I have learnt C++ before at school, then C. Haven't got a formal training in C like C++, mostly self taught. The idea of using static variables and static functions are not yet clear for me. As much as i know that if a static variable is declared in a class,it is shared by all the objects of the class, and a static functions is used to work with the static variables.
But here in Joey's code i see -
/* Serial calibration program. Untested. */
#include <avr/io.h>
#include <stdio.h>
#include <util/delay.h>
static int usart_put(char c, __attribute__ ((__unused__)) FILE *stream) {
while (!(UCSRA & (1<<UDRE)));
UDR = c;
return 0;
}
int main(void) {
static FILE usart = FDEV_SETUP_STREAM(&usart_put, NULL, _FDEV_SETUP_WRITE);
stdout = &usart;
UBRRL = 51;
UCSRB = (1<<TXEN);
OSCCAL = 0;
do {
_delay_ms(50);
printf("OSCCAL=%u\r\n", OSCCAL);
_delay_ms(50);
} while (++OSCCAL);
while (1);
}
/* 9600 baud @ 8 MHz */
/* 1200 baud @ 1 MHz */
Why did he use static in the function, usart_put ( ). What are the general guidelines for a function to be static in gcc ?
Can i / should I use static in simple adc read functions like this -
int adc_read() // adc read function
{
ADCSRA|=(1<<ADSC);
while(bit_is_set(ADCSRA,ADSC));
return ADC;
}
Also, why don't we see static before functions like this -
void adc_setup() // adc setup function for ATtiny 13A
{
ADMUX|=(1<<MUX0); //Adc at pin 7
ADMUX=(1<<REFS0);
ADCSRA|=(1<<ADPS1)|(1<<ADPS0)|(1<<ADEN);
}
