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Comments on Declaring a callback function in `usart.h`, using it in `usart.c` but defining it in `main.c`
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Declaring a callback function in usart.h, using it in usart.c but defining it in main.c
I have written a generic device driver for a uart peripheral with a source file usart.c and a header file usart.h. I don't want a user of these files have to tamper with them.
I want to use the usart peripheral in an interrupt driven fashion, where I store the incoming byte in a ring-buffer, but I'm a unsure of the correct way to do it. I am thinking of doing it like below, by declaring the callback function in the header file, using it in the source file, and then defining what the callback function does in main.c.
/* usart.h */
...
void usart_callback();
...
/* usart.c */
#include "usart.h"
uint8_t usart_recieve()
{
/* ... */
}
ISR(USART_RX_vect) //Interrupt automatically issued when new byte in UDR0 register
{
usart_callback();
}
/* main.c */
#include "usart.h"
#define RB_SZ 32
volatile bool usart_semaphore = false;
static struct usart_rb_t
{
uint8_t buf[RB_SZ];
volatile uint8_t head;
volatile uint8_t tail;
} usart_rb;
void rb_put(uint8_t val);
void usart_callback()
{
rb_put(UDR0); //Insert byte into ring-buffer.
}
int main(void)
{
for(;;)
{
/* Program execution */
}
}
But I have a gut feeling that this is wrong. It feels wrong that I handle an intrinsic uart construct UDRE0 in main.c when it feels like it belongs in usart.c. It also feels weird to me to define a function in main.c but the place it is called is in usart.c. Almost like spaghetti. I have also prematurely defined a semaphore construct to guard against a possible race condition but have not yet figured out how to apply that correctly either.
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