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#include <stddef.h>
#include <stdio.h>
#include <avr/interrupt.h>
#include "task/sched.h"
#include "io/usart.h"
#include "bug/debug.h"
#include "mcu/task/context.h"
static struct usart_device_t umain = USART_DEVICE_INIT(umain);
static int umain_putc(char c);
static int umain_getc();
FILE umain_out = FDEV_SETUP_STREAM(umain_putc, NULL, _FDEV_SETUP_WRITE);
FILE umain_in = FDEV_SETUP_STREAM(NULL, umain_getc, _FDEV_SETUP_READ);
void usart_init(unsigned long baud) {
UCSR0A |= (1 << U2X0); //enable double speed transmission
uint16_t baud_setting = (F_CPU / 4 / baud - 1) / 2;
UBRR0H = baud_setting >> 8;
UBRR0L = baud_setting;
UCSR0B |= (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0); // 8-bit, no parity, 1 stop bit
UCSR0B &= ~(1 << UDRIE0);
stdout = &umain_out;
stdin = &umain_in;
}
int umain_putc(char c) {
if (c == '\n') umain_putc('\r');
int r = 0;
do {
cli();
r = rbuffer_write_char(&umain.tx_buffer, c);
sei();
UCSR0B |= (1 << UDRIE0);
} while (r != 1);
return c;
}
int umain_getc() {
while (rbuffer_empty(&umain.rx_buffer)) {
cli();
sleep_queue(&umain.rx_queue);
yield();
}
cli();
char c = 0;
size_t r = rbuffer_read_char(&umain.rx_buffer, &c);
sei();
if (r) return (int) c;
else return EOF;
}
//called when byte is received
ISR(USART0_RX_vect, ISR_NAKED) {
context_save();
char c = UDR0;
rbuffer_write_char(&umain.rx_buffer, c);
wake_all_queue(&umain.rx_queue);
context_restore();
asm volatile ("reti");
}
//called when data register is empty
ISR(USART0_UDRE_vect) {
char c;
if (rbuffer_read_char(&umain.tx_buffer, &c)) {
UDR0 = c;
} else {
UCSR0B &= ~(1 << UDRIE0); //buffer empty, disable interruot
}
}
/*
void serial_read() {
ENTER_CRITICAL();
list_move_tail(¤t->list, &serial_rx_q);
EXIT_CRITICAL();
yield();
}
*/
/*
void serial_write_str(const char* const str) {
for (size_t i = 0; str[i] != '\0'; ++i) {
ENTER_CRITICAL();
rbuffer_write(&serial_dev.tx_buffer, str[i]);
EXIT_CRITICAL();
UCSR0B |= (1 << UDRIE0);
}
}*/
/*
ISR(INT3_vect, ISR_NAKED) {
SAVE_CONTEXT();
if (!list_empty(&serial_rx_q)) {
list_move_tail(serial_rx_q.next, &ready);
}
schedule();
RESTORE_CONTEXT();
asm volatile ("reti");
}
*/
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