgroup.com

Your "while(1)" inside main() is perfectly acceptable, common acceptable practice
as you have used it.

Your UART code inside of main() only executes once as it is not inside primary loop
in main(), the while(1) loop. Is that what you want.


Regards, Dana.